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9L0-623 exam Dumps Source : Mac OS X Deployment 10.6

Test Code : 9L0-623
Test title : Mac OS X Deployment 10.6
Vendor title : Apple
: 64 actual Questions

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Apple Mac OS X Deployment

Deploying smart contract to Rinkeby testnet using Truffle and mac OS X | killexams.com actual Questions and Pass4sure dumps

Testnet as a site to check your judicious solutions

There will live 2 articles about deploying judicious contracts:

  • relocating contract from watch at various RPC to Rinkeby testnet using truffle and Mac OS
  • Connecting to deployed contract the use of Infura. (In growth)
  • Introduction

    Testnet is a spot to watch at various your judicious contracts solutions. in reality, it’s a clone of the Ethereum network that lets you install and verify your sensible contracts devoid of paying steady charges.

    There are a few leading testnets:

    Metamask capture
  • Ropsten check community — Proof-of-Work (PoW)
  • Kovan examine network — Proof-of-Authority (PoA)
  • Rinkeby watch at various community — Proof-of-Authority (PoA)
  • right here’s a bit of on distinct consensus protocols.

    One step left to birth! before relocating your contract to Testnet, gain positive you Have got set aside in geth, truffle and Mist.

    set up contract from examine RPC to testnet (Rinkeby)

    first off, to installation your assignment, you must down load the whole rinkeby node (containing transactions via clients for uncouth of the time).

    To download uncouth chain records:

  • Open your finder, for illustration at documents.
  • Create current folder, rename it as “rinkeby” and open it.
  • Create a current folder interior rinkeby and contact it as “chaindata”.
  • Open your terminal and Go to documents/rinkeby with command:
  • $ cd files/rinkeby/
  • after which to down load uncouth chain data evade next command:
  • $ geth --datadir=./chaindata --rinkeby

    you will behold whatever thing enjoy this:

    mind about this url. it's your path_to_your_ipc_file
  • replica path_to_your_ipc_file somewhere.
  • growth of chain downloading you're going to find in subsequent step in Mist.

    brief Tip: Parameter — rinkeby says to geth that chain facts has to live downloaded from rinkeby testnet.

    Create a verify pockets with Mist and rinkeby network

    adequate, they Have to pay for deploying out contract, so they want create ethereum account, as a result of they should pay for this toil with gas (don’t worry they will pay for now not actual money). So Mist will succor us to try this.

    brief Tip: Mist is an ethereum client the site that you can create your current wallets or manage them. extra about it you could find here.

  • To open Mist which should live connected to their rinkeby community they can use command (see instance beneath):
  • $ /path_to_your_application_/Contents/MacOS/Mist --rpc /path_to_your_ipc_file

    path_to_your_ipc_file — that you would live able to find it originally of this article.

    I Have installed Mist into my functions. So in my case it appears enjoy this:

    $ /purposes/Mist.app/Contents/MacOS/Mist --rpc /clients/bomalkevych/documents/rinkeby/chaindata/geth.ipc

    After this command you'll behold Mist’s banner:

    Mist starting (rinkeby community)
  • faucet on «LAUNCH application». (In some cases it will besides live launched automatically)
  • In my case, uncouth packets had been downloaded (1.655.084)

    Then, you are going to behold within the left bottom corner how a Great deal chain packets Have been downloaded. it may possibly seize you from a few minutes to a few hours depending on your internet connection and the pass plenty friends are linked to testnetwork.

    quick Tip: in case you want to behold downloading status with out Mist which you can connect to connection (connection which you opened during step 1) and check it out in a terminal.

    So, to try this:

  • Open a current terminal window (CMD + T)
  • Run subsequent command to connect to the connection:
  • $ geth connect /path_to_your_ipc_file

    path_to_your_ipc_file — that you may find it at the start of this article.

    once more, in my case it appears like:

    $ geth attach /users/bomalkevych/documents/rinkeby/chaindata/geth.ipc
  • at terminal during this tab of terminal evade next command:
  • $ eth.syncing

    it will probably revert whatever thing enjoy this:

    currentBlock: 13445,highestBlock: 1604086,knownStates: 32228,pulledStates: 19524,startingBlock: 0

    What means what remaining shroud became loaded or can revert «false» what capability that complete chain became loaded.

    Create a brand new wallet

    when you Have one that you may skip this step. a pass to create a brand current wallet and manage money step-by pass of-step that you can determine privilege here.

    adding funds to a check account

    all over their chain is loading, they will add some ether to their account. To conclude that, you must:

  • Open Mist, select your pockets, and duplicate it’s handle.
  • copy tackle, replica anyway

    There are some short and pellucid suggestions a pass to accept dollars. In several words:

  • select some convivial network: fb, google+ or Twitter.
  • Make a set aside up with the tackle wallet you copied earlier than.
  • reproduction link to the set aside up you made.
  • Paste it within the enter container on https://www.rinkeby.io/#faucet (see monitor).
  • Add funds to your wallet
  • Wait whereas a shroud along with your transaction may live introduced to blockchain register (it could actually seize a few minutes). To check fame of your transaction use etherscan.
  • Etherscan

    to peer details of your account transactions (background, statuses and so forth).

  • Go to https://rinkeby.etherscan.io
  • Paste your wallet number as proven on display:
  • Scan transaction particulars
  • Open some transaction and notice fame. outcome should quiet live like:
  • instance of transaction particulars set up contract with Truffle

    When syncing will cease (in first tab):

  • Go to first tab in terminal and wreck syncing with (manage+C) which they evade privilege through first step.
  • Run command:
  • $ geth --datadir=./chaindata --rinkeby --rpc --rpcapi db,eth,web,web3,very own
  • Open your undertaking’s truffle.js file.
  • change from parameter in code below with your pockets quantity and paste it on your truffle.js.
  • rinkeby: host: "localhost",port: 8545,network_id: "4", // Rinkeby identification 4from: "0x99a4572656eb49FFEEFbe9588f8e7ab0F8D6Eb5e", // account from which to deploygas: 6712390

    In my case, it feels enjoy this:

    remember! change from together with your pockets handle.

    next step is to connect to the energetic connection they did at the begining of this section and unlock their account. as a pass to conclude this:

  • Open a brand current terminal window (CMD + T)
  • Run subsequent command to connect to the connection:
  • $ geth connect --rpc /path_to_your_ipc_file

    path_to_your_ipc_file — you could find it in the genesis of this article.

    once more, in my case it seems like:

    $ geth connect /clients/bomalkevych/documents/rinkeby/chaindata/geth.ipc
  • finally during this tab of terminal evade next command (as a substitute of 0x99a4572656eb49FFEEFbe9588… paste your wallet number):
  • $ personal.unlockAccount("0x99a4572656eb49FFEEFbe9588...")
  • input account password and press Enter. (it can revert “genuine”)
  • Open a brand current tab in the terminal and Go to your venture folder in terminal.
  • eventually to installation your contract, use command:
  • $ truffle migrate --community rinkeby Troubleshooting

    First: if you wish to redeploy your contract and you accept a message enjoy this:

    the use of community 'rinkeby'.community up thus far.

    are trying to delete construct folder and evade command once again.

    2d: if you accept oversight message uncouth over deploing which related to gasoline limit.

    verify your truffle.js file you set aside fuel cost as: 6712390


    Apple issues macOS 10.14.3 Supplemental replace | killexams.com actual Questions and Pass4sure dumps

    Apple on Thursday updated macOS Mojave with the unencumber of the macOS 10.14.3 Supplemental replace. The update become launched together with the iOS 12.1.four replace.

    The Supplemental replace fixes the community FaceTime malicious program that has been making headlines these days. while most americans affiliate the worm with the iPhone, group FaceTime succor is accessible on macOS Mojave. The replace besides fixes a security problem involving are living photographs in FaceTime. The security notes for the Supplemental update can live found online.

    before installing any device update, office a backup of your records. listed below are the steps for the setting up.

    1. within the Finder, click on the Apple menu and search for an replace indication for gadget Preferences, as shown in the photo below. in case you behold an indication for an update, select system Preferences.

    sytem preference update mojaveIDG

    If now not, opt for About This Mac > Overview > application update.

    2. you should definitely live on the window for utility replace. Your Mac will investigate on-line to watch if the update is attainable. if it is, click on the update Now button.

    3. A warning will appear, declaring that your Mac will exigency to restart. click down load & Restart if you can proceed. The down load will seize a yoke of minutes and your Mac will instantly restart.

    in case your Mac doesn’t restart, Go returned to the application update window and click on the update Now button. A Restart button may additionally appear. click on it to proceed.

    To handle upon this article and other Macworld content, dispute with their facebook web page or their Twitter feed.

    Mac Deployment equipment: an silhouette of the top-quality tips on how to Roll Out a brand current Mac Lab or replace an historic One | killexams.com actual Questions and Pass4sure dumps

    New Macs, current models of Mac OS X, current utility, and current school years uncouth translate to at least one component for Mac IT personnel: picking the optimal strategy to roll out the current computer systems, software, classrooms, or configurations. Ryan Faas gives you a top flush view of the variety of tools accessible from Apple and third parties, and tells you how to roll out with less bother and fewer complications.

    Like this article? They recommend 

    Deployments are piece of lifestyles for IT team of workers, live they deployments of current workstations, current applications or different configuration alterations, or deployments of entire current labs and networks. these working in schooling often expend the times earlier than a college year or current faculty semester readying lecture rooms and desktop labs by means of doing laptop cleanup and updates (almost, wiping the difficult drives of workstations after which deploying a brand current device configuration onto them). unfortunately, deployments can both live trouble-free or riddled with complications without both confiscate planning and the proper tools. this article makes a speciality of the rectify materiel for Mac IT cadaver of workers charged with planning and managing deployments and rollouts.

    There are a few tools and methods that are, through this aspect, regarded tried and actual, including the venerable Apple application fix in both network and indigenous disk diversifications (together with a yoke of GUI entrance ends to ease the deployment process), Mac OS X Server’s NetInstall function, Apple far flung laptop, and the open source Radmind utility. additionally included are pc administration materiel corresponding to FileWave and NetOctopus. We’ll appear in brief at each alternative, its methodology, and its pros and cons for numerous types of deployments.

    Apple utility repair (ASR) has been a appliance for Mac directors and technicians for just about twenty years. In Mac OS X, ASR is a command-line appliance that is a component of every Mac OS X unencumber. ASR uses disk pictures created with the Apple Disk Utility (or the very device) as a supply of target workstations. it may well overwrite an existing disk with a specific photo. as a result of disk images comprehend a completely configured device (Mac OS X, installed software, device configuration, and so on), ASR allows you to promptly installation study-to-use workstations. It isn't, however, a very first rate device for making use of software updates or rolling out a unique or constrained quantity of purposes.

    ASR can use a disk photograph saved on a local disk (such as a difficult compel or CD/DVD) as a source for deployments or it may possibly use a disk graphic it is kept on a server. Being a command-line software, it is viable to initiate ASR operations remotely. despite the fact, since the target difficult drive or partition might live overwritten as a piece of the ASR technique, workstations should live begun from another Mac OS X boot disk (customarily an exterior tough compel or alternate partition).

    to gain use of a disk image as a supply for ASR, the photo should first live "scanned" with the ASR software. The scanning technique optimizes the picture for use with ASR and might reorder parts of the photograph for quicker copying. reckoning on the measurement of the photo, this technique could gain the effort.


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    Siri Deployed on Mac OS X via Air decree | killexams.com actual questions and Pass4sure dumps

    Developer Avatron Software has released a two-piece utility that allows anyone who uses an iPhone and a Mac to deploy Siri Dictation on Mac OS X. The only entrap is that you really exigency the current iPhone 4S model which features the Siri assistant.

    The benefit here is to accept Siri Dictation working on your Mac: “Like Siri on your iPhone 4S? You'll enjoy it even more on your Mac,” says Avatron. “With Air Dictate, you can enter text on your computer by talking into your iPhone 4S. It's that simple.”

    So, for instance, if you want to decree text into Mail, Pages, Microsoft Word, and even Apple’s own TextEdit app, uncouth you exigency is the Air decree app on your iPhone 4S and the Air decree Receiver app on your Mac. From there on, just pair the two and start talking.

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    - Launch any app that allows text input. For example: TextEdit, Mail, Pages, Microsoft Word.

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    To avoid any confusion (that may rise on the piece of drooling iDevice owners hoping this is some kindhearted of hack that puts Siri on their older iPhones), Air decree runs only on an iPhone 4S, and requires iOS 5.0. The app costs $0.99 (0.79 EUR).

    Air decree Receiver requires a Mac running at least Mac OS X 10.6.8 (Snow Leopard) and is free to download.

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    Mac OS X 10.6 Snow Leopard: the Ars Technica review | killexams.com actual questions and Pass4sure dumps

    Mac OS X 10.6 Snow Leopard: the Ars Technica review reader comments 454 with 269 posters participating, including legend author Share this story
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  • Mac OS X 10.4 Tiger: 150+  current featuresMac OS X 10.4 Tiger: 150+ current features

    In June of 2004, during the WWDC keynote address, Steve Jobs revealed Mac OS X 10.4 Tiger to developers and the public for the first time. When the finished product arrived in April of 2005, Tiger was the biggest, most important, most feature-packed release in the history of Mac OS X by a wide margin. Apple's marketing drive reflected this, touting "over 150 current features."

    All those current features took time. Since its introduction in 2001, there had been at least one major release of Mac OS X each year. Tiger took over a year and a half to arrive. At the time, it definitely seemed worth the wait. Tiger was a hit with users and developers. Apple took the lesson to heart and quickly set expectations for the next major release of Mac OS X, Leopard. Through various channels, Apple communicated its objective to Move from a 12-month to an 18-month release cycle for Mac OS X. Leopard was officially scheduled for "spring 2007."

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    Steve Jobs at WWDC 2007, touting 300  current features in Mac OS X 10.5 LeopardSteve Jobs at WWDC 2007, touting 300 current features in Mac OS X 10.5 Leopard

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    Mac OS X appeared to live maturing. The progression was clear: longer release cycles, more features. What would Mac OS X 10.6 live like? Would it arrive three and a half years after Leopard? Would it and comprehend 500 current features? A thousand?

    At WWDC 2009, Bertrand Serlet announced a Move that he described as "unprecedented" in the PC industry.

    Mac OS X 10.6 - Read Bertrand's lips: No  current Features!Mac OS X 10.6 - Read Bertrand's lips: No current Features!

    That's right, the next major release of Mac OS X would Have no current features. The product title reflected this: "Snow Leopard." Mac OS X 10.6 would merely live a variant of Leopard. Better, faster, more refined, more... uh... snowy.

    This was a risky strategy for Apple. After the rapid-fire updates of 10.1, 10.2, and 10.3 followed by the riot of current features and APIs in 10.4 and 10.5, could Apple really accept away with calling a "time out?" I imagine Bertrand was really sweating this announcement up on the stage at WWDC in front of a live audience of Mac developers. Their reaction? impulsive applause. There were even a few hoots and whistles.

    Many of these very developers applauded the "150+ current features" in Tiger and the "300 current features" in Leopard at past WWDCs. Now they were applauding zero current features for Snow Leopard? What explains this?

    It probably helps to know that the "0 current Features" skid came at the discontinuance of an hour-long presentation detailing the major current APIs and technologies in Snow Leopard. It was besides quickly followed by a back-pedaling ("well, there is one current feature...") skid describing the addition of Microsoft Exchange support. In isolation, "no current features" may seem to imply stagnation. In context, however, it served as a developer-friendly affirmation.

    The overall message from Apple to developers was something enjoy this: "We're adding a ton of current things to Mac OS X that will succor you write better applications and gain your existing code evade faster, and we're going to gain positive that uncouth this current stuff is rock-solid and as bug-free as possible. We're not going to overextend ourselves adding a raft of current customer-facing, marketing-friendly features. Instead, we're going to concentrate 100% on the things that handle you, the developers."

    But if Snow Leopard is a affection note to developers, is it a Dear John note to users? You know, those people that the marketing department might so crudely refer to as "customers." What's in it for them? Believe it or not, the sales pitch to users is actually quite similar. As exhausting as it has been for developers to preserve up with Apple's seemingly never-ending stream of current APIs, it can live just as taxing for customers to abide on top of Mac OS X's features. Exposé, a current Finder, Spotlight, a current Dock, Time Machine, a current Finder again, a current iLife and iWork almost every year, and on and on. And as much as developers detest bugs in Apple's APIs, users who experience those bugs as application crashes Have just as much intuition to live annoyed.

    Enter Snow Leopard: the release where they uncouth accept a fracture from the new-features/new-bugs treadmill of Mac OS X development. That's the pitch.

    Uncomfortable realities

    But wait a second, didn't I just mention an "hour-long presentation" about Snow Leopard featuring "major current APIs and technologies?" When speaking to developers, Apple's message of "no current features" is another pass of saying "no current bugs." Snow Leopard is supposed to fix traditional bugs without introducing current ones. But nothing says "new bugs, coming privilege up" quite enjoy major current APIs. So which is it?

    Similarly, for users, "no current features" connotes stability and reliability. But if Snow Leopard includes enough changes to the core OS to fill an hour-long overview session at WWDC more than a year before its release, can Apple really gain benign on this promise? Or will users discontinuance up with uncouth the disadvantages of a feature-packed release enjoy Tiger or Leopard—the inevitable 10.x.0 bugs, the unfamiliar, untried current functionality—but without any of the actual current features?

    Yes, it's enough to gain one quite cynical about Apple's actual motivations. To pitch some more fuel on the fire, Have a watch at the Mac OS X release timeline below. Next to each release, I've included a list of its most significant features.

    Mac OS X release timelineMac OS X release timeline

    That curve is taking on a decidedly droopy shape, as if it's being weighed down by the ever-increasing number of current features. (The releases are distributed uniformly on the Y axis.) Maybe you judge it's reasonable for the time between releases to stretch out as each one brings a heavier load of goodies than the last, but preserve in mind the ratiocinative consequence of such a curve over the longhorn haul.

    And yeah, there's a itsy-bitsy upwards kick at the discontinuance for 10.6, but remember, this is supposed to live the "no current features" release. Version 10.1 had a similar no-frills focus but took a heck of a lot less time to arrive.

    Looking at this graph, it's difficult not to sensation if there's something siphoning resources from the Mac OS X evolution effort. Maybe, say, some project that's in the first two or three major releases of its life, quiet in that steep, early section of its own timeline graph. Yes, I'm talking about the iPhone, specifically iPhone OS. The iPhone traffic has exploded onto Apple's balance sheets enjoy no other product before, even the iPod. It's besides accruing developers at an alarming rate.

    It's not a stretch to imagine that many of the artists and developers who piled on the user-visible features in Mac OS X 10.4 and 10.5 Have been reassigned to iPhone OS (temporarily or otherwise). After all, Mac OS X and iPhone OS partake the very core operating system, the very language for GUI development, and many of the very APIs. Some workforce migration seems inevitable.

    And let's not forget the "Mac OS X" technologies that they later learned were developed for the iPhone and just happened to live announced for the Mac first (because the iPhone was quiet a secret), enjoy Core Animation and code signing. Such collusion theories certainly aren't helped by WWDC keynote snubs and other indignities suffered by Mac OS X and the Mac in universal since the iPhone arrived on the scene. And so, on top of everything else, Snow Leopard is tasked with restoring some luster to Mac OS X.

    Got uncouth that? A nearly two-year evolution cycle, but no current features. Major current frameworks for developers, but few current bugs. Significant changes to the core OS, but more reliability. And a franchise rejuvenation with few user-visible changes.

