The oldest known version of MS-DOS has been detected and loaded

Microsoft's MS-DOS (and its IBM-branded counterpart, PC DOS) eventually became a software behemoth, powering the vast majority of computers throughout the 1980s and serving as the basis for Windows throughout the 1990s.

But the program had humble beginnings, as we detail in our history of the IBM PC and elsewhere. It started out in the mid-1980s as QDOS, or “Quick and Dirty Operating System,” the work of developer Tim Patterson at a company called Seattle Computer Products (SCP). It was later renamed 86-DOS, after the Intel 8086 processor, and this was the version that Microsoft eventually licensed and purchased.

Last week, Internet Archive user f15sim Find and upload a new old version of 86-DOS to the Internet Archive. Version 0.1-C of 86-DOS is Available for download here It can be run using SIMH emulator; Before that, the oldest existing version of 86-DOS was 86-DOS Version 0.34also raised by f15sim.

This version of 86-DOS is primitive even by the standards of DOS builds of the early 1980s and includes a few utilities, a text chess game, and documentation for said chess game. But early on, it remained primarily recognizable as the DOS that would go on to take over the entire PC business. If you're just interested in screenshots, some have been posted by user NTDEV on The site that was previously Twitter.

According to the release date Available on Wikipedia, this 86-DOS release dates from approximately August 1980, shortly after the “QDOS” moniker was lost. By late 1980, SCP was sharing version 0.3x of the software with Microsoft, and by early 1981, it was developed as the primary operating system for the then-secret IBM PC. By mid-1981, about a year after 86-DOS began operating under the name QDOS, Microsoft purchased the entire program and renamed it MS-DOS.

Microsoft and IBM continued to collaborate on the development of MS-DOS for many years; The version that IBM licensed and sold on its computers was called PC DOS, although the two products were identical for most of their history. Microsoft also retained the ability to license the software to other computer manufacturers such as MS-DOS, which contributed to the emergence of a market for mostly interoperable personal computer clones. The PC market as we know it today still looks somewhat similar to the PC market of the mid-to-late 1980s, albeit with significantly faster and more capable components.