Mac OS X has been a long time in the making. Until its release, Macintosh users loyal to Apple's OS had to make do with co-operative multi-tasking, instability and a rapidly aging codebase. There had been attempts in the past to modernise the Mac OS, but all were aborted after going through vast amounts of money; obviously, something had to be done, and fast.

In the meantime, a company by the name of Be, Inc had been working on their own PowerPC-compatible operating system, which they had named BeOS. While nowhere near as popular as the Mac OS, it soon found an audience who were happy to install this modern, powerful OS on their Power Macs. As Apple began to search for a successor to the Mac OS, Be's CEO, Jean-Louis Gassée, made his move. He offered to sell Be to Apple for the cool price of $200 million. Gil Amelio, then-CEO of Apple, thought this ridiculous.

Enter Jobs. Steve Jobs 'phoned Amelio, citing his concerns over an acquisition of Be. Soon after, NeXT staff were in contact with their Apple counterparts, hyping NeXT's own operating system, OPENSTEP.

Apple had announced that they were to release their OS strategy by January, 1997; by the time Jobs had rung in November, 1996, time was rapidly running out. Apple had two serious contenders vying to have their technology form part of the next-generation Mac OS: Be and NeXT. While Be were relatively new, and had many areas of their OS yet unfinished (at the time, BeOS did not even ship with printer drivers), Jobs affirmed that OPENSTEP (previously known as NEXTSTEP) was not only mature, but years ahead of the competition.

On December 20th, Apple had made up its mind: it was to buy NeXT, for $427 million. Steve Jobs was coming home.

Mac OS X Server 1.0 Codename: Rhapsody
Mac OS X Server was the first product to be launched using NeXT's technology; in the mean time, Apple had continued to develop the original Mac OS as best it could, releasing what it could of the 'Copland' project as Mac OS 8. The aim was to merge the two company's technologies into one OS, which was code-named 'Rhapsody'.

Rhapsody was almost a preview of what was to come; instead of being for general release, Rhapsody was launched as strictly for servers. While on the surface it appeared to be classic Mac OS, using the 'Platinum' interface which debuted with Copland, it used the NeXT Workspace Manager, used Display Postscript, and featured a proper terminal. Server 1.0 could run applications compiled for it natively, but could also run 'classic' Mac OS applications through the 'blue box' environment - a copy of OS 8 running from within OS X. This would form the basis for the Classic environment in later versions.

Mac OS X Public Beta Codename: Siam
By 2000, Apple had produced a beta of what was to be the first consumer release of their next-gen operating system: Mac OS X. Available to anyone who wanted a copy, for $20, the public beta showed both how far OS X had come since Rhapsody, but also how far it had yet to go; it was buggy and incomplete, and there were many problems people felt were inexcusable, even from a beta. The Apple menu was gone, replaced by an Apple logo in the middle of the menu bar, the Finder was simply called 'Desktop', and many felt the Dock was clumsy, and not a good replacement for the traditional combination of the Apple and application menus.

The new 'Aqua' interface split opinion in two; many thought it to be wonderful, loving the new look, whilst others thought it to be bringing the Mac down to mere eye-candy.

Mac OS X 10.0 Codename: Cheetah
Mac OS X was, at last, officially launched on the 24th March, 2001, having been continually tweaked and modified by Apple. The Apple menu had moved back to the top-left, and was a menu again - although not at all like the classic Mac OS's version. The OS X Apple menu now provided a means of accessing commands such as Shut Down, Restart, and Force Quit, as well as allowing users to quickly access Software Update or change their location. (The classic "About this Mac" is probably the only entry to have survived the transition, as it proudly sits atop the menu.) Also changed from the Public Beta was the Desktop: after outcry from the Mac community, it was renamed back to Finder.

There were, as with most OS releases, few applications available at launch that would run natively; for old software, Classic had to be run, which led to some problems. Despite running Mac OS 9 within OS X, incompatibilities often arose as many programs assumed they had direct hardware access. Classic also had to be launched freshly the first time on each boot the user wanted to run a legacy application; this led to essentally two boot times, which some saw as unnecessary. The OS also lacked any support for playing DVD movies..