    It's enough to whirl a leopard white.

    The cost of entry

    Snow Leopard's opening overture to consumers is its price: $29 for those upgrading from Leopard. The debut release of Mac OS X 10.0 and the terminal four major releases Have uncouth been $129, with no special pricing for upgrades. After eight years of this kindhearted of fiscal disciplining, Leopard users may well live tempted to stop reading privilege now and just Go pick up a copy. Snow Leopard's upgrade cost is well under the impulse purchase threshold for many people. Twenty-nine dollars plus some minimal flush of faith in Apple's aptitude to help the OS with each release, and boom, instant purchase.

    Still here? Good, because there's something else you exigency to know about Snow Leopard. It's an overture of a different sort, less of a come-on and more of a spur. Snow Leopard will only evade on Macs with Intel CPUs. Sorry (again), PowerPC fans, but this is the discontinuance of the line for you. The transition to Intel was announced over four years ago, and the terminal current PowerPC Mac was released in October 2005. It's time.

    But if Snow Leopard is meant to prod the PowerPC holdouts into the Intel age, its "no current features" stance (and the accompanying want of added visual flair) is working against it. For those running Leopard on a PowerPC-based Mac, there's precious itsy-bitsy in Snow Leopard to succor push them over the (likely) four-digit cost wall of a current Mac. For PowerPC Mac owners, the threshold for a current Mac purchase remains mostly unchanged. When their traditional Mac breaks or seems too slow, they'll Go out and buy a current one, and it'll foster with Snow Leopard pre-installed.

    If Snow Leopard does discontinuance up motivating current Mac purchases by PowerPC owners, it will probably live the result of resignation rather than inspiration. An Intel-only Snow Leopard is most significant for what it isn't: a further extension of PowerPC life uphold on the Mac platform.

    The final touching group is owners of Intel-based Macs that are quiet running Mac OS X 10.4 Tiger. Apple shipped Intel Macs with Tiger installed for a itsy-bitsy over one year and nine months. Owners of these machines who never upgraded to Leopard are not eligible for the $29 upgrade to Snow Leopard. They're besides apparently not eligible to purchase Snow Leopard for the traditional $129 price. Here's what Apple has to shriek about Snow Leopard's pricing (emphasis added).

    Mac OS X version 10.6 Snow Leopard will live available as an upgrade to Mac OS X version 10.5 Leopard in September 2009 [...] The Snow Leopard unique user license will live available for a suggested retail cost of $29 (US) and the Snow Leopard Family Pack, a unique household, five-user license, will live available for a suggested cost of $49 (US). For Tiger® users with an Intel-based Mac, the Mac Box Set includes Mac OS X Snow Leopard, iLife® '09 and iWork® '09 and will live available for a suggested cost of $169 (US) and a Family Pack is available for a suggested cost of $229 (US).

    Ignoring the family packs for a moment, this means that Snow Leopard will either live free with your current Mac, $29 if you're already running Leopard, or $169 if you Have an Intel Mac running Tiger. People upgrading from Tiger will accept the latest version of iLife and iWork in the contract (if that's the confiscate term), whether they want them or not. It positive seems enjoy there's an obvious site in this lineup for a $129 offering of Snow Leopard on its own. Then again, perhaps it uncouth comes down to how, exactly, Apple enforces the $29 Snow Leopard upgrade policy.

    (As an aside to non-Mac users, note that the non-server version of Mac OS X has no per-user serial number and no activation scheme of any kind, and never has. "Registration" with Apple during the Mac OS X install process is entirely optional and is only used to collect demographic information. Failing to register (or entering entirely bogus registration information) has no outcome on your aptitude to evade the OS. This is considered a genuine edge of Mac OS X, but it besides means that Apple has no answerable record of who, exactly, is a "legitimate" owner of Leopard.)

    One possibility was that the $29 Snow Leopard upgrade DVD would only install on top of an existing installation of Leopard. Apple has done this character of thing before, and it bypasses any proof-of-purchase annoyances. It would, however, interpolate a current problem. In the event of a difficult drive failure or simple determination to reinstall from scratch, owners of the $29 Snow Leopard upgrade would live forced to first install Leopard and then install Snow Leopard on top of it, perhaps more than doubling the installation time—and quintupling the annoyance.

    Given Apple's history in this area, no one should Have been surprised to find out that Apple chose the much simpler option: the $29 "upgrade" DVD of Snow Leopard will, in fact, install on any supported Mac, whether or not it has Leopard installed. It will even install onto an entirely vacuous difficult drive.

    To live clear, installing the $29 upgrade to Snow Leopard on a system not already running a properly licensed copy of Leopard is a violation of the end-user license agreement that comes with the product. But Apple's determination is a refreshing change: rewarding honest people with a hassle-free product rather than trying to castigate dishonest people by treating everyone enjoy a criminal. This "honor system" upgrade enforcement policy partially explains the immense jump to $169 for the Mac Box Set, which ends up re-framed as an honest person's pass to accept iLife and iWork at their accustomed prices, plus Snow Leopard for $11 more.

    And yes, speaking of installing, let's finally accept on with it.

    Installation

    Apple claims that Snow Leopard's installation process is "up to 45% faster." Installation times vary wildly depending on the speed, contents, and fragmentation of the target disk, the quicken of the optical drive, and so on. Installation besides only happens once, and it's not really an touching process unless something goes terribly wrong. Still, if Apple's going to gain such a claim, it's worth checking out.

    To liquidate as many variables as possible, I installed both Leopard and Snow Leopard from one difficult disk onto another (empty) one. It should live noted that this change negates some of Snow Leopard's most vital installation optimizations, which are focused on reducing random data access from the optical disc.

    Even with this disadvantage, the Snow Leopard installation took about 20% less time than the Leopard installation. That's well short of Apple's "up to 45%" claim, but behold above (and don't forget the "up to" weasel words). Both versions installed in less than 30 minutes.

    What is striking about Snow Leopard's installation is how quickly the initial Spotlight indexing process completed. Here, Snow Leopard was 74% faster in my testing. Again, the times are petite (5:49 vs. 3:20) and again, current installations on vacuous disks are not the norm. But the shorter wait for Spotlight indexing is worth noting because it's the first indication most users will accept that Snow Leopard means traffic when it comes to performance.

    Another notable thing about installation is what's not installed by default: Rosetta, the facility that allows PowerPC binaries to evade on Intel Macs. Okay Apple, they accept it. PowerPC is a stiff, bereft of life. It rests in peace. It's rung down the curtain and joined the choir invisible. As far as Apple is concerned, PowerPC is an ex-ISA.

    But not installing Rosetta by default? That seems a itsy-bitsy harsh, even foolhardy. What's going to occur when uncouth those users upgrade to Snow Leopard and then double-click what they've probably long since forgotten is a PowerPC application? Perhaps surprisingly, this is what happens:

    Rosetta: auto-installed for your convenienceRosetta: auto-installed for your convenience

    That's what I saw when I tried to launch Disk Inventory X on Snow Leopard, an application that, yes, I had long since forgotten was PowerPC-only. After I clicked the "Install" button, I actually expected to live prompted to insert the installer DVD. Instead, Snow Leopard reached out over the network, pulled down Rosetta from an Apple server, and installed it.

    Rosetta auto-install

    No reboot was required, and Disk Inventory X launched successfully after the Rosetta installation completed. Mac OS X has not historically made much use of the install-on-demand approach to system software components, but the facility used to install Rosetta appears quite robust. Upon clicking "Install," an XML property list containing a vast catalog of available Mac OS X packages was downloaded. Snow Leopard uses the very facility to download and install printer drivers on demand, saving another trip to the installer DVD. I hope this technique gains even wider use in the future.

    Installation footprint

    Rosetta aside, Snow Leopard simply puts fewer bits on your disk. Apple claims it "takes up less than half the disk space of the previous version," and that's no lie. A clean, default install (including fully-generated Spotlight indexes) is 16.8 GB for Leopard and 5.9 GB for Snow Leopard. (Incidentally, these numbers are both powers-of-two measurements; behold sidebar.)

    A gigabyte by any other name

    Snow Leopard has another trick up its sleeve when it comes to disk usage. The Snow Leopard Finder considers 1 GB to live equal to 109 (1,000,000,000) bytes, whereas the Leopard Finder—and, it should live noted, every version of the Finder before it—equates 1 GB to 230 (1,073,741,824) bytes. This has the outcome of making your difficult disk suddenly appear larger after installing Snow Leopard. For example, my "1 TB" difficult drive shows up in the Leopard Finder as having a capacity of 931.19 GB. In Snow Leopard, it's 999.86 GB. As you might Have guessed, difficult disk manufacturers use the powers-of-ten system. It's uncouth quite a mess, really. Though I foster down pretty firmly on the powers-of-two side of the fence, I can't failing Apple too much for wanting to match up nicely with the long-established (but quiet dumb, mind you) difficult disk vendors' capacity measurement standard.

    Snow Leopard has several weight loss secrets. The first is obvious: no PowerPC uphold means no PowerPC code in executables. Recall the maximum workable binary payload in a Leopard executable: 32-bit PowerPC, 64-bit PowerPC, x86, and x86_64. Now cross half of those architectures off the list. Granted, very few applications in Leopard included 64-bit code of any kind, but it's a 50% reduction in size for executables no matter how you slice it.

    Of course, not uncouth the files in the operating system are executables. There are data files, images, audio files, even a itsy-bitsy video. But most of those non-executable files Have one thing in common: they're usually stored in compressed file formats. Images are PNGs or JPEGs, audio is AAC, video is MPEG-4, even preference files and other property lists now default to a compact binary format rather than XML.

    In Snow Leopard, other kinds of files climb on board the compression bandwagon. To give just one example, ninety-seven percent of the executable files in Snow Leopard are compressed. How compressed? Let's look:

    % cd Applications/Mail.app/Contents/MacOS % ls -l Mail -rwxr-xr-x@ 1 root wheel 0 Jun 18 19:35 Mail

    Boy, that's, uh, pretty small, huh? Is this really an executable or what? Let's check their assumptions.

    % file Applications/Mail.app/Contents/MacOS/Mail Applications/Mail.app/Contents/MacOS/Mail: empty

    Yikes! What's going on here? Well, what I didn't disclose you is that the commands shown above were evade from a Leopard system looking at a Snow Leopard disk. In fact, uncouth compressed Snow Leopard files appear to contain zero bytes when viewed from a pre-Snow Leopard version of Mac OS X. (They watch and act perfectly timehonored when booted into Snow Leopard, of course.)

    So, where's the data? The itsy-bitsy "@" at the discontinuance of the permissions string in the ls output above (a feature introduced in Leopard) provides a clue. Though the Mail executable has a zero file size, it does Have some extended attributes:

    % xattr -l Applications/Mail.app/Contents/MacOS/Mail com.apple.ResourceFork: 0000 00 00 01 00 00 2C F5 F2 00 2C F4 F2 00 00 00 32 .....,...,.....2 0010 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ (184,159 lines snipped) 2CF610 63 6D 70 66 00 00 00 0A 00 01 FF FF 00 00 00 00 cmpf............ 2CF620 00 00 00 00 .... com.apple.decmpfs: 0000 66 70 6D 63 04 00 00 00 A0 82 72 00 00 00 00 00 fpmc......r.....

    Ah, there's uncouth the data. But wait, it's in the resource fork? Weren't those deprecated about eight years ago? Indeed they were. What you're witnessing here is yet another addition to Apple's favorite file system hobbyhorse, HFS+.

    At the dawn of Mac OS X, Apple added journaling, symbolic links, and difficult links. In Tiger, extended attributes and access control lists were incorporated. In Leopard, HFS+ gained uphold for difficult links to directories. In Snow Leopard, HFS+ learns another current trick: per-file compression.

    The presence of the com.apple.decmpfs attribute is the first hint that this file is compressed. This attribute is actually hidden from the xattr command when booted into Snow Leopard. But from a Leopard system, which has no erudition of its special significance, it shows up as modest as day.

    Even more information is revealed with the succor of Mac OS X Internals guru Amit Singh's hfsdebug program, which has quietly been updated for Snow Leopard.

    % hfsdebug /Applications/Mail.app/Contents/MacOS/Mail ... compression magic = cmpf compression character = 4 (resource fork has compressed data) uncompressed size = 7500336 bytes

    And positive enough, as they saw, the resource fork does indeed contain the compressed data. Still, why the resource fork? It's uncouth piece of Apple's usual, ingenious backward-compatibility gymnastics. A recent illustration is the pass that difficult links to directories pomp up—and function—as aliases when viewed from a pre-Leopard version of Mac OS X.

    In the case of a HFS+ compression, Apple was (understandably) unable to gain pre-Snow Leopard systems read and interpret the compressed data, which is stored in ways that did not exist at the time those earlier operating systems were written. But rather than letting applications (and users) running on pre-10.6 systems choke on—or worse, corrupt through modification—the unexpectedly compressed file contents, Apple has chosen to conceal the compressed data instead.

    And where can the complete contents of a potentially great file live hidden in such a pass that pre-Snow Leopard systems can quiet copy that file without the loss of data? Why, in the resource fork, of course. The Finder has always correctly preserved Mac-specific metadata and both the resource and data forks when touching or duplicating files. In Leopard, even the lowly cp and rsync commands will conclude the same. So while it may live a itsy-bitsy bit spooky to behold uncouth those "empty" 0 KB files when looking at a Snow Leopard disk from a pre-Snow Leopard OS, the haphazard of data loss is small, even if you Move or copy one of the files.

    The resource fork isn't the only site where Apple has decided to smuggle compressed data. For smaller files, hfsdebug shows the following:

    % hfsdebug /etc/asl.conf ... compression magic = cmpf compression character = 3 (xattr has compressed data) uncompressed size = 860 bytes

    Here, the data is petite enough to live stored entirely within an extended attribute, albeit in compressed form. And then, the final frontier:

    % hfsdebug /Volumes/Snow Time/Applications/Mail.app/Contents/PkgInfo ... compression magic = cmpf compression character = 3 (xattr has inline data) uncompressed size = 8 bytes

    That's right, an entire file's contents stored uncompressed in an extended attribute. In the case of a benchmark PkgInfo file enjoy this one, those contents are the four-byte classic Mac OS character and creator codes.

    % xattr -l Applications/Mail.app/Contents/PkgInfo com.apple.decmpfs: 0000 66 70 6D 63 03 00 00 00 08 00 00 00 00 00 00 00 fpmc............ 0010 FF 41 50 50 4C 65 6D 61 6C .APPLemal

    There's quiet the very "fpmc..." preamble seen in uncouth the earlier examples of the com.apple.decmpfs attribute, but at the discontinuance of the value, the expected data appears as modest as day: character code "APPL" (application) and creator code "emal" (for the Mail application—cute, as per classic Mac OS tradition).

    You may live wondering, if this is uncouth about data compression, how does storing eight uncompressed bytes plus a 17-byte preamble in an extended attribute save any disk space? The retort to that lies in how HFS+ allocates disk space. When storing information in a data or resource fork, HFS+ allocates space in multiples of the file system's allocation shroud size (4 KB, by default). So those eight bytes will seize up a minimum of 4,096 bytes if stored in the traditional way. When allocating disk space for extended attributes, however, the allocation shroud size is not a factor; the data is packed in much more tightly. In the end, the actual space saved by storing those 25 bytes of data in an extended attribute is over 4,000 bytes.

    But compression isn't just about saving disk space. It's besides a classic illustration of trading CPU cycles for decreased I/O latency and bandwidth. Over the past few decades, CPU performance has gotten better (and computing resources more plentiful—more on that later) at a much faster rate than disk performance has increased. Modern difficult disk seek times and rotational delays are quiet measured in milliseconds. In one millisecond, a 2 GHz CPU goes through two million cycles. And then, of course, there's quiet the actual data transfer time to consider.

    Granted, several levels of caching throughout the OS and hardware toil mightily to conceal these delays. But those bits Have to foster off the disk at some point to fill those caches. Compression means that fewer bits Have to live transferred. Given the almost comical glut of CPU resources on a modern multi-core Mac under timehonored use, the total time needed to transfer a compressed payload from the disk and use the CPU to decompress its contents into remembrance will quiet usually live far less than the time it'd seize to transfer the data in uncompressed form.

    That explains the potential performance benefits of transferring less data, but the use of extended attributes to store file contents can actually gain things faster, as well. It uncouth has to conclude with data locality.

    If there's one thing that slows down a difficult disk more than transferring a great amount of data, it's touching its heads from one piece of the disk to another. Every Move means time for the head to start moving, then stop, then ensure that it's correctly positioned over the desired location, then wait for the spinning disk to set aside the desired bits beneath it. These are uncouth real, physical, touching parts, and it's incredible that they conclude their dance as quickly and efficiently as they do, but physics has its limits. These motions are the actual performance killers for rotational storage enjoy difficult disks.

    The HFS+ volume format stores uncouth its information about files—metadata—in two primary locations on disk: the Catalog File, which stores file dates, permissions, ownership, and a host of other things, and the Attributes File, which stores "named forks."

    Extended attributes in HFS+ are implemented as named forks in the Attributes File. But unlike resource forks, which can live very great (up to the maximum file size supported by the file system), extended attributes in HFS+ are stored "inline" in the Attributes File. In practice, this means a limit of about 128 bytes per attribute. But it besides means that the disk head doesn't exigency to seize a trip to another piece of the disk to accept the actual data.

    As you can imagine, the disk blocks that gain up the Catalog and Attributes files are frequently accessed, and therefore more likely than most to live in a cache somewhere. uncouth of this conspires to gain the complete storage of a file, including both its metadata in its data, within the B-tree-structured Catalog and Attributes files an overall performance win. Even an eight-byte payload that balloons to 25 bytes is not a concern, as long as it's quiet less than the allocation shroud size for timehonored data storage, and as long as it uncouth fits within a B-tree node in the Attributes File that the OS has to read in its entirety anyway.

    There are other significant contributions to Snow Leopard's reduced disk footprint (e.g., the removal of unnecessary localizations and "designable.nib" files) but HFS+ compression is by far the most technically interesting.

    Installer intelligence

    Apple makes two other touching promises about the installation process:

    Snow Leopard checks your applications to gain positive they're compatible and sets aside any programs known to live incompatible. In case a power outage interrupts your installation, it can start again without losing any data.

    The setting aside of "known incompatible" applications is undoubtedly a response to the "blue screen" problems some users encountered when upgrading from Tiger to Leopard two years ago, which was caused by the presence of incompatible—and some would shriek "illicit"—third-party system extensions. I Have a decidedly pragmatic view of such software, and I'm joyous to behold Apple taking a similarly practical approach to minimizing its impact on users.

    Apple can't live expected to detect and disable uncouth potentially incompatible software, of course. I suspect only the most approved or highest profile risky software is detected. If you're a developer, this installer feature may live a benign pass to find out if you're on Apple's sh*t list.

    As for continuing an installation after a power failure, I didn't Have the guts to test this feature. (I besides Have a UPS.) For long-running processes enjoy installation, this kindhearted of added robustness is welcome, especially on battery-powered devices enjoy laptops.

    I mention these two details of the installation process mostly because they highlight the kinds of things that are workable when developers at Apple are given time to polish their respective components of the OS. You might judge that the installer team would live hard-pressed to foster up with enough to conclude during a nearly two-year evolution cycle. That's clearly not the case, and customers will garner the benefits.

