Cast your mind back 20 years - if you're old enough. Charles and Diana are walking up the aisle, Ian Botham is single-handedly routing the Aussies, the airwaves rock to the sound of Shakin' Stevens' Green Door. And the IBM PC is born.

It may be difficult for you to believe, but there was a time when an IBM-compatible PC was worth owning. Back when every woman and her dog was trying to imitate Di's hairdo, it was cool to even know what an IBM PC was.

While today most families would list a PC as a standard household commodity, along with their dishwasher, widescreen digital TV and toilet bleach, in the early 80s the IBM-compatible PC was a technological luxury, and getting one required a whopping great chunk of disposable income (around £2,000).

Big blueprint
It was also fairly primitive. The sharp graphics, multitasking apps and networking capabilities of today's gigahertz-plus systems seem a far cry from the PCs of yore. Yet, at the heart of every 21st century Windows-based computer lies an IBM PC.

So why was Big Blue's PC such a hit? For a start, it was a well-designed, well-built machine from a name that businesses knew and trusted. "No one ever got fired for buying IBM," the saying went. And the IBM PC was quickly supported by a host of third-party applications, such as word processors (MicroPro's WordStar, SSI's WordPerfect, among others).

Then Peter Norton developed Norton Utilities to restore a file that he'd accidentally deleted on his own system. And Andrew Fluegelman invented PC-Talk, a program that made it easier for modem users to dial into services such as CompuServe.

Now IBM thought it had a cunning plan: it wanted other companies to supply a broad selection of peripherals for its design, so it made the PC an open, well-documented system. That way it could create a standard for both business and the home, with the IBM PC at the centre. Well, it got the peripherals it wanted, but it also got something else: clones.

In 1982, a startup called Compaq released a 'portable', sewing machine-size computer that worked with software and add-in cards that were designed for IBM's PC. This was possible because IBM had used off-the-shelf parts. Any company could buy an Intel CPU and a Microsoft operating system.

Inside Intel, and the rest as well
IBM's lead slipped in 1986, when Compaq shipped the first PC based on Intel's 32bit 80386
(or 386 for short). As a chip, the 386 was a landmark that made today's windowing, multitasking environments possible. This was the latest, greatest PC of the time – and it wasn't from IBM.

But it still ran MS-DOS, the first big operating system, made to measure for the IBM-compatible PC. In fact, most PCs are still running MS-DOS; it's just not visible. Only with the inevitable triumph of Windows XP – due out in October – will MS-DOS finally be laid to rest.

The secret of the PC's longevity lies in its sheer versatility. Other platforms such as Linux and the Macintosh, which are often praised for superior stability, don't offer anywhere near the flexibility, or indeed the success of a Windows PC.

It may not be perfect, nor is it the market king – but the humble PC did change the course of history. So just for this one month, on its 20th anniversary, please have a little respect. Let's hear it for the IBM-compatible PC.