An Internet Archive user with the nickname f15sim found and uploaded to the Web the oldest version of the 86-DOS operating system, the one that was later bought by Microsoft and turned into MS-DOS, the world’s most widely used operating system for the next 15 years.

86-DOS is a renamed QDOS (Quick and Dirty Operating System) from Seattle Computer Products. The operating system was created in 1980 by 24-year-old programmer Tim Paterson as a version of Digital Research’s CP/M (Control Program/Monitor) operating system for 8086 processors.

86-DOS

The 86-DOS Version 0.1-C with the serial number #11, on an original seemingly still 8-inch floppy disk from 1980, was found by an Internet archivist. You can even download it and try to run it on the appropriate hardware.

In May 1981, Microsoft acquired the rights to 86-DOS 1.10 and hired Tim Paterson to develop an OS for future IBM PC computers. On August 12, 1981, IBM PCs were presented to the public with support for three operating systems: CP/M-86, UCSD p-System, and IBM PC DOS. Actually, IBM PC DOS is IBM’s version of 86-DOS. Later, Microsoft started its own distribution of the OS called MS-DOS.

The latest version of IBM PC DOS 7.1 was released in 2003, MS-DOS 8.0, which was already part of Windows Me, in 2000. There is still a free FreeDOS, the latest version of which, FreeDOS 1.3, was released on February 20, 2022.