    Snow Leopard's current looks

    I've long yearned for Apple to gain a cleanly break, at least visually, from Mac OS X's Aqua past. Alas, I will live waiting a bit longer, because Snow Leopard ushers in no such revolution. And yet here I am, beneath a familiar-looking section heading that seems to testify otherwise. The veracity is, Snow Leopard actually changes the appearance of nearly every pixel on your screen—but not in the pass you might imagine.

    Since the dawn of color on the Macintosh, the operating system has used a default output gamma correction value of 1.8. Meanwhile, Windows—aka the ease of the world—has used a value of 2.2. Though this may not seem significant to anyone but professional graphics artists, the dissimilarity is usually apparent to even a casual observer when viewing the very image on both kinds of displays side by side.

    Though Mac users will probably instinctively prefer the 1.8 gamma image that they're used to, Apple has decided that this historical dissimilarity is more wretchedness than it's worth. The default output gamma correction value in Snow Leopard is now 2.2, just enjoy everyone else. Done and done.

    If they notice at all, users will likely experience this change as a sentiment that the Snow Leopard user interface has a bit more contrast than Leopard's. This is reinforced by the current default desktop background, a re-drawn, more saturated version of Leopard's default desktop. (Note that these are two entirely different images and not an attempt to demonstrate the effects of different gamma correction settings.)

    LeopardLeopard Snow LeopardSnow Leopard Dock Exposé spotlight effectDock Exposé spotlight effect

    But even beyond color correction, steady to form, Apple could not resist adding a few graphical tweaks to the Snow Leopard interface. The most apparent changes are related to the Dock. First, there's the current "spotlight" watch triggered by a click-and-hold on an application icon in the Dock. (This activates Exposé, but only for the windows belonging to the application that was clicked. More later.)

    Furthermore, any and uncouth pop-up menus on the Dock—and only on the Dock—have a unique watch in Snow Leopard, complete with a custom selection appearance (which, for a change, does a passable job of matching the system-wide selection appearance setting).

    New Dock menu appearance. Mmmm… arbitrary.New Dock menu appearance. Mmmm… arbitrary.

    For Mac users of a inevitable age, these menus may bring to mind Apple's Hi-Tech appearance theme from the bad-old days of Copland. They're actually considerably more subtle, however. Note the translucent edges which accentuate the rounded corners. The gradient on the selection highlight is besides admirably restrained.

    Nevertheless, this is an entirely current watch for a unique (albeit commonly used) application, and it does clash a bit with the default "slanty, shiny shelf" appearance of the Dock. But I've already had my shriek about that, and more. If the oath of Snow Leopard's appearance was to "first, conclude no harm," then I judge I'm inclined to give it a passing grade—almost.

    If I had to characterize what's wrong with Snow Leopard's visual additions with just two words, it'd live these: everything fades. Apple has sprinkled Core Animation fairy dust over seemingly every application in Snow Leopard. If any piece of the user interface appears, disappears, or changes in any significant way, it's accompanied by an animation and one or more fades.

    In moderation, such effects are fine. But in several instances, Snow Leopard crosses the line. Or rather, it crosses my line, which, it should live noted, is located far inside the territories of Candy Land. Others with a much lower tolerance for animations who are already galled by the frippery in Leopard and earlier releases will find itsy-bitsy to affection in Snow Leopard's visual changes.

    The one that really drove me over the edge is the fussy itsy-bitsy dance of the filename area that occurs in the Finder (surprise!) when renaming a file on the desktop. There's just something about so many cross-fades, color changes, and text offsets occurring so rapidly and concentrated into such a petite area that makes me want to scream. And whether or not I'm actually waiting for these animations to finish before I can continue to use my computer, it certainly feels that pass sometimes.

    Still, I must unenthusiastically call that most timehonored people (i.e., the ones who will not read this entire article) will either find these added visual touches delightful, or (much more likely) not notice them at all.

    Branding

    Animation aside, the visual sameness of Snow Leopard presents a bit of a marketing challenge for Apple. Even beyond the obvious problem of how to promote an operating system upgrade with "no current features" to consumers, there's the issue of how to accept people to notice that this current product exists at all.

    In the run-up to Snow Leopard's release, Apple stuck to a modified version of Leopard's outer space theme. It was in the keynote slideshows, on the WWDC banners, on the developer release DVDs, and uncouth over the Mac OS X section of Apple's website. The header image from Apple's Mac OS X webpage as of a week before Snow Leopard's release appears below. It's pretty nick and dried: outer space, stars, moneyed purple nebula, lens flare.

    Snow. The final frontier.Snow. The final frontier.

    Then came the golden master of Snow Leopard, which, in a pleasant change from past releases, was distributed to developers a few weeks before Snow Leopard hit the shelves. Its installer introduced an entirely different watch which, as it turns out, was carried over to the retail packaging. For a change, let's line up the discs instead of the packaging (which is rapidly shrinking to barely pen the disc anyway). Here's Mac OS X 10.0 through 10.6, top to bottom and left to right. (The 10.0 and 10.1 discs looked essentially identical and Have been coalesced.)

    One of these things is not  enjoy the others…One of these things is not enjoy the others…

    Yep, it's a snow leopard. With actual snow on it. It's a bit on the nose for my taste, but it's not without its charms. And it does Have one immense thing going for it: it's immediately recognizable as something current and different. "Unmistakable" is how I'd sum up the packaging. Eight years of the giant, centered, variously adorned "X" and then boom: a cat. There's itsy-bitsy haphazard that anyone who's seen Leopard sitting on the shelf of their local Apple store for the past two years will fail to notice that this is a current product.

    (If you'd enjoy your own picture of Snowy the snow leopard (that's right, I've named him), Apple was kindhearted enough to comprehend a desktop background image with the OS. Self-loathing Windows users may download it directly.)

    Warning: internals ahead

    We've arrived at the start of the customary "internals" section. Snow Leopard is uncouth about internal changes, and this is reflected in the content of this review. If you're only interested in the user-visible changes, you can skip ahead, but you'll live missing out on the meat of this review and the heart of Apple's current OS.

    64-bit: the road leads ever on

    Mac OS X started its journey to 64-bit back in 2003 with the release of Panther, which included the bare minimum uphold for the then-new PowerPC G5 64-bit CPU. In 2005, Tiger brought with it the aptitude to create steady 64-bit processes—as long as they didn't link with any of the GUI libraries. Finally, Leopard in 2007 included uphold for 64-bit GUI applications. But again, there was a caveat: 64-bit uphold extended to Cocoa applications only. It was, effectively, the discontinuance of the road for Carbon.

    Despite Leopard's seemingly impressive 64-bit bona fides, there are a few more steps before Mac OS X can achieve complete 64-bit nirvana. The diagrams below illustrate.

    64-bit in Mac OS X 10.4 Tiger 64-bit in Mac OS X 10.5 Leopard 64-bit in Mac OS X 10.6 Snow Leopard Mac OS X 10.4 Tiger Mac OS X 10.5 Leopard Mac OS X 10.6 Snow Leopard

    As we'll see, uncouth that yellow in the Snow Leopard diagram represents its capability, not necessarily its default mode of operation.

    K64

    Snow Leopard is the first version of Mac OS X to ship with a 64-bit kernel ("K64" in Apple's parlance), but it's not enabled by default on most systems. The intuition for this this is simple. Recall that there's no "mixed mode" in Mac OS X. At runtime, a process is either 32-bit or 64-bit, and can only load other code—libraries, plug-ins, etc.—of the very kind.

    An vital class of plug-ins loaded by the kernel is device drivers. Were Snow Leopard to default to the 64-bit kernel, only 64-bit device drivers would load. And seeing as Snow Leopard is the first version of Mac OS X to comprehend a 64-bit kernel, there'd live precious few of those on customers' systems on launch day.

    And so, by default, Snow Leopard boots with a 64-bit kernel only on Xserves from 2008 or later. I guess the assumption is that uncouth of the devices commonly attached to an Xserve will live supported by 64-bit drivers supplied by Apple in Snow Leopard itself.

    Perhaps surprisingly, not uncouth Macs with 64-bit processors are even able to boot into the 64-bit kernel. Though this may change in subsequent point releases of Snow Leopard, the table below lists uncouth the Macs that are either capable of or default to booting K64. (To find the "Model name" of your Mac, select "About This Mac" from the Apple menu, then click the "More info…" button and read the "Model Identifier" line in the window that appears.)

    Product Model name K64 status Early 2008 Mac Pro MacPro3,1 Capable Early 2008 Xserve Xserve2,1 Default MacBook Pro 15"/17" MacBookPro4,1 Capable iMac iMac8,1 Capable UniBody MacBook Pro 15" MacBookPro5,1 Capable UniBody MacBook Pro 17" MacBookPro5,2 Capable Mac Pro MacPro4,1 Capable iMac iMac9,1 Capable Early 2009 Xserve Xserve3,1 Default

    For uncouth K64-capable Macs, boot while holding down "6" and "4" keys simultaneously to select the 64-bit kernel. For a more permanent solution, use the nvram command to add arch=x86_64 to your boot-args string, or edit the file /Library/Preferences/SystemConfiguration/com.apple.Boot.plist and add arch=x86_64 to the Kernel Flags string:

    ... <key>Kernel</key> <string>mach_kernel</string> <key>Kernel Flags</key> <string>arch=x86_64</string> ...

    To switch back to the 32-bit kernel, hold down the "3" and "2" keys during boot, or use one of the techniques above, replacing "x86_64" with "i386".

    We've already discussed why, at least initially, you probably won't want to boot into K64. But as Snow Leopard adoption ramps up and 64-bit updates of existing kernel extensions become available, why might you actually want to use the 64-bit kernel?

    The first intuition has to conclude with RAM, and not in the pass you might think. Though Leopard uses a 32-bit kernel, Macs running Leopard can contain and use far more RAM than the 4 GB limit the "32-bit" qualifier might seem to imply. But as RAM sizes increase, there's another concern: address space depletion—not for applications, but for the kernel itself.

    As a 32-bit process, the kernel itself is limited to a 32-bit (i.e., 4GB) address space. That may not seem enjoy a problem; after all, should the kernel really exigency more than 4GB of remembrance to conclude its job? But bethink that piece of the kernel's job is to track and manage system memory. The kernel uses a 64-byte structure to track the status of each 4KB page of RAM used on the system.

    That's 64 bytes, not kilobytes. It hardly seems enjoy a lot. But now reckon a Mac in the not-too-distant future containing 96GB of RAM. (If this sounds ridiculous to you, judge of how ridiculous the 8GB of RAM in the Mac I'm typing on privilege now would Have sounded to you five years ago.) Tracking 96GB of RAM requires 1.5GB of kernel address space. Using more than a third of the kernel's address space just to track remembrance is a pretty uncomfortable situation.

    A 64-bit kernel, on the other hand, has a virtually unlimited kernel address space (16 exabytes). K64 is an inevitable necessity, given the rapidly increasing size of system memory. Though you may not exigency it today on the desktop, it's already common for servers to Have double-digit gigabytes of RAM installed.

    The other thing K64 has going for it is speed. The x86 instruction set architecture has had a bit of a tortured history. When designing the x86-64 64-bit extension of the x86 architecture, AMD took the opening to leave behind some of the ugliness of the past and comprehend more modern features: more registers, current addressing modes, non-stack-based floating point capabilities, etc. K64 reaps these benefits. Apple makes the following claims about its performance:

  • 250% faster system muster entry point
  • 70% faster user/kernel remembrance copy
  • Focused benchmarking would stand these out, I'm sure. But in daily use, you're unlikely to live able to attribute any particular performance boost to the kernel. judge of K64 as removing bottlenecks from the few (usually server-based) applications that actually conclude exercise these aspects of the kernel heavily.

    If it makes you feel better to know that your kernel is operating more efficiently, and that, were you to actually Have 96GB of RAM installed, you would not risk starving the kernel of address space, and if you don't Have any 32-bit drivers that you absolutely exigency to use, then by uncouth means, boot into the 64-bit kernel.

    For everyone else, my advice is to live joyous that K64 will live ready and waiting for you when you eventually conclude exigency it—and please conclude hearten uncouth the vendors that gain kernel extensions that you keeping about to add K64 uphold as soon as possible.

    Finally, this is worth repeating: please preserve in mind that you conclude not exigency to evade the 64-bit kernel in order to evade 64-bit applications or install more than 4GB of RAM in your Mac. Applications evade just fine in 64-bit mode on top of the 32-bit kernel, and even in earlier versions of Mac OS X it's been workable to install and seize edge of much more than 4GB of RAM.

    64-bit applications

    While Leopard may Have brought with it uphold for 64-bit GUI applications, it actually included very few of them. In fact, by my count, only two 64-bit GUI applications shipped with Leopard: Xcode (an optional install) and Chess. And though Leopard made it workable for third-party developers to yield 64-bit (albeit Leopard-only) GUI applications, very few have—sometimes due to ill-started realities, but most often because there's been no benign intuition to conclude so, abandoning users of Mac OS X 10.4 or earlier in the process.

    Apple is now pushing the 64-bit transition much harder. This starts with leading by example. Snow Leopard ships with four end-user GUI applications that are not 64-bit: iTunes, Grapher, Front Row, and DVD Player. Everything else is 64-bit. The Finder, the Dock, Mail, TextEdit, Safari, iChat, Address Book, Dashboard, succor Viewer, Installer, Terminal, Calculator—you title it, it's 64-bit.

    The second immense carrot (or stick, depending on how you watch at it) is the continued want of 32-bit uphold for current APIs and technologies. Leopard started the trend, leaving deprecated APIs behind and only porting the current ones to 64-bit. The improved Objective-C 2.0 runtime introduced in Leopard was besides 64-bit-only.

    Snow Leopard continues along similar lines. The Objective-C 2.1 runtime's non-fragile instance variables, exception model unified with C++, and faster vtable dispatch remain available only to 64-bit applications. But the most significant current 64-bit-only API is QuickTime X—significant enough to live addressed separately, so abide tuned.

    64-bits or bust

    All of this is Apple's not-so-subtle pass of telling developers that the time to Move to 64-bit is now, and that 64-bit should live the default for uncouth current applications, whether a developer thinks it's "needed" or not. In most cases, these current APIs Have no intrinsic connection to 64-bit. Apple has simply chosen to use them as additional forms of persuasion.

    Despite uncouth of the above, I'd quiet muster Snow Leopard merely the penultimate step in Mac OS X's journey to live 64-bit from top to bottom. I fully hope Mac OS X 10.7 to boot into the 64-bit kernel by default, to ship with 64-bit versions of uncouth applications, plug-ins, and kernel extensions, and to leave even more legacy and deprecated APIs to fade away in the land of 32-bit.

    QuickTime X

    Apple did something a bit odd in Leopard when it neglected to port the C-based QuickTime API to 64-bit. At the time, it didn't seem enjoy such a immense deal. Mac OS X's transition to 64-bit had already spanned many years and several major versions. One could imagine that it just wasn't yet QuickTime's whirl to Go 64-bit.

    As it turns out, my terse but pessimistic assessment of the situation at the time was accurate: QuickTime got the "Carbon treatment". enjoy Carbon, the venerable QuickTime API that they know and affection will not live making the transition to 64-bit—ever.

    To live clear, QuickTime the technology and QuickTime the brand will most definitely live coming to 64-bit. What's being left behind in 32-bit-only configuration is the C-based API introduced in 1991 and built upon for 18 years thereafter. Its replacement in the world of 64-bit in Snow Leopard is the aptly named QuickTime X.

    The "X" in QuickTime X, enjoy the one in in Mac OS X, is pronounced "ten." This is but the first of many eerie parallels. enjoy Mac OS X before it, QuickTime X:

  • aims to gain a cleanly fracture from its predecessor
  • is based on technology originally developed for another platform
  • includes transparent compatibility with its earlier incarnation
  • promises better performance and a more modern architecture
  • lacks many vital features in its initial release
  • Maximum available Mac CPU  quicken (MHz)Maximum available Mac CPU quicken (MHz)

    Let's seize these one at a time. First, why is a cleanly fracture needed? set aside simply, QuickTime is old—really old. The horribly blocky, postage-stamp-size video displayed by its initial release in 1991 was considered a technological tour de force.

    At the time, the fastest Macintosh money could buy contained a 25 MHz CPU. The ridiculous chart to the privilege is meant to hammer home this point. Forward-thinking design can only accept you so far. The shape of the world a technology is born into eventually, inevitably dictates its fate. This is especially steady for long-lived APIs enjoy QuickTime with a stalwart bent towards backward compatibility.

    As the first successful implementation of video on a personal computer, it's frankly incredible that the QuickTime API has lasted as long as it has. But the world has moved on. Just as Mac OS found itself mired in a ghetto of cooperative multitasking and unprotected memory, QuickTime limps into 2009 with antiquated notions of concurrency and subsystem layering baked into its design.

    When it came time to write the video-handling code for the iPhone, the latest version of QuickTime, QuickTime 7, simply wasn't up to the task. It had grown too bloated and inefficient during its life on the desktop, and it lacked benign uphold for the GPU-accelerated video playback necessary to ply modern video codecs on a handheld (even with a CPU sixteen times the clock quicken of any available in a Mac when QuickTime 1.0 was released). And so, Apple created a tight, modern, GPU-friendly video playback engine that could apt comfortably within the RAM and CPU constraints of the iPhone.

    Hmm. An aging desktop video API in exigency of a replacement. A fresh, current video library with benign performance even on (comparatively) anemic hardware. Apple connected the dots. But the trick is always in the transition. Happily, this is Apple's forte. QuickTime itself has already lived on three different CPU architectures and three entirely different operating systems.

    The switch to 64-bit is yet another (albeit less dramatic) inflection point, and Apple has chosen it to stamp the border between the traditional QuickTime 7 and the current QuickTime X. It's done this in Snow Leopard by limiting uncouth use of QuickTime by 64-bit applications to the QTKit Objective-C framework.

    QTKit's current world order

    QTKit is not new; it began its life in 2005 as a more native-feeling interface to QuickTime 7 for Cocoa applications. This extra layer of abstraction is the key to the QuickTime X transition. QTKit now hides within its object-oriented walls both QuickTime 7 and QuickTime X. Applications use QTKit as before, and behind the scenes QTKit will elect whether to use QuickTime 7 or QuickTime X to fulfill each request.

    If QuickTime X is so much better, why doesn't QTKit use it for everything? The retort is that QuickTime X, enjoy its Mac OS X namesake, has very limited capabilities in its initial release. While QuickTime X supports playback, capture, and exporting, it does not uphold general-purpose video editing. It besides supports only "modern" video formats—basically, anything that can live played by an iPod, iPhone, or Apple TV. As for other video codecs, well, you can forget about handling them with plug-ins because QuickTime X doesn't uphold those either.

    For every one of the cases where QuickTime X is not up to the job, QuickTime 7 will fill in. Cutting, copying, and pasting portions of a video? QuickTime 7. Extracting individual tracks from a movie? QuickTime 7. Playing any movie not natively supported by an existing Apple handheld device? QuickTime 7. Augmenting QuickTime's codec uphold using a plug-in of any kind? You guessed it: QuickTime 7.

    But wait a second. If QTKit is the only pass for a 64-bit application to use QuickTime, and QTKit multiplexes between QuickTime 7 and QuickTime X behind the scenes, and QuickTime 7 is 32-bit-only, and Mac OS X does not uphold "mixed mode" processes that can execute both 32-bit and 64-bit code, then how the heck does a 64-bit process conclude anything that requires the QuickTime 7 back-end?

