MS-DOS was a renamed form of 86-DOS [11] – owned by Seattle Computer Products, written by Tim Paterson. Development of 86-DOS took only six weeks, as it was basically a clone of Digital Research\'s CP/M (for 8080/Z80 processors), ported to run on 8086 processors and with two notable differences compared to CP/M; an improved disk sector buffering logic and the introduction of FAT12 instead of the CP/M filesystem. This first version was shipped in August 1980.[5] Microsoft, which needed an operating system for the IBM Personal Computer[7][8] hired Tim Paterson in May 1981 and bought 86-DOS 1.10 for $75,000 in July of the same year. Microsoft kept the version number, but renamed it MS-DOS. They also licensed MS-DOS 1.10/1.14 to IBM, who, in August 1981, offered it as PC DOS 1.0 as one of three operating systems[12] for the IBM 5150, or the IBM PC. MS-DOS 6.x Version 6.0 (Retail) – Online help through QBASIC. Disk compression, upper memory optimization and antivirus included. Version 6.2 – Scandisk as replacement for CHKDSK. Fix serious bugs in DBLSPACE. Version 6.21 (Retail) – Stacker-infringing DBLSPACE removed. Version 6.22 (Retail) – New DRVSPACE compression. Quelle: Wikipedia https://en.wikipedia.org/wiki/MS-DOS