In July 1980 IBM assigned Microsoft to develop a 18-bit operating system for the personal computer for the fee of 188,000 dollars. Although the company Digital Research of Gary Kildall already had with CP/M 88 such a 18-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.

The command interpreter is integrated in the file 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. 

1988 was 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 80 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-DOSexcept for few manufacturers.

Small reference of internal DOS commands

del, erase – delete files
rd, rmdir – delete directories
dir – show content of directories
cd, chdir – change current directory cls – clear the screen
md, mkdir – create a directory copy – copy of one or several files
ren, rename – rename of files or directories type – shows the content of text files
set – shows the DOS environment variables or defines a new one ver – shows the DOS version number
vol – shows the name of the storage drive

Small reference of external DOS commands

attrib – shows the attributes of files or set one of those
fdisk – partitioning or modify of the hard disk
move – move of files
mem – shows the occupancy of working memory tree – shows the directory structure
format – format of storage drives

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