    To find out, fire up the current 64-bit QuickTime Player application (which will live addressed separately later) and open a movie that requires QuickTime 7. Let's say, one that uses the Sorenson video codec. (Remember that? benign times.) positive enough, it plays just fine. But search for "QuickTime" in the Activity Monitor application and you'll behold this:

    Pretty sneaky, sis: 32-bit QTKitServer processPretty sneaky, sis: 32-bit QTKitServer process

    And the retort is revealed. When a 64-bit application using QTKit requires the services of the 32-bit-only QuickTime 7 back-end, QTKit spawns a separate 32-bit QTKitServer process to conclude the toil and communicate the results back to the originating 64-bit process. If you leave Activity Monitor open while using the current QuickTime Player application, you can watch the QTKitServer processes foster and Go as needed. This is uncouth handled transparently by the QTKit framework; the application itself exigency not live alert of these machinations.

    Yes, it's going to live a long, long time before QuickTime 7 disappears completely from Mac OS X (at least Apple was kindhearted enough not to muster it "QuickTime Classic"), but the path forward is clear. With each current release of Mac OS X, hope the capabilities of QuickTime X to expand, and the number of things that quiet require QuickTime 7 to decrease. In Mac OS X 10.7, for example, I imagine that QuickTime X will gain uphold for plug-ins. And surely by Mac OS X 10.8, QuickTime X will Have complete video editing support. uncouth this will live happening beneath the unifying facade of QTKit until, eventually, the QuickTime 7 back-end is no longer needed at all.

    Say what you mean

    In the meantime, perhaps surprisingly, many of the current limitations of QuickTime X actually highlight its unique advantages and inform the evolving QTKit API. Though there is no direct pass for a developer to request that QTKit use the QuickTime X back-end, there are several circuitous means to influence the decision. The key is the QTKit API, which relies heavily on the concept of intent.

    QuickTime versions 1 through 7 use a unique representation of uncouth media resources internally: a Movie object. This representation includes information about the individual tracks that gain up the movie, the sample tables for each track, and so on—all the information QuickTime needs to understand and exploit the media.

    This sounds Great until you realize that to conclude anything with a media resource in QuickTime requires the construction of this comprehensive Movie object. reckon playing an MP3 file with QuickTime, for example. QuickTime must create its internal Movie remonstrate representation of the MP3 file before it can originate playback. Unfortunately, the MP3 container format seldom contains comprehensive information about the structure of the audio. It's usually just a stream of packets. QuickTime must laboriously scan and parse the entire audio stream in order to complete the Movie object.

    QuickTime 7 and earlier versions gain this process less painful by doing the scanning and parsing incrementally in the background. You can behold this in many QuickTime-based player applications in the configuration of a progress bar overlaid on the movie controller. The image below shows a 63MB MP3 podcast loading in the Leopard version of QuickTime Player. The shaded portion of the movie timeline slowly fills the dotted area from left to right.

    QuickTime 7 doing more  toil than necessary

    QuickTime 7 doing more toil than necessary

    Though playback can originate almost immediately (provided you play from the beginning, that is) it's worthwhile to seize a step back and reckon what's going on here. QuickTime is creating a Movie remonstrate suitable for any operation that QuickTime can perform: editing, track extraction or addition, exporting, you title it. But what if uncouth I want to conclude is play the file?

    The wretchedness is, the QuickTime 7 API lacks a pass to express this kindhearted of intent. There is no pass to shriek to QuickTime 7, "Just open this file as quickly as workable so that I can play it. Don't bother reading every unique byte of the file from the disk and parsing it to determine its structure just in case I elect to edit or export the content. That is not my intent. Please, just open it for playback."

    The QTKit API in Snow Leopard provides exactly this capability. In fact, the only pass to live eligible for the QuickTime X back-end at uncouth is to explicitly express your intent not to conclude anything QuickTime X cannot handle. Furthermore, any attempt to achieve an operation that lies outside your previously expressed intent will cause QTKit to raise an exception.

    The intent mechanism is besides the pass that the current features of QuickTime X are exposed, such as the aptitude to asynchronously load great or distantly located (e.g., over a slack network link) movie files without blocking the UI running on the main thread of the application.

    Indeed, there are many reasons to conclude what it takes to accept on board the QuickTime X train. For the media formats it supports, QuickTime X is less taxing on the CPU during playback than QuickTime 7. (This is beyond the fact that QuickTime X does not fritter time preparing its internal representation of the movie for editing and export when playback is uncouth that's desired.) QuickTime X besides supports GPU-accelerated playback of H.264, but, in this initial release, only on Macs equipped with an NVIDIA 9400M GPU (i.e., some 2009 iMacs and several models of MacBooks from 2008 and 2009). Finally, QuickTime X includes comprehensive ColorSync uphold for video, which is long overdue.

    The X factor

    This is just the start of a long journey for QuickTime X, and seemingly not a very auspicious one, at that. A QuickTime engine with no editing support? No plug-ins? It seems ridiculous to release it at all. But this has been Apple's pass in recent years: steady, deliberate progress. Apple aims to ship no features before their time.

    As anxious as developers may live for a full-featured, 64-bit successor to the QuickTime 7 engine, Apple itself is sitting on top of one of the largest QuickTime-riddled (and Carbon-addled, to boot) code bases in the industry: Final nick Studio. Thus far, It remains stuck in 32-bit. To shriek that Apple is "highly motivated" to extend the capabilities of QuickTime X would live an understatement.

    Nevertheless, don't hope Apple to rush forward foolishly. Duplicating the functionality of a continually developed, 18-year-old API will not occur overnight. It will seize years, and it will live even longer before every vital Mac OS X application is updated to use QTKit exclusively. Transitions. Gotta affection 'em.

    File system API unification

    Mac OS X has historically supported many different ways of referring to files on disk from within an application. Plain-old paths (e.g., /Users/john/Documents/myfile) are supported at the lowest levels of the operating system. They're simple, predictable, but perhaps not such a Great sentiment to use as the only pass an application tracks files. reckon what happens if an application opens a file based on a path string, then the user moves that file somewhere else while it's quiet being edited. When the application is instructed to save the file, if it only has the file path to toil with, it will discontinuance up creating a current file in the traditional location, which is almost certainly not what the user wanted.

    Classic Mac OS had a more sophisticated internal representation of files that enabled it to track files independent of their actual locations on disk. This was done with the succor of the unique file ids supported by HFS/HFS+. The Mac OS X incarnation of this concept is the FSRef data type.

    Finally, in the modern age, URLs Have become the de facto representation for files that may live located somewhere other than the local machine. URLs can besides refer to local files, but in that case they Have uncouth the very disadvantages as file paths.

    This diversity of data types is reflected in Mac OS X's file system APIs. Some functions seize file path as arguments, some hope opaque references to files, and quiet others toil only with URLs. Programs that use these APIs often expend a lot of their time converting file references from one representation to another.

    The situation is similar when it comes to getting information about files. There are a huge number of file system metadata retrieval functions at uncouth levels of the operating system, and no unique one of them is comprehensive. To accept uncouth available information about a file on disk requires making several separate calls, each of which may hope a different character of file reference as an argument.

    Here's an illustration Apple provided at WWDC. Opening a unique file in the Leopard version of the Preview image viewer application results in:

  • Four conversions of an FSRef to a file path
  • Ten conversions of a file path to an FSRef
  • Twenty-five calls to getattrlist()
  • Eight calls to stat()/lstat()
  • Four calls to open()/close()
  • In Snow Leopard, Apple has created a new, unified, comprehensive set of file system APIs built around a unique data type: URLs. But these are URL "objects"—namely, the opaque data types NSURL and CFURL, with a toll-free bridge between them—that Have been imbued with uncouth the desirable attributes of an FSRef.

    Apple settled on these data types because their opaque nature allowed this kindhearted of enhancement, and because there are so many existing APIs that use them. URLs are besides the most future-proof of uncouth the choices, with the scheme portion providing nearly unlimited flexibility for current data types and access mechanisms. The current file system APIs built around these opaque URL types uphold caching and metadata prefetching for a further performance boost.

    There's besides a current on-disk representation called a Bookmark (not to live confused with a browser bookmark) which is enjoy a more network-savvy replacement for classic Mac OS aliases. Bookmarks are the most robust pass to create a reference to a file from within another file. It's besides workable to attach whimsical metadata to each Bookmark. For example, if an application wants to preserve a persistent list of "favorite" files plus some application-specific information about them, and it wants to live resilient to any movement of these files behind its back, Bookmarks are the best appliance for the job.

    I mention uncouth of this not because I hope file system APIs to live uncouth that touching to people without my particular fascination with this piece of the operating system, but because, enjoy Core Text before it, it's an indication of exactly how young Mac OS X really is as a platform. Even after seven major releases, Mac OS X is quiet struggling to Move out from the shadow of its three ancestors: NeXTSTEP, classic Mac OS, and BSD Unix. Or perhaps it just goes to pomp how ruthlessly Apple's core OS team is driven to replace traditional and crusty APIs and data types with new, more modern versions.

    It will live a long time before the benefits of these changes trickle down (or is it up?) to end-users in the configuration of Mac applications that are written or modified to use these current APIs. Most well-written Mac applications already exhibit most of the desirable behavior. For example, the TextEdit application in Leopard will correctly detect when a file it's working on has moved.

    TextEdit: a   benign Mac OS X citizenTextEdit: a benign Mac OS X citizen

    Of course, the key modifier here is "well-written." Simplifying the file system APIs means that more developers will live willing to expend the effort—now greatly reduced—to provide such user-friendly behaviors. The accompanying performance boost is just icing on the cake, and one more intuition that developers might elect to alter their existing, working application to use these current APIs.

    Doing more with more

    Moore's Law is widely cited in technology circles—and besides widely misunderstood. It's most often used as shorthand for "computers double in quicken every year or so," but that's not what Gordon Moore wrote at all. His 1965 article in Electronics magazine touched on many topics in the semiconductor industry, but if it had to live summed up in a unique "law", it would be, roughly, that the number of transistors that apt onto a square inch of silicon doubles every 12 months.

    Moore later revised that to two years, but the time term is not what people accept wrong. The problem is confusing a doubling of transistor density with a doubling of "computer speed." (Even more problematic is declaring a "law" based on a unique paper from 1965, but we'll set aside that aside for now. For a more thorough discussion of Moore's Law, please read this classic article by Jon Stokes.)

    For decades, each expand in transistor density was, in fact, accompanied by a comparable expand in computing quicken thanks to ever-rising clock speeds and the dawn of superscalar execution. This worked great—existing code ran faster on each current CPU—until the grim realities of power density set aside an discontinuance to the fun.

    Moore's Law continues, at least for now, but their aptitude to gain code evade faster with each current expand in transistor density has slowed considerably. The free lunch is over. CPU clock speeds Have stagnated for years, many times actually going backwards. (The latest top-of-the-line 2009 Mac Pro contains a 2.93 GHz CPU, whereas the 2008 model could live equipped with a 3.2 GHz CPU.) Adding execution units to a CPU has besides long since reached the point of diminishing returns, given the limits of instruction-level parallelism in common application code.

    And yet we've quiet got uncouth these current transistors raining down on us, more every year. The challenge is to find current ways to use them to actually gain computers faster.

    Thus far, the semiconductor industry's retort has been to give us more of what they already have. Where once a CPU contained a unique ratiocinative processing unit, now CPUs in even the lowliest desktop computers contain two processor cores, with high-end models sporting two chips with eight ratiocinative cores each. Granted, the cores themselves are besides getting faster, usually by doing more at the very clock quicken as their predecessors, but that's not happening at nearly the rate that the cores are multiplying.

    Unfortunately, generally speaking, a dual-core CPU will not evade your application twice as enjoy a gleam as a single-core CPU. In fact, your application probably won't evade any faster at uncouth unless it was written to seize edge of more than just a unique ratiocinative CPU. Presented with a glut of transistors, chipmakers Have turned around and provided more computing resources than programmers know what to conclude with, transferring much of the responsibility for making computers faster to the software guys.

    We're with the operating system and we're here to help

    It's into this environment that Snow Leopard is born. If there's one responsibility (aside from security) that an operating system vendor should feel in the year 2009, it's finding a pass for applications—and the OS itself—to utilize the ever-growing wealth of computing resources at their disposal. If I had to pick unique technological "theme" for Snow Leopard, this would live it: helping developers utilize uncouth this newfound silicon; helping them conclude more with more.

    To that end, Snow Leopard includes two significant current APIs backed by several smaller, but equally vital infrastructure improvements. We'll start at the bottom with, believe it or not, the compiler.

    LLVM and Clang

    Apple made a strategic investment in the LLVM open source project several years ago. I covered the fundamentals of LLVM in my Leopard review. (If you're not up to speed, please entrap up on the topic before continuing.) In it, I described how Leopard used LLVM to provide dramatically more efficient JIT-compiled software implementations of OpenGL functions. I ended with the following admonition:

    Don't live misled by its humble use in Leopard; Apple has majestic plans for LLVM. How grand? How about swapping out the guts of the gcc compiler Mac OS X uses now and replacing them with the LLVM equivalents? That project is well underway. Not ambitious enough? How about ditching gcc entirely, replacing it with a completely current LLVM-based (but gcc-compatible) compiler system? That project is called Clang, and it's already yielded some impressive performance results.

    With the introduction of Snow Leopard, it's official: Clang and LLVM are the Apple compiler strategy going forward. LLVM even has a snazzy current logo, a not-so-subtle homage to a well-known compiler design textbook:

    LLVM! Clang! Rawr!

    LLVM! Clang! Rawr!

    Apple now offers a total of four compilers for Mac OS X: GCC 4.0, GCC 4.2, LLVM-GCC 4.2 (the GCC 4.2 front-end combined with an LLVM back-end), and Clang, in order of increasing LLVM-ness. Here's a diagram:

    Mac OS X compilers

    Mac OS X compilers

    All of these compilers are binary-compatible on Mac OS X, which means you can, for example, build a library with one compiler and link it into an executable built with another. They're besides uncouth command-line and source-compatible—in theory, anyway. Clang does not yet uphold some of the more esoteric features of GCC. Clang besides only supports C, Objective-C, and a itsy-bitsy bit of C++ (Clang(uage), accept it?) whereas GCC supports many more. Apple is committed to complete C++ uphold for Clang, and hopes to toil out the remaining GCC incompatibilities during Snow Leopard's lifetime.

    Clang brings with it the two headline attributes you hope in a hot, current compiler: shorter compile times and faster executables. In Apple's testing with its own applications such as iCal, Address Book, and Xcode itself, plus third-party applications enjoy Adium and Growl, Clang compiles nearly three times faster than GCC 4.2. As for the quicken of the finished product, the LLVM back-end, whether used in Clang or in LLVM-GCC, produces executables that are 5-25% faster than those generated by GCC 4.2.

    Clang is besides more developer-friendly than its GCC predecessors. I concede that this topic doesn't Have much to conclude with taking edge of multiple CPU cores and so on, but it's positive to live the first thing that a developer actually notices when using Clang. Indulge me.

    For starters, Clang is embeddable, so Xcode can use the very compiler infrastructure for interactive features within the IDE (symbol look-up, code completion, etc.) as it uses to compile the final executable. Clang besides creates and preserves more extensive metadata while compiling, resulting in much better oversight reporting. For example, when GCC tells you this:

    GCC  oversight message for an unknown type

    It's not exactly pellucid what the problem is, especially if you're current to C programming. Yes, uncouth you hotshots already know what the problem is (especially if you saw this illustration at WWDC), but I judge everyone can conform that this error, generated by Clang, is a lot more helpful:

    Clang  oversight message for an unknown type

    Maybe a novice quiet wouldn't know what to do, but at least it's pellucid where the problem lies. Figuring out why the compiler doesn't know about NSString is a much more focused task than can live derived from GCC's cryptic error.

    Even when the message is clear, the context may not be. seize this oversight from GCC:

    GCC  oversight message for  inferior operands

    Sure, but there are four "+" operators on that unique line. Which one has the problematic operands? Thanks to its more extensive metadata, Clang can pinpoint the problem:

    Clang  oversight message for  inferior operands

    Sometimes the oversight is perfectly clear, but it just seems a bit off, enjoy this situation where jumping to the oversight as reported by GCC puts you on the line below where you actually want to add the missing semicolon:

    GCC  oversight message for missing semicolon

    The itsy-bitsy things count, you know? Clang goes that extra mile:

    Clang  oversight message for missing semicolon

    Believe it or not, stuff enjoy this means a lot to developers. And then there are the not-so-little things that weigh in even more, enjoy the LLVM-powered static analyzer. The image below shows how the static analyzer displays its discovery of a workable bug.

    OH HAI I found UR BUGOH HAI I found UR BUG

    Aside from the whimsy of the itsy-bitsy arrows (which, admit it, are adorable), the actual bug it's highlighting is something that every programmer can imagine creating (say, through some hasty editing). The static analyzer has determined that there's at least one path through this set of nested conditionals that leaves the myName variable uninitialized, thus making the attempt to ship the mutableCopy message in the final line potentially dangerous.

    I'm positive Apple is going hog-wild running the static analyzer on uncouth of its applications and the operating system itself. The prospect of an automated pass to determine bugs that may Have existed for years in the depths of a huge codebase is almost pornographic to developers—platform owners in particular. To the degree that Mac OS X 10.6.0 is more bug-free than the previous 10.x.0 releases, LLVM surely deserves some significant piece of the credit.

    Master of the house

    By committing to a Clang/LLVM-powered future, Apple has finally taken complete control of its evolution platform. The CodeWarrior experience apparently convinced Apple that it's unwise to reliance on a third party for its platform's evolution tools. Though it's taken many years, I judge even the most diehard Metrowerks fan would Have to conform that Xcode in Snow Leopard is now a pretty damn benign IDE.

    After years of struggling with the disconnect between the goals of the GCC project and its own compiler needs, Apple has finally nick the apron strings. OK, granted, GCC 4.2 is quiet the default compiler in Snow Leopard, but this is a transitional phase. Clang is the recommended compiler, and the focus of uncouth of Apple's future efforts.

    I know what you're thinking. This is swell and all, but how are these compilers helping developers better leverage the expanding swarm of transistors at their disposal? As you'll behold in the following sections, LLVM's scaly, metallic head pops up in a few key places.

    Blocks

    In Snow Leopard, Apple has introduced a C language extension called "blocks." Blocks add closures and anonymous functions to C and the C-derived languages C++, Objective-C, and Objective C++.

    These features Have been available in dynamic programming languages such as Lisp, Smalltalk, Perl, Python, Ruby, and even the unassuming JavaScript for a long time (decades, in the case of Lisp—a fact gladly offered by its practitioners). While dynamic-language programmers seize closures and anonymous functions for granted, those who toil with more traditional, statically compiled languages such as C and its derivatives may find them quite exotic. As for non-programmers, they likely Have no interest in this topic at all. But I'm going to attempt an explanation nonetheless, as blocks configuration the foundation of some other touching technologies to live discussed later.

    Perhaps the simplest pass to complicated blocks is that they gain functions another configuration of data. C-derived languages already Have office pointers, which can live passed around enjoy data, but these can only point to functions created at compile time. The only pass to influence the deportment of such a office is by passing different arguments to the office or by setting global variables which are then accessed from within the function. Both of these approaches Have immense disadvantages

    Passing arguments becomes cumbersome as their number and complexity grows. Also, it may live that you Have limited control over the arguments that will live passed to your function, as is often the case with callbacks. To compensate, you may Have to bundle up uncouth of your touching condition into a context remonstrate of some kind. But when, how, and by whom that context data will live disposed of can live difficult to pin down. Often, a second callback is required for this. It's uncouth quite a pain.

