Mac OS X Snow Leopard
Interface enhancements like Expose in the Dock and better file and folder viewing in Stacks make finding apps and files much easier. A completely overhauled QuickTime X now sports a cleaner interface and recording tools. The much-anticipated Exchange support across Mail, the Address Book, and iCal is huge for those who take their Macs to work.

New technologies
Apple says a few new technologies in Snow Leopard make it worthy of the upgrade alone, with several features that Apple says will boost performance. Because all new Macs come with 64-bit multicore processors, multiple GBs of RAM, and high-powered graphics processing units, all the major applications in Snow Leopard--including the Finder--have been rewritten in 64-bit to take full advantage of the hardware. (The 64-bit technology allows application developers to allocate more memory to complete tasks so that the software runs faster and more smoothly.)

Apple has also added what it calls the Grand Central Dispatch that manages data sent to multicore processors in an effort to maximize performance; Apple says the GCD will speed up any application task, from processing images in Photoshop to playing your favorite games. The addition of the GCD also takes away the need for software developers to spend as much time managing multicore processors.

Another new technology in Snow Leopard is OpenCL, which allows software developers to tap into the power of any onboard video cards (or GPUs, for graphics processing units) for general-purpose computing without the addition of enormous amounts of code. Like the GCD, these are improvements that will mainly affect software developers. But hopefully it will mean more and better-performing software for users in the future.

• Exchange The biggest new feature in Snow Leopard is support for Exchange, Microsoft’s popular e-mail, contact, and calendar server.
• Malware Check Apple’s not trumpeting the feature, but Snow Leopard does actually include a certain degree of built-in protection against dangerous software.
• Exposé Exposé displays one app's windows, including two minimized ones.
• Dock Snow Leopard brings a few minor improvements to the Dock.
• Finder The Finder, the central point for managing files and folders in Mac OS X, has been completely rewritten in Snow Leopard. But you’d hardly know it from looking.
• Smart Eject If you use external hard drives, thumbdrives, or the like, you’ve probably run into one OS X’s annoyances: sometimes your Mac just loves your external volumes so much that it won't let them go. If you’ve ever tried to eject a volume only to have OS X tell you the volume is in use and can’t be ejected, or if you’ve ever been scolded by OS X for disconnecting a volume that was still mounted, you know what we’re talking about.
• Substitutions Many programs autocorrect what you type, changing teh into the, for example. And a host of Mac utilities will do the trick, too. Now Apple has built autosubstitution of text into OS X. Programs have to be modified to specifically support it; but once they are, they’ll all share the same substitution list, which you can see in the Text tab of the Language & Text pane in System Preferences.
• Services In Snow Leopard, Apple finally cleans up OS X’s Services menu. That menu has been around forever, but its implementation has been surprisingly awkward. To access it, you had to go to the Application -> Services menu.
• QuickTime The new version of Apple’s QuickTime multimedia architecture in Snow Leopard is called QuickTime X.
• Preview Snow Leopard’s Preview app, now at version 5, sports some exceedingly useful fixes and refinements.
• Accessibility Apple has been gradually bringing Mac OS X up to speed in terms of accessibility features for users with physical disabilities.

• Mac computer with an Intel processor (IA-32). "Yonah" processors such as Core Solo and Core Duo can run only 32-bit applications; later x86-64 architecture processors such as Core 2 Duo will also be able to run 64-bit applications.
• 1 GB of RAM
• 5 GB of free disk space
• DVD drive (also accessible via Remote Disc) or external USB or FireWire DVD drive for installation