The next version of Mac OS X will go on sale on Friday 26 October, and Apple is already taking pre-orders. That means Mac users finally have a decision to make.

Is a move to Leopard smart? Everyone will have different reasons for considering the switch, but assuming you give Apple a nod and your £85, here are the questions to ponder as you prepare for next Friday. We'll start with the basics first.

What is Leopard?

Leopard is the code name for Mac OS X 10.5, the latest in a string of operating system releases from Apple that go by names from the family Felidae. The current operating system, Version 10.4, is Tiger, which was preceded by Panther, Jaguar, Puma and Cheetah, in reverse order. It is the first major release - in Apple's eyes, that means a shift in numerical nomenclature of one-tenth of a point - since April 2005. It also marks the longest time between releases since Apple started rolling out Mac OS X.

As to why Apple CEO Steve Jobs and company insist on naming their operating systems after cats, you'd have to ask them. But with 41 species altogether in the family, there are enough to keep going for another 43 years or so.

Mac OS X 'Chinese Mountain Cat', anyone?

Why would I want to spend £85 on a new operating system? Tiger is working fine. We're betting you're taking a subtle shot at Windows Vista here. If not, Apple says it has more than 300 reasons for upgrading, citing the number of new features it claims that Leopard has. Many are under the hood and hard to spot for all but the most dedicated - as in the Apple Dictionary, which the company says now includes "a dictionary of Apple terms." Feature or market-speak - you decide. But there are several that make most everyone's justification list, including these five: Time Machine, Boot Camp, Parental Controls, a revamped Desktop and a more powerful Spotlight search.

Whether the changes are worth the £85 is, of course, between you and your bank account.

Will my Mac run Leopard?

Apple has struck some older PowerPC-based Macs from the upgrade list by requiring at least a PowerPC G4 processor running at 867MHz. That means the 800MHz PowerBook G4, 800-MHz iMac G4, 800-MHz iBook G4 and others of their ilk and age are out of luck, officially anyway. All Intel-based Macs are Leopard-ready, however, as are all PowerPC G5 systems.

Leopard's other requirements are 512MB of RAM, 9GB of free space on the hard drive, and a DVD drive.

I've got three Macs at home. Is Apple selling Leopard in a Family Pack?

Yes. Apple is already taking pre-orders for a five-licence edition, priced at £129. Leopard's Family Pack licence sports the same conditions as Tiger's, which means you can install the operating system on up to five Macs in the same household (machines with kids at college count). The Pack is an unbeatable deal: £26 per machine if you have five Macs.