    As for the use of global variables, in addition to being a well-known anti-pattern, it's besides not thread-safe. To gain it so requires locks or some other configuration of mutual exclusion to forestall multiple invocations of the very office from stepping on each other's toes. And if there's anything worse than navigating a sea of callback-based APIs, it's manually dealing with thread safety issues.

    Blocks bypass uncouth of these problems by allowing functional blobs of code—blocks—to live defined at runtime. It's easiest to understand with an example. I'm going to start by using JavaScript, which has a bit friendlier syntax, but the concepts are the same.

    b = get_number_from_user(); multiplier = function(a) { revert a * b };

    Here I've created a office named multiplier that takes a unique argument, a, and multiplies it by a second value, b, that's provided by the user at runtime. If the user supplied the number 2, then a muster to multiplier(5) would revert the value 10.

    b = get_number_from_user(); // assume it's 2 multiplier = function(a) { revert a * b }; r = multiplier(5); // 5 * 2 = 10

    Here's the illustration above done with blocks in C.

    b = get_number_from_user(); // assume it's 2 multiplier = ^ int (int a) { revert a * b; }; r = multiplier(5); // 5 * 2 = 10

    By comparing the JavaScript code to the C version, I hope you can behold how it works. In the C example, that itsy-bitsy caret ^ is the key to the syntax for blocks. It's kindhearted of ugly, but it's very C-like in that it parallels the existing C syntax for office pointers, with ^ in site of *, as this illustration illustrates:

    /* A office that takes a unique integer controversy and returns a pointer to a office that takes two integer arguments and returns a floating-point number. */ float (*func2(int a))(int, int); /* A office that takes a unique integer controversy and returns a shroud that takes two integer arguments and returns a floating-point number. */ float (^func1(int a))(int, int);

    You'll just Have to reliance me when I disclose you that this syntax actually makes sense to seasoned C programmers.

    Now then, does this weigh in that C is suddenly a dynamic, high-level language enjoy JavaScript or Lisp? Hardly. The existing distinction between the stack and the heap, the rules governing automatic and static variables, and so on are uncouth quiet in complete effect. Plus, now there's a whole current set of rules for how blocks interact with each of these things. There's even a current __block storage character attribute to further control the scope and lifetime of values used in blocks.

    All of that said, blocks are quiet a huge win in C. Thanks to blocks, the friendlier APIs long enjoyed by dynamic languages are now workable in C-derived languages. For example, suppose you want to apply some operation to every line in a file. To conclude so in a low-level language enjoy C requires some amount of boilerplate code to open and read from the file, ply any errors, read each line into a buffer, and cleanly up at the end.

    FILE *fp = fopen(filename, "r"); if (fp == NULL) { perror("Unable to open file"); } else { char line[MAX_LINE]; while (fgets(line, MAX_LINE, fp)) { work; work; work; } fclose(fp); }

    The piece in bold is an abstract representation of what you're planning to conclude to each line of the file. The ease is the literal boilerplate code. If you find yourself having to apply varying operations to every line of many different files, this boilerplate code gets tedious.

    What you'd enjoy to live able to conclude is factor it out into a office that you can call. But then you're faced with the problem of how to express the operation you'd enjoy to achieve on each line of the file. In the middle of each shroud of boilerplate may live many lines of code expressing the operation to live applied. This code may reference or modify local variables which are affected by the runtime deportment of the program, so traditional office pointers won't work. What to do?

    Thanks to blocks, you can define a office that takes a filename and a shroud as arguments. This gets uncouth the uninteresting code out of your face.

    foreach_line(filename, ^ (char *line) { work; work; work; });

    What's left is a much clearer expression of your intent, with less surrounding noise. The controversy after filename is a literal shroud that takes a line of text as an argument.

    Even when the volume of boilerplate is small, the simplicity and clarity premium is quiet worthwhile. reckon the simplest workable loop that executes a fixed number of times. In C-based languages, even that basic construct offers a surprising number of opportunities for bugs. Let's do_something() 10 times:

    for (int i = 0; i <= 10; i++) { do_something(); }

    Oops, I've got a itsy-bitsy bug there, don't I? It happens to the best of us. But why should this code live more complicated than the sentence describing it. conclude something 10 times! I never want to screw that up again. Blocks can help. If they just invest a itsy-bitsy application up front to define a helper function:

    typedef void (^work_t)(void); void repeat(int n, work_t block) { for (int i = 0; i < n; ++i) block(); }

    We can extradite the bug for good. Now, repeating any whimsical shroud of code a specific number of times is uncouth but idiot-proof:

    repeat(10, ^{ do_something() }); repeat(20, ^{ do_other_thing() });

    And remember, the shroud controversy to repeat() can contain exactly the very kindhearted of code, literally copied and pasted, that would Have appeared within a traditional for loop.

    All these possibilities and more Have been well explored by dynamic languages: map, reduce, collect, etc. Welcome, C programmers, to a higher order.

    Apple has taken these lessons to heart, adding over 100 current APIs that use blocks in Snow Leopard. Many of these APIs would not live workable at uncouth without blocks, and uncouth of them are more elegant and concise than they would live otherwise.

    It's Apple objective to submit blocks as an official extension to one or more of the C-based languages, though it's not yet pellucid which standards bodies are receptive to the proposal. For now, blocks are supported by uncouth four of Apple's compilers in Mac OS X.

    Concurrency in the actual world: a prelude

    The struggle to gain efficient use of a great number of independent computing devices is not new. For decades, the domain of high-performance computing has tackled this problem. The challenges faced by people writing software for supercomputers many years ago Have now trickled down to desktop and even mobile computing platforms.

    In the PC industry, some people saw this coming earlier than others. Almost 20 years ago, live Inc. was formed around the sentiment of creating a PC platform unconstrained by legacy limitations and entirely prepared for the coming abundance of independent computing units on the desktop. To that end, live created the BeBox, a dual-CPU desktop computer, and BeOS, a brand-new operating system.

    The signature entrap phrase for BeOS was "pervasive multithreading." The BeBox and other machines running BeOS leveraged every ounce of the diminutive (by today's standards, anyway) computing resources at their disposal. The demos were impressive. A dual 66 MHz machine (don't gain me pomp another graph) could play multiple videos simultaneously while besides playing several audio tracks from a CD—some backwards— and uncouth the while, the user interface remained completely responsive.

    Let me disclose you, having lived through this term myself, the experience was mind-blowing at the time. BeOS created instant converts out of hundreds of technology enthusiasts, many of whom maintain that today's desktop computing experience quiet doesn't match the responsiveness of BeOS. This is certainly steady emotionally, if not necessarily literally.

    After nearly purchasing live in the late 1990s, Apple bought NeXT instead, and the ease is history. But had Apple gone with objective live instead, Mac developers might Have had a rugged road ahead. While uncouth that pervasive multithreading made for impressive technology demos and a Great user experience, it could live extremely demanding on the programmer. BeOS was uncouth about threads, going so far as to maintain a separate thread for each window. Whether you liked it or not, your BeOS program was going to live multithreaded.

    Parallel programming is notoriously hard, with the manual management of POSIX-style threads representing the abysmal discontinuance of that pool. The best programmers in the world are hard-pressed to create great multithreaded programs in low-level languages enjoy C or C++ without finding themselves impaled on the spikes of deadlock, race conditions, and other perils inherent in the use of in multiple simultaneous threads of execution that partake the very remembrance space. Extremely watchful application of locking primitives is required to avoid performance-robbing levels of contention for shared data—and the bugs, oh the bugs! The term "Heisenbug" may as well Have been invented for multithreaded programming.

    Nineteen years after live tilted at the windmill of the widening swath of silicon in desktop PCs, the challenge has only grown. Those transistors are out there, man—more than ever before. Single-threaded programs on today's high-end desktop Macs, even when using "100%" CPU, extend but a unique glowing tower in a sea of sixteen otherwise vacuous lanes on a CPU monitor window.

    A wide-open  modest of transistorsA wide-open modest of transistors

    And woe live unto the user if that pegged CPU core is running the main thread of a GUI application on Mac OS X. A CPU-saturated main thread means no current user inputs are being pulled off the event queue by the application. A few seconds of that and an traditional friend makes its appearance: the spinning beach ball of death.

    Nooooooooo!!!

    Nooooooooo!!! Image from The Iconfactory

    This is the enemy: hardware with more computing resources than programmers know what to conclude with, most of it completely idle, and uncouth the while the user is utterly blocked in his attempts to use the current application. What's Snow Leopard's answer? Read on…

    Grand Central Dispatch Apple's GCD branding: <a href="http://en.wikipedia.org/wiki/Foamer">Railfan</a> <a href="http://en.wikipedia.org/wiki/Fan_service">service</a>Apple's GCD branding: Railfan service

    Snow Leopard's retort to the concurrency conundrum is called majestic Central Dispatch (GCD). As with QuickTime X, the title is extremely apt, though this is not entirely pellucid until you understand the technology.

    The first thing to know about GCD is that it's not a current Cocoa framework or similar special-purpose frill off to the side. It's a modest C library baked into the lowest levels of Mac OS X. (It's in libSystem, which incorporates libc and the other code that sits at the very bottom of userspace.)

    There's no exigency to link in a current library to use GCD in your program. Just #include <dispatch/dispatch.h> and you're off to the races. The fact that GCD is a C library means that it can live used from uncouth of the C-derived languages supported on Mac OS X: Objective-C, C++, and Objective-C++.

    Queues and threads

    GCD is built on a few simple entities. Let's start with queues. A queue in GCD is just what it sounds like. Tasks are enqueued, and then dequeued in FIFO order. (That's "First In, First Out," just enjoy the checkout line at the supermarket, for those who don't know and don't want to follow the link.) Dequeuing the task means handing it off to a thread where it will execute and conclude its actual work.

    Though GCD queues will hand tasks off to threads in FIFO order, several tasks from the very queue may live running in parallel at any given time. This animation demonstrates.

    A majestic Central Dispatch queue in action

    You'll notice that task B completed before task A. Though dequeuing is FIFO, task completion is not. besides note that even though there were three tasks enqueued, only two threads were used. This is an vital feature of GCD which we'll dispute shortly.

    But first, let's watch at the other kindhearted of queue. A serial queue works just enjoy a timehonored queue, except that it only executes one task at a time. That means task completion in a serial queue is besides FIFO. Serial queues can live created explicitly, just enjoy timehonored queues, but each application besides has an implicit "main queue" which is a serial queue that runs on the main thread.

    The animation above shows threads appearing as toil needs to live done, and disappearing as they're no longer needed. Where conclude these threads foster from and where conclude they Go when they're done? GCD maintains a global pool of threads which it hands out to queues as they're needed. When a queue has no more pending tasks to evade on a thread, the thread goes back into the pool.

    This is an extremely vital aspect of GCD's design. Perhaps surprisingly, one of the most difficult parts of extracting maximum performance using traditional, manually managed threads is figuring out exactly how many threads to create. Too few, and you risk leaving hardware idle. Too many, and you start to expend a significant amount of time simply shuffling threads in and out of the available processor cores.

    Let's shriek a program has a problem that can live split into eight separate, independent units of work. If this program then creates four threads on an eight-core machine, is this an illustration of creating too many or too few threads? Trick question! The retort is that it depends on what else is happening on the system.

    If six of the eight cores are totally saturated doing some other work, then creating four threads will just require the OS to fritter time rotating those four threads through the two available cores. But wait, what if the process that was saturating those six cores finishes? Now there are eight available cores but only four threads, leaving half the cores idle.

    With the exception of programs that can reasonably hope to Have the entire machine to themselves when they run, there's no pass for a programmer to know ahead of time exactly how many threads he should create. Of the available cores on a particular machine, how many are in use? If more become available, how will my program know?

    The bottom line is that the optimal number of threads to set aside in flight at any given time is best determined by a single, globally alert entity. In Snow Leopard, that entity is GCD. It will preserve zero threads in its pool if there are no queues that Have tasks to run. As tasks are dequeued, GCD will create and dole out threads in a pass that optimizes the use of the available hardware. GCD knows how many cores the system has, and it knows how many threads are currently executing tasks. When a queue no longer needs a thread, it's returned to the pool where GCD can hand it out to another queue that has a task ready to live dequeued.

    There are further optimizations inherent in this scheme. In Mac OS X, threads are relatively heavyweight. Each thread maintains its own set of register values, stack pointer, and program counter, plus kernel data structures tracking its security credentials, scheduling priority, set of pending signals and signal masks, etc. It uncouth adds up to over 512 KB of overhead per thread. Create a thousand threads and you've just burned about a half a gigabyte of remembrance and kernel resources on overhead alone, before even considering the actual data within each thread.

    Compare a thread's 512 KB of baggage with GCD queues which Have a mere 256 bytes of overhead. Queues are very lightweight, and developers are encouraged to create as many of them as they need—thousands, even. In the earlier animation, when the queue was given two threads to process its three tasks, it executed two tasks on one of the threads. Not only are threads heavyweight in terms of remembrance overhead, they're besides relatively costly to create. Creating a current thread for each task would live the worst workable scenario. Every time GCD can use a thread to execute more than one task, it's a win for overall system efficiency.

    Remember the problem of the programmer trying to device out how many threads to create? Using GCD, he doesn't Have to worry about that at all. Instead, he can concentrate entirely on the optimal concurrency of his algorithm in the abstract. If the best-case scenario for his problem would use 500 concurrent tasks, then he can Go ahead and create 500 GCD queues and dole his toil among them. GCD will device out how many actual threads to create to conclude the work. Furthermore it will adjust the number of threads dynamically as the conditions on the system change.

    But perhaps most importantly, as current hardware is released with more and more CPU cores, the programmer does not exigency to change his application at all. Thanks to GCD, it will transparently seize edge of any and uncouth available computing resources, up to—but not past!—the optimal amount of concurrency as originally defined by the programmer when he chose how many queues to create.

    But wait, there's more! GCD queues can actually live arranged in arbitrarily tangled directed acyclic graphs. (Actually, they can live cyclic too, but then the deportment is undefined. Don't conclude that.) Queue hierarchies can live used to funnel tasks from disparate subsystems into a narrower set of centrally controlled queues, or to compel a set of timehonored queues to delegate to a serial queue, effectively serializing them uncouth indirectly.

    There are besides several levels of priority for queues, dictating how often and with what urgency threads are distributed to them from the pool. Queues can live suspended, resumed, and cancelled. Queues can besides live grouped, allowing uncouth tasks distributed to the group to live tracked and accounted for as a unit.

    Overall, GCD's use of queues and threads forms a simple, elegant, but besides extremely pragmatic architecture.

    Asynchronicity

    Okay, so GCD is a Great pass to gain efficient use of the available hardware. But is it really any better than BeOS's approach to multithreading? We've already seen a few ways that GCD avoids the pitfalls of BeOS (e.g., the reuse of threads and the maintenance of a global pool of threads that's correctly sized for the available hardware). But what about the problem of overwhelming the programmer by requiring threads in places where they complicate, rather than enhance the application?

    GCD embodies a philosophy that is at the contradictory discontinuance of the spectrum from BeOS's "pervasive multithreading" design. Rather than achieving responsiveness by getting every workable component of an application running concurrently on its own thread (and paying a cumbersome cost in terms of tangled data sharing and locking concerns), GCD encourages a much more limited, hierarchical approach: a main application thread where uncouth the user events are processed and the interface is updated, and worker threads doing specific jobs as needed.

    In other words, GCD doesn't require developers to judge about how best to split the toil of their application into multiple concurrent threads (though when they're ready to conclude that, GCD will live willing and able to help). At its most basic level, GCD aims to hearten developers to Move from thinking synchronously to thinking asynchronous. Something enjoy this: "Write your application as usual, but if there's any piece of its operation that can reasonably live expected to seize more than a few seconds to complete, then for the affection of Zarzycki, accept it off the main thread!"

    That's it; no more, no less. Beach ball banishment is the cornerstone of user interface responsiveness. In some respects, everything else is gravy. But most developers know this intuitively, so why conclude they quiet behold the beach ball in Mac OS X applications? Why don't uncouth applications already execute uncouth of their potentially long-running tasks on background threads?

    A few reasons Have been mentioned already (e.g., the vicissitude of knowing how many threads to create) but the immense one is much more pragmatic. Spinning off a thread and collecting its result has always been a bit of a pain. It's not so much that it's technically difficult, it's just that it's such an express fracture from coding the actual toil of your application to coding uncouth this task-management plumbing. And so, especially in borderline cases, enjoy an operation that may seize 3 to 5 seconds, developers just conclude it synchronously and Move onto the next thing.

    Unfortunately, there's a surprising number of very common things that an application can conclude that execute quickly most of the time, but Have the potential to seize much longer than a few seconds when something goes wrong. Anything that touches the file system may stall at the lowest levels of the OS (e.g., within blocking read() and write() calls) and live matter to a very long (or at least an "unexamined-by-the-application-developer") timeout. The very goes for title lookups (e.g., DNS or LDAP), which almost always execute instantly, but entrap many applications completely off-guard when they start taking their sweet time to revert a result. Thus, even the most meticulously constructed Mac OS X applications can discontinuance up throwing the beach ball in their physiognomy from time to time.

    With GCD, Apple is saying it doesn't Have to live this way. For example, suppose a document-based application has a button that, when clicked, will analyze the current document and pomp some touching statistics about it. In the common case, this analysis should execute in under a second, so the following code is used to connect the button with an action:

    - (IBAction)analyzeDocument:(NSButton *)sender { NSDictionary *stats = [myDoc analyze]; [myModel setDict:stats]; [myStatsView setNeedsDisplay:YES]; [stats release]; }

    The first line of the office cadaver analyzes the document, the second line updates the application's internal state, and the third line tells the application that the statistics view needs to live updated to reflect this current state. It uncouth follows a very common pattern, and it works Great as long as null of these steps—which are uncouth running on the main thread, remember—takes too long. Because after the user presses the button, the main thread of the application needs to ply that user input as enjoy a gleam as workable so it can accept back to the main event loop to process the next user action.

    The code above works Great until a user opens a very great or very tangled document. Suddenly, the "analyze" step doesn't seize one or two seconds, but 15 or 30 seconds instead. Hello, beach ball. And still, the developer is likely to hem and haw: "This is really an exceptional situation. Most of my users will never open such a great file. And anyway, I really don't want to start reading documentation about threads and adding uncouth that extra code to this simple, four-line function. The plumbing would dwarf the code that does the actual work!"

    Well, what if I told you that you could Move the document analysis to the background by adding just two lines of code (okay, and two lines of closing braces), uncouth located within the existing function? No application-global objects, no thread management, no callbacks, no controversy marshalling, no context objects, not even any additional variables. Behold, majestic Central Dispatch:

    - (IBAction)analyzeDocument:(NSButton *)sender { dispatch_async(dispatch_get_global_queue(0, 0), ^{ NSDictionary *stats = [myDoc analyze]; dispatch_async(dispatch_get_main_queue(), ^{ [myModel setDict:stats]; [myStatsView setNeedsDisplay:YES]; [stats release]; }); }); }

    There's a hell of a lot of packed into those two lines of code. uncouth of the functions in GCD originate with dispatch_, and you can behold four such calls in the blue lines of code above. The key to the minimal invasiveness of this code is revealed in the second controversy to the two dispatch_async() calls. Thus far, I've been discussing "units of work" without specifying how, exactly, GCD models such a thing. The answer, now revealed, should seem obvious in retrospect: blocks! The aptitude of blocks to capture the surrounding context is what allows these GCD calls to live dropped privilege into some existing code without requiring any additional setup or re-factoring or other contortions in service of the API.