The biggest problem with Cheetah, despite its name, was that it simply wasn't as fast as Mac OS 9. The interface was lovely, yet took a large amount of CPU time for itself, leaving many happy to stick with Apple's older OS until things improved. 10.0 was a start, but it was clear OS X simply wasn't quite ready yet.

Mac OS X 10.1 Codename: Puma
Less than a year after 10.0 was available, Apple released a follow-up: Mac OS X 10.1. This was available as an update CD from Apple Stores, or for $20 from Apple via their Up-To-Date program, although it could not be downloaded. It was a well-needed update that, to many Mac users, represents the first 'complete' release of OS X. Puma brought an all-round speed increase to Aqua; it wasn't OS 9 speed, but it was definately welcome. 10.1 also saw the introduction of Mac OS X DVD playback, and introduced a vast number of new printer drivers. As if this wasn't enough, OS X's already good OpenGL implementation was given a shot in the arm.

Mac OS X 10.2 Jaguar Codename: Jaguar
For the first time, a release of Mac OS X was being sold with its codename being part of its official name. Jaguar leapt onto shop shelves sporting a furry X logo, and was to prove an almost necessary update itself. For $129, Jaguar brought another speed bump to Macs running it, featuring many new components such as Quartz Extreme, which offloaded many visual tasks from the CPU onto a compatible GPU, if present. iChat, an AIM-compatible chat program, made its debut, alongside Sherlock 3, searching built into every Finder window, and a new method of zero-config networking: Rendezvous.

Jaguar allowed Macs running Mac OS X to become wireless base stations, a feature inherited from the classic Mac OS, as well as allowing it to become an SMB server. Support for Microsoft Active Directory was also added, rounding off this major set of improvements. Jaguar was more than a service pack - it was what OS X should have been all along.

Mac OS X 10.3 Panther Codename: Panther
The fourth release of Mac OS X was again released with its codename intact, and Panther mimicked its forebear with yet another round of speed boosts. By this point, OS X was running not just well, but very well, even on hardware as old as the original iBook. Panther brought a new visual style to the Mac OS with its brushed metal interface, first seen in QuickTime and iTunes, which it applied to the iApps - and the Finder! For those who didn't like this new look, it could be removed from the finder, at the cost of the toolbars - brushed metal, it would appear, is the new black. Brushed metal or not, another departure from the old school of Apple design is the loss of the pinstripes in the title bars of windows.

Replacing part of the Finder's toolbar at the top of each window is the new 'Places' sidebar. This holds quick links to devices and folders, fully customisable like the Dock. This is a quick and easy method of moving files around, as it is fully drag-and-dropable, and the user can put just about anything he or she wishes to on it. (Apparently, it was inspired by the iTunes playlist bar.) The Finder's search bar now searches in real time, providing the ability to hunt down documents with speeds that wouldn't be bettered until something a little later to come.

The visual abilities of Panther are striking, most notable of all being Exposé. With the touch of a button, all windows shrink down on-screen - you can just click on the one you wish to view, and there it is. Touch another, and only the current application's windows appear. And to top this all off, a third key will banish all windows from the screen, leaving only the desktop. Want to get back to where you left off? Just tap the key again. (Exposé can, with typical Apple thought, be made into a slick slow-motion effect by holding down Shift. This works for maximising and minimising windows, too, as it has done since 10.0) Apple's next most striking visual trick is Fast User Switching. Windows XP has this, but not on this scale - the entire display rotates, forming a cube with two users' desktops on the two visible faces, rotating to the user you switch to. Very swish.

Mac OS X 10.4 Tiger Codename: Tiger
The current, and only-just released version of Mac OS X has been hyped as having over 200 new features, but three of them immediately rise to prominance: Spotlight, Automator and Dashboard. Spotlight is a completely new search system, being available throughout the OS through an icon in the menu bar. Searches happen as you type, with results appearing nigh-on instantly. Searches pour through metadata. The whole system is indexed and searchable - the idea being, if you can describe it, Spotlight can find it. With importers becoming available for more file formats, expect to be able to find whatever you want, whenever you need it.

Automator expands on the highly-popular AppleScript by introducing an easy-to-use, intuitive interface for it. It allows you to build workflows of actions to be performed sequentially, so if you really want to open a web page in Safari, download all the pictures, zip them then email that archive, you can - all from within Automator. This has the potential to make time-consuming exercises ludicrously easy - and if you want to expand even further, you always have AppleScript.

