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QDOS, which stands for "Quick and Dirty Operating System," was a text-based command-line operating system developed in 1980 by Tim Paterson of Seattle Computer Products (SCP). It is most significant as the forerunner of Microsoft's MS-DOS, which would come to dominate the personal computer market.

Key facts about QDOS

Purpose: QDOS was created as a temporary solution to fill a crucial need for an operating system that could run on SCP's new 16-bit Intel 8086 CPU board. It was developed quickly to avoid delays for customers waiting for the official operating system, CP/M-86.

Design influence: Paterson modeled QDOS on the architecture and commands of the popular 8-bit operating system CP/M, but created it from scratch, ensuring it was legally distinct. This made it easy for developers to port existing software, such as WordStar and dBase, to the new 16-bit platform.

Commercial name: After its initial "Quick and Dirty" designation, QDOS was renamed 86-DOS when it was commercially released by SCP in August 1980.

Microsoft's purchase: In 1981, Microsoft purchased the rights to 86-DOS from SCP for a reported $50,000. Microsoft then licensed the renamed and modified system to IBM for its new Personal Computer, where it was called PC DOS. Microsoft sold its own version to other hardware manufacturers as MS-DOS.

Legacy: Due to the IBM PC's immense popularity, MS-DOS became the dominant operating system for personal computers throughout the 1980s and early 1990s. QDOS is therefore considered the direct predecessor of MS-DOS and the foundation of Microsoft's dominance in the operating system market.