    But the best piece of this code is how it deals with the problem of detecting when the background task completes and then showing the result. In the synchronous code, the analyze pass muster and the code to update the application pomp simply appear in the desired sequence within the function. In the asynchronous code, miraculously, this is quiet the case. Here's how it works.

    The outer dispatch_async() muster puts a task on a global concurrent GCD queue. That task, represented by the shroud passed as the second argument, contains the potentially time-consuming analyze pass call, plus another muster to dispatch_async() that puts a task onto the main queue—a serial queue that runs on the main thread, remember—to update the application's user interface.

    User interface updates must uncouth live done from the main thread in a Cocoa application, so the code in the inner shroud could not live executed anywhere else. But rather than having the background thread ship some kindhearted of special-purpose notification back to the main thread when the analyze pass muster completes (and then adding some code to the application to detect and ply this notification), the toil that needs to live done on the main thread to update the pomp is encapsulated in yet another shroud within the larger one. When the analyze muster is done, the inner shroud is set aside onto the main queue where it will (eventually) evade on the main thread and conclude its toil of updating the display.

    Simple, elegant, and effective. And for developers, no more excuses.

    Believe it or not, it's just as simple to seize a serial implementation of a progression of independent operations and parallelize it. The code below does toil on count elements of data, one after the other, and then summarizes the results once uncouth the elements Have been processed.

    for (i = 0; i < count; i++) { results[i] = do_work(data, i); } total = summarize(results, count);

    Now here's the parallel version which puts a separate task for each ingredient onto a global concurrent queue. (Again, it's up to GCD to elect how many threads to actually use to execute the tasks.)

    dispatch_apply(count, dispatch_get_global_queue(0, 0), ^(size_t i) { results[i] = do_work(data, i); }); total = summarize(results, count);

    And there you Have it: a for loop replaced with a concurrency-enabled equivalent with one line of code. No preparation, no additional variables, no impossible decisions about the optimal number of threads, no extra toil required to wait for uncouth the independent tests to complete. (The dispatch_apply() muster will not revert until uncouth the tasks it has dispatched Have completed.) Stunning.

    Grand Central Awesome

    Of uncouth the APIs added in Snow Leopard, majestic Central Dispatch has the most far-reaching implications for the future of Mac OS X. Never before has it been so simple to conclude toil asynchronously and to spread workloads across many CPUs.

    When I first heard about majestic Central Dispatch, I was extremely skeptical. The greatest minds in computer science Have been working for decades on the problem of how best to extract parallelism from computing workloads. Now here was Apple apparently promising to decipher this problem. Ridiculous.

    But majestic Central Dispatch doesn't actually address this issue at all. It offers no succor whatsoever in deciding how to split your toil up into independently executable tasks—that is, deciding what pieces can or should live executed asynchronously or in parallel. That's quiet entirely up to the developer (and quiet a tough problem). What GCD does instead is much more pragmatic. Once a developer has identified something that can live split off into a separate task, GCD makes it as simple and non-invasive as workable to actually conclude so.

    The use of FIFO queues, and especially the actuality of serialized queues, seems counter to the spirit of ubiquitous concurrency. But we've seen where the Platonic ideal of multithreading leads, and it's not a pleasant site for developers.

    One of Apple's slogans for majestic Central Dispatch is "islands of serialization in a sea of concurrency." That does a Great job of capturing the practical reality of adding more concurrency to run-of-the-mill desktop applications. Those islands are what sequester developers from the thorny problems of simultaneous data access, deadlock, and other pitfalls of multithreading. Developers are encouraged to identify functions of their applications that would live better executed off the main thread, even if they're made up of several sequential or otherwise partially interdependent tasks. GCD makes it simple to fracture off the entire unit of toil while maintaining the existing order and dependencies between subtasks.

    Those with some multithreaded programming experience may live unimpressed with the GCD. So Apple made a thread pool. immense deal. They've been around forever. But the angels are in the details. Yes, the implementation of queues and threads has an elegant simplicity, and baking it into the lowest levels of the OS really helps to lower the perceived barrier to entry, but it's the API built around blocks that makes majestic Central Dispatch so attractive to developers. Just as Time Machine was "the first backup system people will actually use," majestic Central Dispatch is poised to finally spread the heretofore dusky expertise of asynchronous application design to uncouth Mac OS X developers. I can't wait.

    OpenCL Somehow, OpenCL got in on the <a href="http://arstechnica.com/apple/2007/10/mac-os-x-10-5/8/#core-spheres">"core" branding</a>Somehow, OpenCL got in on the "core" branding

    So far, we've seen a few examples of doing more with more: a new, more modern compiler infrastructure that supports an vital current language feature, and a powerful, pragmatic concurrency API built on top of the current compilers' uphold for said language feature. uncouth this goes a long pass towards helping developers and the OS itself gain maximum use of the available hardware.

    But CPUs are not the only components experiencing a glut of transistors. When it comes to the proliferation of independent computation engines, another piece of silicon inside every Mac is the undisputed title holder: the GPU.

    The numbers disclose the tale. While Mac CPUs contain up to four cores (which may pomp up as eight ratiocinative cores thanks to symmetric multithreading), high-end GPUs contain well over 200 processor cores. While CPUs are just now edging over 100 GFLOPS, the best GPUs are capable of over 1,000 GFLOPS. That's one trillion floating-point operations per second. And enjoy CPUs, GPUs now foster more than one on a board.

    Writing for the GPU

    Unfortunately, the cores on a GPU are not general-purpose processors (at least not yet). They're much simpler computing engines that Have evolved from the fixed-function silicon of their ancestors that could not live programmed directly at all. They don't uphold the moneyed set of instructions available on CPUs, the maximum size of the programs that will evade is often limited and very small, and not uncouth of the features of the industry-standard IEEE floating-point computation specification are supported.

    Today's GPUs can live programmed, but the most common forms of programmability are quiet firmly planted in the world of graphics programming: vertex shaders, geometry shaders, pixel shaders. Most of the languages used to program GPUs are similarly graphically focused: HLSL, GLSL, Cg.

    Nevertheless, there are computational tasks outside the realm of graphics that are a benign apt for GPU hardware. It would live nice if there were a non-graphics-oriented language to write them in. Creating such a thing is quite a challenge, however. GPU hardware varies wildly in every imaginable way: number and character of execution units, available data formats, instruction sets, remembrance architecture, you title it. Programmers don't want to live exposed to these differences, but it's difficult to toil around the complete want of a feature or the unavailability of a particular data type.

    GPU vendor NVIDIA gave it a shot, however, and produced CUDA: a subset of the C language with extensions for vector data types, data storage specifiers that reflect typical GPU remembrance hierarchy, and several bundled computational libraries. CUDA is but one entrant in the burgeoning GPGPU domain (General-Purpose computing on Graphics Processing Units). But coming from a GPU vendor, it faces an uphill battle with developers who really want a vendor-agnostic solution.

    In the world of 3D programming, OpenGL fills that role. As you've surely guessed by now, OpenCL aims to conclude the very for general-purpose computation. In fact, OpenCL is supported by the very consortium as OpenGL: the ominously named Khronos Group. But gain no mistake, OpenCL is Apple's baby.

    Apple understood that OpenCL's best haphazard of success was to become an industry standard, not just an Apple technology. To gain that happen, Apple needed the cooperation of the top GPU vendors, plus an agreement with an established, widely-recognized standards body. It took a while, but now it's uncouth foster together.

    OpenCL is a lot enjoy CUDA. It uses a C-like language with the vector extensions, it has a similar model of remembrance hierarchy, and so on. This is no surprise, considering how closely Apple worked with NVIDIA during the evolution of OpenCL. There's besides no pass any of the immense GPU vendors would radically alter their hardware to uphold an as-yet-unproven standard, so OpenCL had to toil well with GPUs already designed to uphold CUDA, GLSL, and other existing GPU programming languages.

    The OpenCL difference

    This is uncouth well and good, but to Have any impact on the day-to-day life of Mac users, developers actually Have to use OpenCL in their applications. Historically, GPGPU programming languages Have not seen much use in traditional desktop applications. There are several reasons for this.

    Early on, writing programs for the GPU often required the use of vendor-specific assembly languages that were far removed from the experience of writing a typical desktop application using a contemporaneous GUI API. The more C-like languages that came later remained either graphics-focused, vendor-specific, or both. Unless running code on the GPU would accelerate a core component of an application by an order of magnitude, most developers quiet could not live bothered to navigate this foreign world.

    And even if the GPU did give a huge quicken boost, relying on graphics hardware for general-purpose computation was very likely to narrow the potential audience for an application. Many older GPUs, especially those found in laptops, cannot evade languages enjoy CUDA at all.

    Apple's key determination in the design of OpenCL was to allow OpenCL programs to evade not just on GPUs, but on CPUs as well. An OpenCL program can query the hardware it's running on and enumerate uncouth eligible OpenCL devices, categorized as CPUs, GPUs, or dedicated OpenCL accelerators (the IBM Cell Blade server—yes, that Cell—is apparently one such device). The program can then dispatch its OpenCL tasks to any available device. It's besides workable to create a unique ratiocinative device consisting of any combination of eligible computing resources: two GPUs, a GPU and two CPUs, etc.

    The advantages of being able to evade OpenCL programs on both CPUs and GPUs are obvious. Every Mac running Snow Leopard, not just those with the recent-model GPUs, can evade a program that contains OpenCL code. But there's more to it than that.

    Certain kinds of algorithms actually evade faster on high-end multi-core CPUs than on even the very fastest available GPUs. At WWDC 2009, an engineer from Electronic Arts demonstrated an OpenCL port of a skinning engine from one of its games running over four times faster on a four-core Mac Pro than on an NVIDIA GeForce GTX285. Restructuring the algorithm and making many other changes to better suit the limitations (and strengths) of the GPU pushed it back ahead of the CPU by a wide margin, but sometimes you just want the system you Have to evade well as-is. Being able to target the CPU is extremely useful in those cases.

    Moreover, writing vector code for Intel CPUs "the old-fashioned way" can live a actual pain. There's MMX, SSE, SSE2, SSE3, and SSE4 to deal with, uncouth with slightly different capabilities, and uncouth of which compel the programmer to write code enjoy this:

    r1 = _mm_mul_ps(m1, _mm_add_ps(x1, x2));

    OpenCL's indigenous uphold for vector types de-clutters the code considerably:

    r1 = m1 * (x1 + x2);

    Similarly, OpenCL's uphold for implicit parallelism makes it much easier to seize edge of multiple CPU cores. Rather than writing uncouth the logic to split your data into pieces and dole those pieces to the parallel-computing hardware, OpenCL lets you write just the code to operate on a unique piece of the data and then ship it, along with the entire shroud of data and the desired flush of parallelism, to the computing device.

    This arrangement is taken for granted in traditional graphics programming, where code implicitly works on uncouth pixels in a texture or uncouth vertices in a polygon; the programmer only needs to write code that will exist in the "inner loop," so to speak. An API with uphold for this kindhearted of parallelism that runs on CPUs as well as GPUs fills an vital gap.

    Writing to OpenCL besides future-proofs task- or data-parallel code. Just as the very OpenGL code will accept faster and faster as newer, more powerful GPUs are released, so too will OpenCL code achieve better as CPUs and GPUs accept faster. The extra layer of abstraction that OpenCL provides makes this possible. For example, though vector code written several years ago using MMX got faster as CPU clock speeds increased, a more significant performance boost likely requires porting the code to one of the newer SSE instruction sets.

    As newer, more powerful vector instruction sets and parallel hardware becomes available, Apple will update its OpenCL implementations to seize edge of them, just as video card makers and OS vendors update their OpenGL drivers to seize edge of faster GPUs. Meanwhile, the application developer's code remains unchanged. Not even a recompile is required.

    Here live dragons (and trains)

    How, you may wonder, can the very compiled code discontinuance up executing using SSE2 on one machine and SSE4 on another, or on an NVIDIA GPU on one machine and an ATI GPU on another? To conclude so would require translating the device-independent OpenCL code to the instruction set of the target computing device at runtime. When running on a GPU, OpenCL must besides ship the data and the newly translated code over to the video card and collect the results at the end. When running on the CPU, OpenCL must sort for the requested flush of parallelism by creating and distributing threads appropriately to the available cores.

    Well, wouldn't you know it? Apple just happens to Have two technologies that decipher these exact problems.

    Want to compile code "just in time" and ship it off to a computing device? That's what LLVM was born to do—and, indeed, what Apple did with it in Leopard, albeit on a more limited scale. OpenCL is a natural extension of that work. LLVM allows Apple to write a unique code generator for each target instruction set, and concentrate uncouth of its application on a unique device-independent code optimizer. There's no longer any exigency to duplicate these tasks, using one compiler to create the static application executable and having to jury-rig another for just-in-time compilation.

    (Oh, and by the way, bethink Core Image? That's another API that needs to compile code just-in-time and ship it off to execute on parallel hardware enjoy GPUs and multi-core CPUs. In Snow Leopard, Core Image has been re-implemented using OpenCL, producing a hefty 25% overall performance boost.)

    To ply task parallelism and provision threads, OpenCL is built on top of majestic Central Dispatch. This is such a natural apt that it's a bit surprising that the OpenCL API doesn't use blocks. I judge Apple decided that it shouldn't press its luck when it comes to getting its home-grown technologies adopted by other vendors. This determination already seems to live paying off, as AMD has its own OpenCL implementation under way.

    The top of the pyramid

    Though the underlying technologies, Clang, blocks and majestic Central Dispatch, will undoubtedly live more widely used by developers, OpenCL represents the culmination of that particular technological thread in Snow Leopard. This is the gold benchmark of software engineering: creating a current public API by pile it on top of lower-level, but equally well-designed and implemented public APIs.

    A unified abstraction for the ever-growing heterogeneous collection of parallel computing silicon in desktop computers was sorely needed. We've got an increasing population of powerful CPU cores, but they quiet exist in numbers that are orders of magnitude lower than the hundreds of processing units in modern GPUs. On the other hand, GPUs quiet Have a ways to Go to entrap up with the power and flexibility of a full-fledged CPU core. But even with uncouth the differences, writing code exclusively for either one of those worlds quiet smacks of leaving money on the table.

    With OpenCL in hand, there's no longer a exigency to set aside uncouth your eggs in one silicon basket. And with the advent of hybrid CPU/GPU efforts enjoy Intel's Larabee, which use CPU-caliber processing engines, but in much higher numbers, OpenCL may prove even more vital in the coming years.

    Transistor harvest

    Collectively, the concurrency-enabling features introduced in Snow Leopard picture the biggest boost to asynchronous and parallel software evolution in any Mac OS X release—perhaps in any desktop operating system release ever. It may live difficult for end-users to accept excited about "plumbing" technologies enjoy majestic Central Dispatch and OpenCL, let alone compilers and programming language features, but it's upon these foundations that developers will create ever-more-impressive edifices of software. And if those applications tower over their synchronous, serial predecessors, it will live because they stand on the shoulders of giants.

    QuickTime Player's  current icon (Not a fan)QuickTime Player's current icon (Not a fan) QuickTime Player

    There's been some confusion surrounding QuickTime in Snow Leopard. The earlier section about QuickTime X explains what you exigency to know about the present and future of QuickTime as a technology and an API. But a few of Apple's decisions—and the extremely overloaded significance of the word "QuickTime" in the minds of consumers—have blurred the picture somewhat.

    The first head-scratcher occurs during installation. If you occur to click on the "Customize…" button during installation, you'll behold the following options:

    QuickTime 7 is an optional install?QuickTime 7 is an optional install?

    We've already talked about Rosetta being an optional install, but QuickTime 7 too? Isn't QuickTime severely crippled without QuickTime 7? Why in the world would that live an optional install?

    Well, there's no exigency to panic. That detail in the installer should actually read "QuickTime Player 7." QuickTime 7, the traditional but extremely capable media framework discussed earlier, is installed by default in Snow Leopard—in fact, it's mandatory. But the player application, the one with the traditional blue "Q" icon, the one that many casual users actually judge of as being "QuickTime," that's been replaced with a current QuickTime-X-savvy version sporting a pudgy current icon (see above right).

    The current player application is a immense departure from the old. Obviously, it leverages QuickTime X for more efficient video playback, but the user interface is besides completely new. Gone are the gray edge and bottom-mounted playback controls from the traditional QuickTime Player, replaced by a frameless window with a black title bar and a floating, moveable set of controls.

    The  current QuickTime Player: boldly going where <a href="http://code.google.com/p/niceplayer/">NicePlayer</a> has gone before Enlarge / The current QuickTime Player: boldly going where NicePlayer has gone before

    It's enjoy a combination of the window treatment of the excellent NicePlayer application and the full-screen playback controls from the traditional QuickTime Player. I'm a bit bothered by two things. First, the ever-so-slightly clipped corners seem enjoy a inferior idea. Am I just supposed to give up those dozen-or-so pixels? NicePlayer does it right, showing crisp, square corners.

    Second, the floating playback controls obscure the movie. What if I'm scrubbing around looking for something in that piece of the frame? Yes, you can Move the controls, but what if I'm looking for something in an unknown location in the frame? Also, the title bar obscures an entire swath of the top of the frame, and this can't live moved. I value the compactness of this approach, but it'd live nice if the title bar overlap could live disabled and the controls could live dragged off the movie entirely and docked to the bottom or something.

    (One blessing for people who partake my OCD tendencies: if you Move the floating controls, they don't bethink their position the next time you open a movie. Why is that a blessing? Because if it worked the other way, we'd uncouth expend pass too much time fretting about their inability to restore the controller to its default, precisely centered position. Sad, but true.)

    The current QuickTime Player presents a decidedly iMovie-like (or is it iPhone-like, nowadays?) interface for trimming video. Still-frame thumbnails are placed side-by-side to configuration a timeline, with adjustable stops at each discontinuance for trimming.

    Trimming in the  current QuickTime Player Enlarge / Trimming in the current QuickTime Player

    Holding down the option key changes from a thumbnail timeline to an audio waveform display:

    Trimming with audio waveform view Enlarge / Trimming with audio waveform view

    In both the video and audio cases, I Have to sensation exactly how useful the fancy timeline appearances are. The audio waveform is quite petite and compressed, and the limited horizontal space of the in-window pomp means a movie can only pomp a handful of video frames in its timeline. Also, if there's any aptitude to conclude fine adjustments using something other than extremely watchful mouse movements (which are necessarily matter to a limited resolution) then I couldn't find it. Final nick Pro this is not.

    QuickTime Player has learned another current trick: screen recording. The controls are limited, so more demanding users will quiet Have a exigency for a full-featured screen recorder, but QuickTime Player gets the job done.

    Screen recording in QuickTime PlayerScreen recording in QuickTime Player

    There's besides an audio-only option, with a similarly simplified collection of settings.

    Audio recordingAudio recording

    Finally, the current QuickTime Player has the aptitude to upload a movie directly to YouTube and MobileMe, ship one via e-mail, or add it to your iTunes library. The export options are besides vastly simplified, with preset options for iPhone/iPod, Apple TV, and HD 480p and 720p.

    Unfortunately, the list of things you can't conclude with the current QuickTime Player is quite long. You can't cut, copy, and paste whimsical portions of a movie (trimming only affects the ends); you can't extract or delete individual tracks or overlay one track onto another (optionally scaling to fit); you can't export a movie by choosing from the complete set of available QuickTime audio and video codecs. uncouth of these things were workable with the traditional QuickTime Player—if, that is, you paid the $30 for a QuickTime Pro license. In the past, I've described this extra fee as "criminally stupid", but the features it enabled in QuickTime Player were really useful.