Dashboard has taken a lot of flak for its similarity to a third-party application called Konfabulator. In response, its developers have ported it to Windows; Apple claim that Dashboard is simply a continuation of their old desk accessories. So what is Dashboard? Put simply, it is an Exposé-like method for gaining quick access to what Apple call 'widgets' - small mini-applications that you can drag onto your desktop and play with. The best part of this, is that they're only there when you want them to be. Press the Dashboard key, and the rush on-screen; push it again, and away they go.

Under the hood, Tiger provides all manner of improvements, from CoreData and CoreImage, to new graphics capability from Quartz 2D. (For an example of this, on a supported graphics card, Dashboard widgets will leave a ripple effect when they are placed on-screen) As with any OS X release, it feels snappier than the previous version, and there are plenty of changes that the casual user is unlikely to ever find out about or even know of. They do their job quite invisibly and happily.

Mac OS X 10.5 Codename: Leopard
At the 2005 WWDC, Steve Jobs dropped several bombshells: Apple would be switching to Intel processors for the Macintosh. This is the 'third transition' as he termed it; Apple had already made two, firstly from 68k to PowerPC processors in the early 90s, and from Mac OS 9 to Mac OS X. Part of this transition would be a version of Mac OS X which ran on Intel.

This is where Jobs revealed what many had speculated for some time: Apple had, since the first test builds of OS X, been maintaining an Intel-based port. Come the close of 2006, Apple intend to have their sixth major release of OS X available on both Intel and PPC platforms. This sixth release is currently code-named Leopard. With the first Intel-based Macs available as of January 2006, however, currently an Intel version of Tiger is shipping. On the surface, and in general use, it is identical to the PowerPC version, however it includes an important addition: a translation layer named Rosetta.

Rosetta transparently allows PowerPC binaries to run on Intel Macintoshes; while this comes at a performance hit, the result is much like the 68k to PPC transition of earlier. Even AltiVec is translated; however, further breaking with the old Mac OS, Classic support has finally been dropped.

So with Classic finally dropped, what does Leopard bring to the table? A number of new features have been added, with some of the more important representing significant changes in the way we use our Mac. Quick Look, for example, allows the user to preview almost any file simply by tapping the space bar from within the Finder. MP3s spring to life and play without needing to wait for iTunes or QuickTime, Word documents can be scrolled through and read, pictures display, all within just a few seconds even on a lowly G4.

Spaces joins Dashboard and Exposé as a function key-triggered feature, bringing official multiple desktop support to Mac OS X. One can pin applications to different spaces, switching to that space automatically when the application is in focus, and can drag windows to and from at will. Activating Spaces from the Dock or a function key zooms out just like Exposé, showing all spaces with all active windows updating in realtime - even QuickTime videos continue to play, just as with Exposé. One can also jump to a specific space through a key combination or through a menu bar item.

It is Time Machine, however, which for many users was the Next Big Thing. Once an additional hard drive is attached (internal or external, over either SCSI, parallel ATA, SATA, FireWire, USB, or over AirPort via Apple's Time Capsule), it can be selected as a Time Machine volume, with automatic backups being taken every so often. Lost a file, or want to see what it looked like a few days ago? Trigger Time Machine, and a slick (if totally nonstandard) UI floats in, allowing you to pick from all available backups of the current file.

Mac OS X 10.6 Codename: Snow Leopard
2008's WWDC rolled along, and with it Jobs announced the next major release of Mac OS X. Declaring that this was not to be a release full of new features, he instead announced that it would be targeted towards shipping a leaner, more secure, and faster OS than Leopard, promising a significantly reduced disk footprint. Few concrete specifications have been announced, but support for OpenCL should allow for easy development for applications harnessing a video card's GPU, while 'Grand Central' promises to "make it much easier for developers to create programs that squeeze every last drop of power from multicore systems" ( A new version of Safari has also been promised, with a new JavaScript rendering engine as has currently been previewed in the WebKit nightly builds.

What does this mean for the end user? At the moment, not much. Although developer builds have been issued - at present, Intel-only - it is not known whether 10.6 will be released for the PowerPC. Nor is it yet known whether this will be a full-price release, or if it will instead be a free offering á la 10.1.