Thirty years ago, on July 27 1981, Microsoft bought the rights for QDOS (Quick and Dirty Operating System) from Seattle Computer Products (SCP) for $25,000. QDOS, otherwise known as 86-DOS, was designed by SCP to run on the Intel 8086 processor, and was originally thrown together in just two months for a 0.1 release in 1980. Meanwhile, IBM had planned on powering its upcoming Personal Computer with an Intel 8086-compatible version of CP/M, which was the standard OS for Intel 8080 and other 8-bit architectures at the time, but a deal could not be struck with CP/M’s developer, Digital Research. IBM then approached Microsoft, which already had a few years of experience under its belt with M-DOS, BASIC, and other important tools — and as you can probably tell from the landscape of the computer world today, the IBM/Microsoft partnership worked out rather well indeed.

IBM released its Personal Computer in August 1981 running version 1.14 of SCP’s QDOS — but a few months later Microsoft produced MS-DOS 1.24, which then became the standard IBM PC operating system. In March 1983, both MS-DOS 2.0 and the IBM PC/XT were released. The rest, as they say, is history. MS-DOS 3.0 followed in 1984 (alongside the IBM PC/AT), and MS-DOS 4.0 with a mouse-powered, menu-driven interface arrived in 1989. It’s around this point that IBM’s PC operating system, PC-DOS, began to diverge from MS-DOS — and of course, come 1990, Microsoft released Windows 3.0, which would change Microsoft’s focus forever. It’s also around this time that developers start to feel the pinch of the 640KB conventional memory limit imposed by IBM’s original hardware specifications.



MS-DOS 2.0 on 5 1/4″ floppies — from Ty’s Hobbies Website

Still, come 1991, MS-DOS 5.0 was released (along with the much-loved QBASIC), and MS-DOS 6.0 with much-maligned DoubleSpace disk compression tool appeared in 1993. By this stage, IBM, Digital Research (DR-DOS), and Microsoft were all leapfrogging each other with different version numbers and features. IBM released PC-DOS 6.1, and MS followed quickly with MS-DOS 6.2. IBM released PC-DOS 6.3 — and Novell trumped them all by releasing Novell DOS 7.0. In 1995, however, Windows 95 with an underpinning of MS-DOS 7.0 and its new FAT32 file system was released, and the history of DOS draws to a close. Every other version of DOS was quickly squished out of existence by Windows 95, and it wouldn’t be until the late 90s and the emergence of the Dot Com Bubble that another command-line OS would yet again rise to prominence in the shape of Linux.

Wikipedia has an excellent account of the history of x86 DOS operating systems, and also a table that compares and contrasts each of the different versions from IBM, MS, Digital Research, and others. If you’re interested in the original development of QDOS, check out its creator’s blog.

Read more about QDOS, CP/M-86, MS-DOS, and the IBM PC