    It's tempting to attribute their absence in the current QuickTime Player to the previously discussed limitations of QuickTime X. But the current QuickTime Player is built on top of QTKit, which serves as a front-end for both QuickTime X and QuickTime 7. And it does, after all, feature some limited editing features enjoy trimming, plus some previously "Pro"-only features enjoy full-screen playback. Also, the current QuickTime Player can indeed play movies using third-party plug-ins—a feature clearly powered by QuickTime 7.

    Well, Snow Leopard has an extremely pleasant flabbergast waiting for you if you install the optional QuickTime Player 7. When I did so, what I got was the traditional QuickTime Player—somewhat insultingly installed in the "Utilities" folder—with uncouth of its "Pro" features permanently unlocked. Yes, the tyranny of QuickTime Pro seems to live at an end…

    QuickTime Pro: now free for everyone?QuickTime Pro: now free for everyone?

    …but perhaps the key word above is "seems," because QuickTime Player 7 does not Have uncouth "pro" features unlocked for everyone. I installed Snow Leopard onto an vacuous disk, and QuickTime 7 was not automatically installed (as it is when the installer detects an existing QuickTime Pro license on the target disk). After booting from my fresh Snow Leopard volume, I manually installed the "QuickTime 7" optional component using the Snow Leopard installer disk.

    The result for me was a QuickTime Player 7 application with uncouth pro features unlocked and with no visible QuickTime Pro registration information. I did, however, Have a QuickTime Pro license on one of the attached drives. Apparently, the installer detected this and gave me an unlocked QuickTime Player 7 application, even though the boot volume never had a QuickTime Pro license on it.

    The Dock

    The current appearance of some aspects of the Dock are accompanied by some current functionality as well. Clicking and holding on a running application's Dock icon now triggers Expos�, but only for the windows belonging to that application. Dragging a file onto a docked application icon and holding it there for a bit produces the very result. You can then continue that very drag onto one of the Exposé window thumbnails and hover there a bit to bring that window to the front and drop the file into it. It's a pretty handy technique, once you accept in the wont of doing it.

    The Exposé pomp itself is besides changed. Now, minimized windows are displayed in smaller configuration on the bottom of the screen below a thin line.

    Dock Exposé with  current placement of minimized windows Enlarge / Dock Exposé with current placement of minimized windows

    In the screenshot above, you'll notice that null of the minimized windows appear in my Dock. That's thanks to another welcome addition: the aptitude to minimize windows "into" the application icon. You'll find the setting for this in the Dock's preference pane.

    New Dock preference: Minimize windows into application iconNew Dock preference: Minimize windows into application icon Minimized windows in a Dock application menuMinimized window denoted by a diamond

    Once set, minimized windows will slip behind the icon of their parent application and then disappear. To accept them back, either right-click the application icon (see right) or trigger Exposé.

    The Dock's grid view for folders now incorporates a scroll bar when there are too many items to apt comfortably. Clicking on a folder icon in the grid now shows that folder's contents within the grid, allowing you to navigate down several folders to find a buried item. A petite "back" navigation button appears once you descend.

    These are uncouth useful current behaviors, and quite a premium considering the supposed "no current features" stance of Snow Leopard. But the fundamental nature of the Dock remains the same. Users who want a more flexible or more powerful application launcher/folder organizer/window minimization system must quiet either sacrifice some functionality (e.g., Dock icon badges and bounce notifications) or continue to use the Dock in addition to a third-party application.

    The option to preserve minimized windows from cluttering up the Dock was long overdue. But my enthusiasm is tempered by my frustration at the continued inability to click on a docked folder and Have it open in the Finder, while besides retaining the aptitude to drag items into that folder. This was the default deportment for docked folders for the first six years of Mac OS X's life, but it changed in Leopard. Snow Leopard does not help matters.

    Docking an alias to a folder provides the single-click-open behavior, but items cannot live dragged into a docked folder alias for some inexplicable reason. (Radar 5775786, closed in March 2008 with the terse explanation, "not currently supported.") Worse, dragging an detail to a docked folder alias looks enjoy it will toil (the icon highlights) but upon release, the dragged detail simply springs back to its original location. I really hoped this one would accept fixed in Snow Leopard. No such luck.

    Dock grid view's in-place navigation with back buttonDock grid view's in-place navigation with back button The Finder

    One of the earliest leaked screenshots of Snow Leopard included an innocuous-looking "Get Info…" window for the Finder, presumably to pomp that its version number had been updated to 10.6. The more touching tidbit of information it revealed was that the Finder in Snow Leopard was a 64-bit application.

    The Mac OS X Finder started its life as the designated "dog food" application for the Carbon backward-compatibility API for Mac OS X. Over the years, the Finder has been a frequent target of dissatisfaction and scorn. Those inferior feelings frequently spilled over into the parallel debate over API supremacy: Carbon vs. Cocoa.

    "The Finder sucks because it's a Carbon app. What they exigency is a Cocoa Finder! Surely that will decipher uncouth their woes." Well, Snow Leopard features a 64-bit Finder, and as they uncouth know, Carbon was not ported to 64-bit. Et voila! A Cocoa Finder in Snow Leopard. (More on the woes in a bit.)

    The conversion to Cocoa followed the Snow Leopard formula: no current features… except for maybe one or two. And so, the "new" Cocoa Finder looks and works almost exactly enjoy the traditional Carbon Finder. The biggest indicator of its "Cocoa-ness" is the extensive use of Core Animation transitions. For example, when a Finder window does its schizophrenic transformation from a sidebar-bedecked browser window to its minimally-adorned form, it no longer happens in a blink. Instead, the sidebar slides away and fades, the toolbar shrinks, and everything tucks in to configuration its current shape.

    Despite crossing the line in a few cases, the Core Animation transitions conclude gain the application feel more polished, and yes, "more Cocoa." And presumably the use of Cocoa made it so darn simple to add features that the developers just couldn't resist throwing in a few.

    The number-one feature request from cumbersome column-view users has finally been implemented: sortable columns. The sort order applies to uncouth columns at once, which isn't as nice as per-column sorting, but it's much better than nothing at all. The sort order can live set using a menu command (each of which has a keyboard shortcut) or by right-clicking in an unoccupied area of a column and selecting from the resulting context menu.

    Column view sorting context menu Enlarge / Column view sorting context menu Column view sorting menu Enlarge / Column view sorting menu

    Even the lowly icon view has been enhanced in Snow Leopard. Every icon-view window now includes a petite slider to control the size of the icons.

    The Finder's icon view with its  current slider controlThe Finder's icon view with its current slider control

    This may seem a bit odd—how often conclude people change icon sizes?—but it makes much more sense in the context of previewing images in the Finder. This use case is made even more apposite by the recent expansion of the maximum icon size to 512x512 pixels.

    The icon previews themselves Have been enhanced to better match the abilities available in Quick Look. set aside it uncouth together and you can smoothly zoom a petite PDF icon, for example, into the impressively high-fidelity preview shown below, complete with the aptitude to whirl pages. One press of the space bar and you'll progress to the even larger and more flexible Quick watch view. It's a pretty smooth experience.

    Not your father's icon: 512x512 pixels of multi-page PDF previewingNot your father's icon: 512x512 pixels of multi-page PDF previewing

    QuickTime previews Have been similarly enhanced. As you zoom in on the icon, it transforms into a miniature movie player, adorned with an odd circular progress indicator. Assuming users are willing to wrangle with the vagaries of the Finder's view settings successfully enough to accept icon view to stick for the windows where it's most useful, I judge that odd itsy-bitsy slider is actually going to accept a lot of use.

    The Finder's QuickTime preview. (The "glare" overlay is a bit much.)The Finder's QuickTime preview. (The "glare" overlay is a bit much.)

    List view besides has a few enhancements—accidental, incidental, or otherwise. The drag area for each list view detail now spans the entire line. In Leopard, though the entire line was highlighted, only the file title or icon portion could live dragged. Trying to drag anywhere else just extended the selection to other items in the list view as the cursor was moved. I'm not positive whether this change in deportment is intentional or if it's just an unexamined consequence of the underlying control used for list view in the current Cocoa Finder. Either way, thumbs up.

    Double-clicking on the dividing line between two column headers in list view will "right-size" that column. For most columns, this means expanding or shrinking to minimally apt the widest value in the column. Date headers will progressively shrink to pomp less verbose date formats. Supposedly, this worked intermittently in Leopard as well. But whether Cocoa is bringing this feature for the first time or is just making it toil correctly for the first time, it's a change for the better.

    Searching using the Finder's browser view is greatly improved by the implementation of one of those itsy-bitsy things that many users Have been clamoring for year after year. There's now a preference to select the default scope of the search domain in the Finder window toolbar. Can I accept an amen?

    Default Finder search location: configurable at last.Default Finder search location: configurable at last.

    Along similar lines, there are other long-desired enhancements that will Go a long pass towards making the desktop environment feel more solid. A benign illustration is the improved handling of the dreaded "cannot eject, disk in use" error. The obvious follow-up question from the user is, "Okay, so what's using it?" Snow Leopard finally provides that information.

    No more guessingNo more guessing

    (Yes, Mac OS X will rebuff to dismiss a disk if your current working directory in a command-line shell is on that disk. kindhearted of cool, but besides kindhearted of annoying.)

    Another workable user response to a disk-in-use oversight is, "I don't care. I'm in a hurry. Just dismiss it!" That's an option now as well.

    Forcible ejection in progressForcible ejection in progress

    Hm, but why did I accept information about the offending application in one dialog, an option to compel ejection in the other, but neither one presented both choices? It's a mystery to me, but presumably it's related to exactly what information the Finder has about the contention for the disk. (As always, the lsof command is available if you want to device it out the old-fashioned way.)

    Ummm…Ummm…

    So does the current Cocoa Finder finally extradite uncouth of those embarrassing bugs from the bad-old days of Carbon? Not quite. This is essentially the "1.0" release of the Cocoa Finder, and it has its partake of 1.0 bugs. Here's one discovered by Glen Aspeslagh (see image right).

    Do you behold it? If not, watch closer at the order of the dates in the supposedly sorted "Date Modified" column. So yeah, that traditional Finder magic has not been entirely extinguished.

    There besides remains some weirdness in the operation of the icon grid. In a view where grid snap is turned on (or is enabled transiently by holding down the command key during a drag) icons seem terrified of each other, leaving huge distances between themselves and their neighbors when they select which grid spot to snap to. It's as if the Finder lives in mortal tocsin that one of these files will someday accept a 200-character filename that will overlap with a neighboring file's name.

    The worst incarnation of this deportment happens along the privilege edge of the screen where mounted volumes appear on the desktop. (Incidentally, this is not the default; if you want to behold disks on your desktop, you must enable this preference in the Finder.) When I mount a current disk, I'm often surprised to behold where it ends up appearing. If there are any icons remotely immediate to the privilege edge of the screen, the disk icon will rebuff to appear there. Again, the Finder is not avoiding any actual title or icon overlapping. It appears to live avoiding the mere possibility of overlapping at some unspecified point in the future. Silly.

    Finder report card

    Overall, the Snow Leopard Finder takes several significant steps forward—64-bit/Cocoa future-proofing, a few new, useful features, added polish—and only a few shuffles backwards with the slight overuse of animation and the continued presence of some puzzling bugs. Considering how long it took the Carbon Finder to accept to its pre-Snow-Leopard feature set and flush of polish, it's quite an achievement for a Cocoa Finder to match or exceed its predecessor in its very first release. I'm positive the Carbon vs. Cocoa warriors would Have had a domain day with that statement, were Carbon not set aside out to pasture in Leopard. But it was, and to the victor Go the spoils.

    Exchange

    Snow Leopard's headline "one current feature" is uphold for Microsoft Exchange. This appears to be, at least partially, yet another hand-me-down from the iPhone, which gained uphold for Exchange in its 2.0 release and expanded on it in 3.0. Snow Leopard's Exchange uphold is weaved throughout the expected crop of applications in Mac OS X: iCal, Mail, and Address Book.

    The immense caveat is that it will only toil with a server running Exchange 2007 (Service Pack 1, Update Rollup 4) or later. While I'm positive Microsoft greatly appreciates any additional upgrade revenue this determination provides, it means that for users whose workplaces are quiet running older versions of Exchange, Snow Leopard's "Exchange support" might as well not exist.

    Those users are probably already running the only other viable Mac OS X Exchange client, Microsoft Entourage, so they'll likely just sit tense and wait for their IT departments to upgrade. Meanwhile, Microsoft is already making overtures to these users with the promised creation—finally—of an honest-to-goodness version of Outlook for Mac OS X.

    In my admittedly brief testing, Snow Leopard's Exchange uphold seems to toil as expected. I had to Have one of the Microsoft mavens in the Ars Orbiting HQ spin up an Exchange 2007 server just for the purposes of this review. However it was configured, uncouth I had to enter in the Mail application was my complete name, e-mail address, and password, and it automatically discovered uncouth apposite settings and configured iCal and Address bespeak for me.

    Exchange setup: surprisingly easyExchange setup: surprisingly easy

    Windows users are no doubt accustomed to this kindhearted of Exchange integration, but it's the first time I've seen it on the Mac platform—and that includes my many years of using Entourage.

    Access to Exchange-related features is decidedly subdued, in keeping with the existing interfaces for Mail, iCal, and Address Book. If you're expecting the swarm of panels and toolbar buttons found in Outlook on Windows, you're in for a bit of a shock. For example, here's the "detail" view of a meeting in iCal.

    iCal event detailiCal event detail

    Clicking the "edit" button hardly reveals more.

    Event editor: that's it?Event editor: that's it?

    The "availability" window besides includes the bare minimum number of controls and displays to accept the job done.

    Meeting availability checker Enlarge / Meeting availability checker

    The integration into Mail and Address bespeak is even more subtle—almost entirely transparent. This is to live construed as a feature, I suppose. But though I don't know enough about Exchange to live completely sure, I can't tremble the sentiment that there are Exchange features that remain inaccessible from Mac OS X clients. For example, how conclude I bespeak a "resource" in a meeting? If there's a pass to conclude so, I couldn't determine it.

    Still, even basic Exchange integration out-of-the-box goes long pass towards making Mac OS X more welcome in corporate environments. It remains to live seen how convinced IT managers are of the "realness" of Snow Leopard's Exchange integration. But I've got to judge that being able to ship and receive mail, create and respond to meeting invitations, and use the global corporate address bespeak is enough for any Mac user to accept along reasonably well in an Exchange-centric environment.

    Performance

    The thing is, there's not really much to shriek about performance in Snow Leopard. Dozens of benchmark graphs lead to the very simple conclusion: Snow Leopard is faster than Leopard. Not shockingly so, at least in the aggregate, but it's faster. And while isolating one particular subsystem with a micro-benchmark may divulge some impressive numbers, it's the pass these petite changes combine to help the real-world experience of using the system that really makes a difference.

    One illustration Apple gave at WWDC was making an initial Time Machine backup over the network to a Time Capsule. Apple's approach to optimizing this operation was to address each and every subsystem involved.

    Time Machine itself was given uphold for overlapping i/o. Spotlight indexing, which happens on Time Machine volumes as well, was identified as another time-consuming task involved in backups, so its performance was improved. The networking code was enhanced to seize edge of hardware-accelerated checksums where possible, and the software checksum code was hand-tuned for maximum performance. The performance of HFS+ journaling, which accompanies each file system metadata update, was besides improved. For Time Machine backups that write to disk images rather than indigenous HFS+ file systems, Apple added uphold for concurrent access to disk images. The amount of network traffic produced by AFP during backups has besides been reduced.

    All of this adds up to a respectable 55% overall improvement in the quicken of an initial Time Machine backup. And, of course, the performance improvements to the individual subsystems benefit uncouth applications that use them, not just Time Machine.

    This holistic approach to performance improvement is not likely to knock anyone's socks off, but every time you evade across a piece of functionality in Snow Leopard that disproportionately benefits from one of these optimized subsystems, it's a pleasure.

    For example, Snow Leopard shuts down and restarts much faster than Leopard. I'm not talking about boot time; I weigh in the time between the selection of the Shutdown or Restart command and when the system turns off or begins its current boot cycle. Leopard doesn't seize long at uncouth to conclude this; only a few dozen of seconds when there are no applications open. But in Snow Leopard, it's so enjoy a gleam that I often thought the operating system had crashed rather than shut down cleanly. (That's actually not too far from the truth.)

    The performance boosts offered by earlier major releases of Mac OS X quiet dwarf Snow Leopard's speedup, but that's mostly because Mac OS X was so excruciatingly sluggish in its early years. It's simple to create a immense performance delta when you're starting from something abysmally slow. The fact that Snow Leopard achieves consistent, measurable improvements over the already-speedy Leopard is uncouth the more impressive.

    And yes, for the seventh consecutive time, a current release of Mac OS X is faster on the very hardware than its predecessor. (And for the first time ever, it's smaller, too.) What more can you quiz for, really? Even that traditional performance bugaboo, window resizing, has been completely vanquished. Grab the corner of a fully-populated iCal window—the worst-case scenario for window resizing in the traditional days—and tremble it as enjoy a gleam as you can. Your cursor will never live more than a few millimeters from the window's grab handle; it tracks your frantic motion perfectly. On most Macs, this is actually steady in Leopard as well. It just goes to pomp how far Mac OS X has foster on the performance front. These days, they uncouth just seize it for granted, which is exactly the pass it should be.

    Grab bag

    In the "grab bag" section, I usually examine smaller, mostly unrelated features that don't warrant full-blown sections of their own. But when it comes to user-visible features, Snow Leopard is kindhearted of "all grab bag," if you know what I mean. Apple's even got its own incarnation in the configuration of a giant webpage of "refinements." I'll probably overlap with some of those, but there'll live a few current ones here as well.

    New columns in open/save dialogs

    The list view in open and save dialog boxed now supports more than just "Name" and "Date Modified" columns. Right-click on any column to accept a preference of additional columns to display. I've wanted this feature for a long time, and I'm joyous someone finally had time to implement it.

    Configurable columns in open/save dialogsConfigurable columns in open/save dialogs Improved scanner support

    The bundled Image Capture application now has the aptitude to talk to a wide achieve of scanners. I plugged in my Epson Stylus CX7800, a device that previously required the use of third-party software in order to use the scanning feature, and Image Capture detected it immediately.

    Epson scanner + Image Capture - Epson software Enlarge / Epson scanner + Image Capture - Epson software

    Image Capture is besides not a inferior itsy-bitsy scanning application. It has pretty benign automatic remonstrate detection, including uphold for multiple objects, obviating the exigency to manually crop items. Given the sometimes-questionable trait of third-party printer and scanner drivers for Mac OS X, the aptitude to use a bundled application is welcome.

    System Preferences bit wars

    System Preferences, enjoy virtually uncouth other applications in Snow Leopard, is 64-bit. But since 64-bit applications can't load 32-bit plug-ins, that presents a problem for the existing crop of 32-bit third-party preference panes. System Preferences handles this situation with a reasonable amount of grace. On launch, it will pomp icons for uncouth installed preference panes, 64-bit or 32-bit. But if you click on a 32-bit preference pane, you'll live presented with a notification enjoy this:

    64-bit application vs. 32-bit plug-in: fight!64-bit application vs. 32-bit plug-in: fight!

