How msdos was developed?
MS-DOS short for Microsoft Disk Operating System) is an operating system commercialized by Microsoft. It was the most commonly used member of the DOS family of operating systems and was the main operating system for personal computers during the 1980s. It was preceded by M-DOS (also called MIDAS), designed and copyrighted by Microsoft in 1979. MSDOS was based on the Intel 8086 family of microprocessors, particularly the IBM PC and compatibles. It was gradually replaced on consumer desktop computers by operating systems offering a graphical user interface (GUI), in particular by various generations of the Microsoft Windows operating system. MS-DOS was known before as QDOS (Quick and Dirty Operating System) and 86-DOS.[
This is quite complicated; Microsoft developed PC-DOS for IBM in 1981 and shortly afterwards started selling MS-DOS - which was a different product - to other companies. However, as time passed "IBM PC Compatibility" became an important selling point and in 1987 MS-DOS and PC-DOS were essentially the same product.
The program segment prefix (PSP) in MSDOS is the first 256 bytes of memory allocated by the command interpreter to load and run a program. The program itself is loaded next. The first 128 bytes of the PSP contains various structures and pointers. The second 128 bytes of the PSP initially contain the command line, and is then available as the default disk buffer for subsequent I/O.
MS-DOS was based upon 86-DOS by Seatle Computer Works. When IBM developed their first PC, they approach Microsoft to write the operating system; at that time, Microsoft wrote computer applications and, in particular, languages - MSBASIC was the industry standard - and didn't have an operating system. Bill Gates realised the opportunity and bought the rights to 86-DOS which was renamed MS-DOS to supply for the IBM-PC.