An extremely brief overview of where the industry is today, and some judgements on its stability.
Until ~1986, IBM pretty much controlled the computer industry. They gradually rolled out technical improvements ... 15% every two years was a figure I remember.
In 1983 IBM came up with the IBM PC and the world changed. They were still however highly influential. Their original architecture was updated in ~1985 with the PC-AT, providing a 16-bit bus. This then became the defacto standard, and many 3rd party manufacturers began building large businesses.
In 1986, IBM introduced the PS/2 with its 32-bit MCA architecture, but the world did not bite! The 16-bit standard prevailed and IBM had lost control of the market. The restrictions of the previous architecture that IBM had designed in prevailed for another 5-6 years.
The truth is probably pretty murky now, but I like the story that a simple operating system - QDOS (Quick and Dirty Operating System) - was bought for $20k and renamed DOS, with Dirty changed to Disk of course.
Bill Gates by all accounts attempted repeatedly to license the Apple OS, but was refused - a true tragedy for all.
Since then Microsoft has been a marketing, if not a technical, triumph.
Until a year or so, the Microsoft hold on games PCs pretty much tied most families into MSDOS, Windows and its derivatives, as it was gaming that lead the technical developments. The DirectX initiative provided them with a good idea so far as games producers were concerned, but also allowed them to move the target for rival platform providers.
This may be about to change tho'. The number one application for home use at present is probably internet and email. And users are demanding more reliable platforms. Unless Microsoft can make a success of their .Net initiatives and tie users more tightly into their technology, there is a real possibility that Linux could make catastrophic gains into their user base.
The day is very close when a PC user will be able to slot in a Linux CD and replace their existing Windows system, and in a painless enough way that the journalists will start to recommend they do so.
Apple have threatened to disappear altogether several times now, but they are still around and in Mac OSX have finally a decent OS to underpin their user centred technology.
Such a shame they did not license the Macintosh OS in 1984.
Such a shame they did not properly develop AUX back in 1987.
A point missed by many is that Apple is now working closer with the Linux open source community. Their new browser Safari is derived from the KDE browser, and you can now run a version of X11 that allows access to many freely available Linux applications - for example Open Office, that can read and edit Microsoft Office documents.