    Click "OK" and System Preferences will relaunch in 32-bit mode, which is conveniently indicated in the title bar. Since uncouth of the first-party preference panes are compiled for both 64-bit and 32-bit operation, System Preferences does not exigency to relaunch again for the duration of its use. This raises the question, why not Have System Preferences launch in 32-bit mode uncouth the time? I suspect it's just another pass for Apple to "encourage" developers to build 64-bit-compatible binaries.

    Safari plug-ins

    The inability of of 64-bit applications load 32-bit plug-ins is a problem for Safari as well. Plug-ins are so vital to the Web experience that relaunching in 32-bit mode is not really an option. You'd probably exigency to relaunch as soon as you visited your first webpage. But Apple does want Safari to evade in 64-bit mode due to some significant performance enhancements in the JavaScript engine and other areas of the application that are not available in 32-bit mode.

    Apple's solution is similar to what it did with QuickTime X and 32-bit QuickTime 7 plug-ins. Safari will evade 32-bit plug-ins in separate 32-bit processes as needed.

    Separate processes for 32-bit Safari plug-insSeparate processes for 32-bit Safari plug-ins

    This has the added, extremely significant benefit of isolating potentially buggy plug-ins. According to the automated crash reporting built into Mac OS X, Apple has said that the number one cause of crashes is Web browser plug-ins. That's not the number one cause of crashes in Safari, mind you, it's the number one cause when considering uncouth crashes of uncouth applications in Mac OS X. (And though it was not mentioned by name, I judge they uncouth know the primary culprit.)

    As you can behold above, the QuickTime browser plug-in gets the very treatment as gleam and other third-party 32-bit Safari plug-ins. uncouth of this means that when a plug-in crashes, Safari in Snow Leopard does not. The window or tab containing the crashing plug-in doesn't even close. You can simply click the reload button and give the problematic plug-in another haphazard to office correctly.

    While this is quiet far from the much more robust approach employed by Google Chrome, where each tab lives in its own independent process, if Apple's crash statistics are to live believed, isolating plug-ins may generate most of the benefit of truly separate processes with a significantly less radical change to the Safari application itself.

    Resolution independence

    When they terminal left Mac OS X in its seemingly interminable march towards a truly scalable user interface, it was almost ready for prime time. I'm unhappy to shriek that resolution independence was obviously not a priority in Snow Leopard, because it hasn't gotten any better, and may Have actually regressed a bit. Here's what TextEdit looks enjoy at a 2.0 scale factor in Leopard and Snow Leopard.

    TextEdit at scale factor 2.0 in LeopardTextEdit at scale factor 2.0 in Leopard TextEdit at scale factor 2.0 in Snow LeopardTextEdit at scale factor 2.0 in Snow Leopard

    Yep, it's a bummer. I quiet bethink Apple advising developers to Have their applications ready for resolution independence by 2008. That's one of the few dates that the Jobs-II-era Apple has not been able to hit, and it's getting later uncouth the time. On the other hand, it's not enjoy 200-DPI monitors are raining from the sky either. But I'd really enjoy to behold Apple accept going on this. It will undoubtedly seize a long time for everything to watch and toil correctly, so let's accept started.

    Terminal splitters

    The Terminal application in Tiger and earlier versions of Mac OS X allowed each of its windows to live split horizontally into two separate panes. This was invaluable for referencing some earlier text in the scrollback while besides typing commands at the prompt. Sadly, the splitter feature disappeared in Leopard. In Snow Leopard, it's back with a vengeance.

    Arbitrary splitters, baby!Arbitrary splitters, baby!

    (Now if only my favorite text editor would accept on board the train to splittersville.)

    Terminal in Snow Leopard besides defaults to the current Menlo font. But ornery to earlier reports, the One steady Monospaced Font, Monaco, is most definitely quiet included in Snow Leopard (see screenshot above) and it works just fine.

    System Preferences shuffle

    The seemingly obligatory rearrangement of preference panes in the System Preferences application accompanying each release of Mac OS X continues in Snow Leopard.

    System Preferences: shuffled yet again Enlarge / System Preferences: shuffled yet again System Preferences (not running) with Dock menuSystem Preferences (not running) with Dock menu

    This time, the "Keyboard & Mouse" preference pane is split into separate "Keyboard" and "Mouse" panes, "International" becomes "Language & Text," and the "Internet & Network" section becomes "Internet & Wireless" and adopts the Bluetooth preference pane.

    Someday in the remote future, perhaps Apple will finally arrive at the "ultimate" arrangement of preference panes and they can uncouth finally Go more than two years without their muscle remembrance being disrupted.

    Before touching on, System Preferences has one trim trick. You can launch directly into a specific preference pane by right-clicking on System Preferences's Dock icon. This works even when System Preferences is not yet running. kindhearted of creepy, but useful.

    Core location

    One more gift from the iPhone, Core Location, allows Macs to device out where in the world they are. The "Date & Time" preference pane offers to set your time zone automatically based on your current location using this newfound ability.

    Set your Mac's time zone automatically based on your current location, thanks to Core Location.Set your Mac's time zone automatically based on your current location, thanks to Core Location. Keyboard magic

    Snow Leopard includes a simple facility for system-wide text auto-correction and expansion, accessible from the "Language & Text" preference pane. It's not quite ready to give a dedicated third-party application a evade for its money, but hey, it's free.

    Global text expansion and auto-correction Enlarge / Global text expansion and auto-correction

    The keyboard shortcuts preference pane has besides been rearranged. Now, instead of a single, long list of system-wide keyboard shortcuts, they're arranged into categories. This reduces clutter, but it besides makes it a bit more difficult to find the shortcut you're interested in.

    Keyboard shortcuts: now with categories Enlarge / Keyboard shortcuts: now with categories The sleeping Mac dilemma

    I don't enjoy to leave my Mac Pro turned on 24 hours a day, especially during the summer in my un-air-conditioned house. But I conclude want to Have access to the files on my Mac when I'm elsewhere—at work, on the road, etc. It is workable to wake a sleeping Mac remotely, but doing so requires being on the very local network.

    My solution has been to leave a smaller, more power-efficient laptop on at uncouth times on the very network as my Mac Pro. To wake my Mac Pro remotely, I ssh into the laptop, then ship the magic "wake up" packet to my Mac Pro. (For this to work, the "Wake for Ethernet network administrator access" checkbox must live checked in the "Energy Saver" preference pane in System Preferences.)

    Snow Leopard provides a pass to conclude this without leaving any of my computers running uncouth day. When a Mac running Snow Leopard is set aside to sleep, it attempts to hand off ownership of its IP address to its router. (This only works with an AirPort Extreme ground station from 2007 or later, or a Time Capsule from 2008 or later with the latest (7.4.2) firmware installed.) The router then listens for any attempt to connect to the IP address. When one occurs, it wakes up the original owner, hands back the IP address, and forwards traffic appropriately.

    You can even wake some recent-model Macs over WiFi. Combined with MobileMe's "Back to My Mac" dynamic DNS thingamabob, it means I can leave uncouth my Macs asleep and quiet Have access to their contents anytime, anywhere.

    Back to my hack

    As has become traditional, this current release of Mac OS X makes life a bit harder for developers whose software works by patching the in-memory representation of other running applications or the operating system itself. This includes Input Managers, SIMBL plug-ins, and of course the dreaded "Haxies."

    Input Managers accept the worst of it. They've actually been unsupported and non-functional in 64-bit applications since Leopard. That wasn't such a immense deal when Mac OS X shipped with a whopping two 64-bit applications. But now, with almost every application in Snow Leopard going 64-bit, it's suddenly very significant.

    Thanks to Safari's want of an officially sanctioned extension mechanism, developers looking to enhance its functionality Have most often resorted to the use of Input Managers and SIMBL (which is an Input-Manager-based framework). A 64-bit Safari puts a damper on that entire market. Though it is workable to manually set Safari to launch in 32-bit mode—Get Info on the application in the Finder and click a checkbox—ideally, this is not something developers want to compel users to do.

    Happily, at least one commonly used Safari enhancement has the benign fortune to live built on top of the officially supported browser plug-in API used by Flash, QuickTime, etc. But that may not live a feasible approach for Safari extensions that enhance functionality in ways not tied directly to the pomp of particular types of content within a webpage.

    Though I objective to evade Safari in its default 64-bit mode, I'll really miss Saft, a Safari extension I use for session restoration (yes, I know Safari has this feature, but it's activated manually—the horror) and address bar shortcuts (e.g., "w noodles" to watch up "noodles" in Wikipedia). I'm hoping that ingenious developers will find a pass to overcome this current challenge. They always seem to, in the end. (Or Apple could add a proper extension system to Safari, of course. But I'm not holding my breath.)

    As for the Haxies, those usually fracture with each major operating system update as a matter of course. And each time, those determined fellows at Unsanity, against uncouth odds, manage to preserve their software working. I salute them for their effort. I delayed upgrading to Leopard for a long time based solely on the absence of my beloved WindowShade X. I hope I don't Have to wait too long for a Snow-Leopard-compatible version.

    The universal trend in Mac OS X is away from any sort of involuntary remembrance space sharing, and towards "external" plug-ins that live in their own, separate processes. Even contextual menu plug-ins in the Finder Have been disabled, replaced by an enhanced, but quiet less-powerful Services API. Again, I Have faith that developers will adapt. But the waiting is the hardest part.

    ZFS MIA

    It looks enjoy we'll uncouth live waiting a while longer for a file system in shining armor to replace the venerable HFS+ (11 years young!) as the default file system in Mac OS X. Despite rumors, outright declarations, and much actual pre-release code, uphold for the impressive ZFS file system is not present in Snow Leopard.

    That's a shame because Time Machine veritably cries out for some ZFS magic. What's more, Apple seems to agree, as evidenced by a post from an Apple employee to a ZFS mailing list terminal year. When asked about a ZFS-savvy implementation of Time Machine, the reply was encouraging: "This one is vital and likely will foster sometime, but not for SL." ("SL" is short for Snow Leopard.)

    There are many reasons why ZFS (or a file system with similar features) is a consummate apt for Time Machine, but the most vital is its aptitude to ship only the block-level changes during each backup. As Time Machine is currently implemented, if you gain a petite change to a giant file, the entire giant file is copied to the Time Machine volume during the next backup. This is extremely wasteful and time consuming, especially for great files that are modified constantly during the day (e.g., Entourage's e-mail database). Time Machine running on top of ZFS could transfer just the changed disk blocks (a maximum of 128KB each in ZFS, and usually much smaller).

    ZFS would besides bring vastly increased robustness for data and metadata, a pooled storage model, constant-time snapshots and clones, and a pony. People sometimes quiz what, exactly, is wrong with HFS+. Aside from its obvious want of the features just listed, HFS+ is limited in many ways by its dated design, which is based on HFS, a twenty-five year-old file system.

    To give just one example, the centrally located Catalog File, which must live updated for each change to the file system's structure, is a frequent and inevitable source of contention. Modern file systems usually spread their metadata around, both for robustness (multiple copies are often kept in separate locations on the disk) and to allow for better concurrency.

    Practically speaking, judge about those times when you evade Disk Utility on an HFS+ volume and it finds (and hopefully repairs) a bunch of errors. That's bad, okay? That's something that should not occur with a modern, thoroughly checksummed, always-consistent-on-disk file system unless there are hardware problems (and a ZFS storage pool can actually deal with that as well). And yet it happens uncouth the time with HFS+ disks in Mac OS X when various bits of metadata accept corrupted or become out of date.

    Apple gets by year after year, tacking current features onto HFS+ with duct tape and a prayer, but at a inevitable point there simply has to live a successor—whether it's ZFS, a home-grown Apple file system, or something else entirely. My fingers are crossed for Mac OS X 10.7.

    The future soon

    Creating an operating system is as much a convivial exercise as a technological one. Creating a platform, even more so. uncouth of Snow Leopard's considerable technical achievements are not just designed to benefit users; they're besides intended to goad, persuade, and otherwise herd developers in the direction that Apple feels will live most advantageous for the future of the platform.

    For this to work, Snow Leopard has to actually find its pass into the hands of customers. The pricing helps a lot there. But even if Snow Leopard were free, there's quiet some cost to the consumer—in time, worry, software updates, etc.—when performing a major operating system upgrade. The very goes for developers who must, at the very least, certify that their existing applications evade correctly on the current OS.

    The accustomed pass to overcome this kindhearted of upgrade hesitation has been to pack the OS with current features. current features sell, and the more copies of the current operating system in use, the more motivated developers are to update their applications to not just evade on the current OS, but besides seize edge of its current abilities.

    A major operating system upgrade with "no current features" must play by a different set of rules. Every party involved expects some counterbalance to the want of current features. In Snow Leopard, developers stand to garner the biggest benefits thanks to an impressive set of current technologies, many of which cover areas previously unaddressed in Mac OS X. Apple clearly feels that the future of the platform depends on much better utilization of computing resources, and is doing everything it can to gain it simple for developers to Move in this direction.

    Though it's obvious that Snow Leopard includes fewer external features than its predecessor, I'd wager that it has just as many, if not more internal changes than Leopard. This, I fear, means that the initial release of Snow Leopard will likely suffer the typical 10.x.0 bugs. There Have already been reports of current bugs introduced to existing APIs in Snow Leopard. This is the exact contradictory of Snow Leopard's implied covenant to users and developers that it would concentrate on making existing features faster and more robust without introducing current functionality and the accompanying current bugs.

    On the other side of the coin, I imagine uncouth the teams at Apple that worked on Snow Leopard absolutely reveled in the opening to polish their particular subsystems without being burdened by supporting the marketing-driven feature-of-the-month. In any long-lived software product, there needs to live this kindhearted of release valve every few years, lest the entire code ground Go off into the weeds.

    There's been one other "no current features" release of Mac OS X. Mac OS X 10.1, released a mere six months after version 10.0, was handed out for free by Apple at the 2001 Seybold publishing conference and, later, at Apple retail stores. It was besides available from Apple's online store for $19.95 (along with a copy of Mac OS 9.2.1 for use in the Classic environment). This was a different time for Mac OS X. Versions 10.0 and 10.1 were slow, incomplete, and extremely immature; the transition from classic Mac OS was far from over.

    Judged as a modern incarnation of the 10.1 release, Snow Leopard looks pretty darned good. The pricing is similar, and the benefits—to developers and to users—are greater. So is the risk. But again, that has more to conclude with how horrible Mac OS X 10.0 was. Choosing not to upgrade to 10.1 was unthinkable. Waiting a while to upgrade to Snow Leopard is reasonable if you want to live positive that uncouth the software you keeping about is compatible. But don't wait too long, because at $29 for the upgrade, I hope Snow Leopard adoption to live quite rapid. Software that will evade only on Snow Leopard may live here before you know it.

    Should you buy Mac OS X Snow Leopard? If you're already running Leopard, then the retort is a resounding "yes." If you're quiet running Tiger, well, then it's probably time for a current Mac anyway. When you buy one, it'll foster with Snow Leopard.

    As for the future, it's tempting to view Snow Leopard as the "tick" in a current Intel-style "tick-tock" release strategy for Mac OS X: radical current features in version 10.7 followed by more Snow-Leopard-style refinements in 10.8, and so on, alternating between "feature" and "refinement" releases. Apple has not even hinted that they're considering this character of plan, but I judge there's a lot to recommend it.

    Snow Leopard is a unique and shapely release, unlike any that Have foster before it in both scope and intention. At some point, Mac OS X will surely exigency to accept back on the bullet-point-features bandwagon. But for now, I'm content with Snow Leopard. It's the Mac OS X I know and love, but with more of the things that gain it decrepit and disorderly engineered away.

    Snowy eyes Looking back

    This is the tenth review of a complete Mac OS X release, public beta, or developer preview to evade on Ars, dating back to December 1999 and Mac OS X DP2. If you want to jump into the Wayback Machine and behold how far Apple has foster with Snow Leopard (or just want to bone up on uncouth of the immense cat monikers), we've gone through the archives and dug up some of their older Mac OS X articles. gratified reading!

  • Five years of Mac OS X, March 24, 2006
  • Mac OS X 10.5 Leopard, October 28, 2007
  • Mac OS X 10.4 Tiger, April 28, 2005
  • Mac OS X 10.3 Panther, November 9, 2003
  • Mac OS X 10.2 Jaguar, September 5, 2002
  • Mac OS X 10.1 (Puma), October 15, 2001
  • Mac OS X 10.0 (Cheetah), April 2, 2001
  • Mac OS X Public Beta, October 3, 2000
  • Mac OS X Q & A, June 20, 2000
  • Mac OS X DP4, May 24, 2000
  • Mac OS X DP3: crucible by Water, February 28, 2000
  • Mac OS X Update: Quartz & Aqua, January 17, 2000
  • Mac OS X DP2, December 14, 1999

  • Apple reveals Mac OS X Lion, Server prices for traffic and education | killexams.com actual questions and Pass4sure dumps

      Apple has announced prices and deployment plans for its education and traffic customers installing Mac OS X and Mac OS X Server, with licenses starting at $29.99 in volume.The company has published a PDF document that reiterates that consumers will install Lion via the Mac App Store as a $29.99 download that may live installed on any Mac connected to the iTunes account used to download it.

    For traffic customers, Apple's online traffic Store will tender volume licenses at the very $29.99 cost in a minimum quantity of 20 licenses. The company will besides tender maintenance contracts for $49.99 per license at the very minimum quantity.

    Education customers can buy Lion via the Apple Education Licensing Program or the online Education Store. The current OS will live packaged with iLife and iWork apps in a "Apple Software Collection" bundle priced at $39 per machine in volume packs of 25 licenses.

    Apple notes that the current OS minimally requires a Mac with a Core 2 Duo; Core i3, i5 or i7; or Xeon CPU and at least 2GB of RAM, and must live running Mac OS X Snow Leopard 10.6.6 or later. This excludes 32-bit Core Duo and Core Solo Macs introduced in 2006.

    The company regularly (but not consistently) refers to its current OS in the document as "OS X," dropping the "Mac" from its title in most cases while quiet referring to "Mac OS X" when speaking of the OS in universal terms. Apple's online web pages besides commonly now refer to the OS as simply "OS X."

    Lion mass deployment

    Both traffic and education customers will receive a unique Mac App Store redemption code that can live used to download the Lion installer, which can then live used across uncouth licensed machines to deploy the current OS.

    The installer will besides uphold Apple's existing mass deployment techniques, including NetInstall and NetRestore images for distributing the installer and running it in site for unattended, diskless installation, as well as distribution via Apple Remote Desktop for remote mass installations of configured machines.

    The document besides clarifies that subsequent updates for Lion systems will live delivered through Software Update rather than via the Mac App Store, preventing any exigency to manage Apple ID accounts on volume licensed machines.

    Additionally, the company has stated that the current OS will live available as a free update to uncouth customers who buy a current Mac on or after June 6, 2011 when the current OS was formally released. Those customers can request a free Up-To-Date upgrade to obtain Lion on machines that were not bundled with it.

    Mac OS X Server a $49.99 option

    Apple besides announced that Mac OS X Lion Server will live available as a separate $49.99 option for Lion buyers. Existing Snow Leopard Server users will live able to upgrade to Lion Server by buying Lion along with Lion Server, for a total of $80.

    Previously, Mac OS X Snow Leopard Server was priced at $499 for an unlimited client license, although some online retailers discounted the cost down into the ballpark of $390. Prior to Snow Leopard Server, Apple formerly sold Mac OS X Server for $500 in a limited client version and $1000 for an unlimited client license.



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