Microsoft to develop a 16-bit operating system for the personal computer for the fee of 186,000 dollars. Although the company Digital Research of Gary Kildall allready had with CP/M 86 such a 16-bit version,but by circumstances no contract has been established with IBM. Microsoft did not have yet any operating system, Microsoft licensed CP/M from Digital Research in November 1977 for 50,000 dollars. Since Microsoft could not sell licenses, a corresponding agreement with the company Seattle Computer Products was reached for QDOS. QDOS is a 16-bit clone of CP/M and was finished by Tim Paterson in April 1980. At first Microsoft licensed QDOS for 25,000 dollars. After a licence agreement with IBM was signed, Bill Gates bought QDOS for 50,000 dollars in July 1981. How proved this was a very lucrative business. IBM delivered it on all IBM computers as PC DOS for the first time on the IBM 5150 PC, for all other ones the name MS-DOS was for OEM partner. MS DOS 1.0 consists of about 4,000 lines assembler code. The command interpreter is integrated in the file command.com with the internal commands for MS-DOS. Together with the file io.sys for simple device routines like the access to the monitor, keyboard, fixed storage disks and interfaces as well as the booting code these form the base operating system. DOS works very hardware near. MS-DOS established and had reached measured on the market share a monopoly in the DOS market. The number of the MS-DOS installations grew worldwide to about 60 million and surpassed all other systems with that amount. Almost every software company offered standard applications like word processing, calculation or also special solutions like measurement tools, CAD (Computer Aided Design) or image processing for MS-DOS. The PC manufacturers designed her systems compatible to MS-DOS except for few manufacturers.