CPM-86
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CP/M-86 was a version of the CP/M operating system made for Intel 8086 CPUs. It was IBM's first choice as OS for the not-yet-released IBM PC. There are two alternative versions of what happened:
- Gary Kildall, owner of Digital Research who developed CP/M, was not present when IBM visited in late 1980 on short notice, and when contacted he indicated he was not interested in developing a 16-bit compiler at the time and IBM was then forced to look elsewhere.
- IBM considered Gary's licencing price too steep and looked elsewhere for a better deal.
IBM then went to Microsoft, who provided them with PC-DOS 1.0. PC-DOS was based on QDOS (Quick and Dirty Operating System) which Microsoft had just bought and hurriedly polished up.
IBM immediately found a large number of bugs in it and had to extensively rewrite it. Compared to CP/M, PC-DOS was primitive:
- No support for fixed disks.
- Filesystem did not support subdirectories.
These were not critical limitations since the original PC had no hard disk anyway, and there was not much need for subdirectories when a floppy disk only held 160 kilobytes. The original IBM PC was not sold bundled with an operating system, and a purchaser was free to buy a copy of CP/M-86 when it became available a few months after the PC's release in August, 1981. However, PC-DOS sold for $60 while CP/M-86 was priced at $240. The large range of CP/M programs were easy to port to CP/M-86 by software companies, but the price difference meant that there was little demand for them.
As a result, CP/M-86 never really got off the ground, appearing on only a relatively few systems in the early 1980s.