SCO v. IBM reopened

Posted Jun 18, 2013 14:49 UTC (Tue) by anselm (subscriber, #2796)
In reply to: SCO v. IBM reopened by pboddie
Parent article: SCO v. IBM reopened

MS-DOS started out as a »clone«, or, more exactly, a reimplementation of CP/M for the 8088 processor. (CP/M was originally for the 8080/Z80 series of 8-bit microprocessors.) This actually made reasonable sense at the time since the 8088 assembly language was close enough to that of the Z80 to allow for automatic transliteration of existing (Z80) CP/M programs to 8088 assembly; the only thing needed was a way of making the system calls work, and that was exactly what MS-DOS provided.

Various advanced features like a hierarchical directory scheme and stream-oriented IO (both arguably inspired by Unix) only came along with MS-DOS 2, which is why many software packages at the time stipulated a minimum requirement of »MS-DOS 2.11«. This is why we have »\« as a path separator on MS-DOS/Windows, since »/« was already spoken for through MS-DOS's heritage from CP/M (and further back to the DEC operating systems that inspired CP/M).

Digital Research (the company behind CP/M) actually came out with a version for the 8088 and 8086 processors called CP/M-86, but that never really went anywhere because of the success of the IBM PC (with PC-DOS a.k.a. MS-DOS). There were various 808x-based computers in the 1980s that weren't actually compatible to the IBM PC, and these generally used MS-DOS (rather than »PC-DOS«, which was the same but for the IBM PC) or CP/M-86, among other less important operating systems.

SCO v. IBM reopened

Posted Jun 18, 2013 16:34 UTC (Tue) by pboddie (guest, #50784) [Link]

Indeed, the origins of MS-DOS are no longer in dispute.

I'm sure you have more hands-on familiarity with CP/M and DOS (from different vendors), whereas my experiences were with other microcomputer operating systems, but it's interesting to note that it was Digital Research DOS Plus that was shipped on the Amstrad PC1512 (which was rather successful in the UK and Europe), and Concurrent DOS was also offered for some systems.

Certainly, Digital Research were a viable competitor to Microsoft in a market that itself had only developed because of cloning of the original hardware platform.