25th Anniversary of the Personal Computer" 4203

Philip Homburg

This is quite true.

While the original IBM PC was provided with 128 K of memory, and had an 8-bit data bus, it still had a 20-bit address space, and could be brought up to 640 K of memory with suitable memory boards.

It had an operating system which resembled CP-M in many respects, if it at least replaced the "PIP" command, copied from DEC operating systems, with the more comprehensible "COPY".

But the fact of a 16-bit CPU with an address space that went beyond 64 K meant it was a more powerful system. It was 'underwhelming', I suppose, in that there were already more powerful 'true' 16-bit systems at the time, based on the Z-8000 or the 68000 or even the 8086... but these tended to sell for $10,000 or thereabouts.

The IBM PC was entry-level 16-bit computing at a price only slightly above that of an office CP-M system. And the 8-bit market was *heavily fragmented*; CP-M was *sort of* a standard, but different CP-M machines had different floppy disk formats in some cases, as well as many other incompatibilities. And these were office-only systems; people played games at home on Commodore 64s or Atari 800s or Radio Shack Color Computers.

The closest thing to a system that could be used for work *or* play was the relatively expensive Apple II computer. Since it was a 6502 machine, costing much more than, say, a Commodore 64, the fact that it was the 'standard' was less appealing. There were clones - but their legal status was dubious at best. Unlike the Apple II, the higher price of the PC offered clear value in the form of more memory expandability.

The "magic three letters" did offer hope that this machine would be *a standard*, for which a wide variety of third-party software would be available, and that newer machines which were more powerful due to continued improvements in technology would be upwards-compatible, letting one upgrade one's computer without throwing out all one's software.

I'd say that the IBM PC kept that promise. What worked on the PC still worked on the AT, and even on 386 systems, for the most part. Once Windows 95 meant that computers no longer booted into DOS, of course, the platform has changed somewhat.

John Savard