Apple Inc launched a new version of its operating system for Mac computers on Friday.

Snow Leopard is a relatively cheap upgrade, costing US$29 for an individual user who has Leopard, the previous operating system.

A 'family pack' for five users costs US$49.

For Mac owners using the older Tiger operating system, switching to Snow Leopard costs US$169, or US$229 for a family pack.

Snow Leopard is designed for Macs with Intel chips, which Apple started using in early 2006. It will not run on older Macs with the previous PowerPC family of chips.

In an Apple's demonstration of the software to The Associated Press, these were some of the most obvious changes that stood out in Snow Leopard:

The built-in email, calendar and address book applications will support Microsoft Exchange servers, the kind used by most companies. That means it will be easier to get company email without using dedicated programmes like, Entourage or Outlook, which Microsoft is releasing for Macs late next year. However, Snow Leopard supports only the most recent release of Exchange.

Moving the mouse cursor over a programme icon in the 'dock' at the bottom of the screen reveals all the windows open in that programme, tiled side by side. This is an extension of the 'expose' feature, which shows all windows in all programmes side by side.

Right-clicking in a window should bring up more relevant choices, bringing this function closer to its Windows equivalent.

The new standard version of the QuickTime video-playing software will now convert clips for playing on iPhones or iPods, or upload them to YouTube. You will also be able to trim clips. Previously, you had to buy QuickTime Pro to convert videos or fire up the more time- consuming iMovie.

You can make the file thumbnails even bigger, giving you a better idea of the contents of your hard drive at glance.

The operating system is more compact, freeing about seven gigabytes of hard drive space previously claimed by Leopard.

Ejecting disks should be easier. Sometimes, Macs will not let you eject a disk or disconnect a drive because the operating system believes it is reading or writing to it. Apple says Snow Leopard will be better about freeing up the disk, or if it cannot, it will give a reason.

Web browsing and image and document previews should be noticeably faster. This is because more of the software now processes data in 64-bit chunks, twice as big as before. Other applications should benefit from this change as well, once developers start writing them in 64-bit versions.

Developers will also be helped by a new system called Grand Central Dispatch, which makes it easier to take advantage of the multiple 'cores' in today's processors, boosting the speed of heavy-duty applications, like video editing. It will also be easier to take advantage of more system memory.

For most Mac users, Snow Leopard is likely to be a no-brainer upgrade, given the low price. But early upgraders often face minor bugs and installation problems, so unless you are dying for one of the new features, waiting a month or so is a safer course.

- AP