O is for OS/2. If last week's example (Netscape) showed how to get it right in the computing world, OS/2 is an example of how to miss the mark. An operating system is the background software that makes all the other programs run, and on paper IBM's OS/2 should have been a winner for PCs. The first version, released in 1987, had Microsoft's backing: Bill Gates once said: "OS/2 is the platform of the Nineties." He's changed his mind since. From version 1.3 onwards, OS/2 has been the responsibility of IBM, which has spent $2bn developing it.

The latest incarnation, OS/2 Warp, was released in 1992, and has some very tasty features: multitasking, "multithreading" (letting subtasks run in the background), "plug and play", long file names, and 32-bit programs. It could also run DOS and Windows programs. In short, everything that Windows 95 had much later (and the Macintosh had five years earlier).

Given that that's the case, why is Apple's share of the market only 8 per cent, and OS/2's less than 5 per cent? Because IBM and Apple separately lost their own marketing wars. Apple's problems derive from its refusal to license its operating system. IBM, though, was mad keen to get people to use OS/2, and pushed it for all it was worth.

Unfortunately, "Big Blue" has a history of selling people things cheaply but then leading the buyer down a path where their choice is more and more limited - to IBM. When IBM was trying hardest to push OS/2, Microsoft seemed like a brave independent, rather than a world-dominating giant.

OS/2 has not done badly: around 8 million copies have been sold worldwide, and some market observers reckoned that for the home market in the US, it was outselling Windows 95 last year. But that's for people buying a separate operating system. Go down to a local shop and switch on the nearest PC, and the logo that comes up is very unlikely to be IBM's. Microsoft got in there because it seemed the lesser of two evils to PC manufacturers. IBM might - almost certainly does - have the superior technology with OS/2. But manufacturers were still worried about IBM's past reputation - for once, its dominance in the past has hobbled its future.