CP/M-86

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CP/M-86 was a version of the CP/M operating system for the Intel 8086. The commands are those of CP/M-80. It was later reworked to become MS-DOS compatible and renamed to DR-DOS and is discussed at more length in that article.

CP/M 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.

Versions

A given version of CP/M-86 will have two version numbers. One applies to the whole system and is usually displayed at startup; the other applies to the BDOS kernel. Versions known to exist include:

CP/M-86 for the IBM Personal Computer Version 1.0 (BDOS 2.2) - January 1982 - Initial release for the IBM PC.
CP/M-86 for the IBM Personal Computer Version 1.1 (BDOS 2.2) - March 1983 - Hard drive support was added.
Personal CP/M-86 Version 1.0 (BDOS 3.1) - November 1983 - Released for the Siemens PG685. Based on the multitasking Concurrent CP/M kernel, it could run up to four tasks at once.
Personal CP/M-86 Version 3.1 (BDOS 3.3) - January 1985 - A version for the Apricot F-Series computers. This version gained the ability to use MS-DOS formatted disks.
Personal CP/M-86 Version 2.0 (BDOS 4.1) - 1986 or later - Released for the Siemens PC16-20. This is the same BDOS used in DOS Plus.
Personal CP/M-86 Version 2.11 (BDOS 4.1) - 1986 or later - Released for the Siemens PG685.

It is believed that the various Personal CP/M-86 versions were based on an unreleased product known as CP/M-86 Plus; all known Personal CP/M-86 versions contain this string.

External links

[The Unofficial CP/M Website], which has a licence from the copyright holder to distribute original Digital Research software.

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