Microsoft signs deal with IBM – November 1980

On November 6, 1980 – Microsoft signs the contract with IBM to create a new operating system (MS-DOS) for the IBM-PC.  Microsoft co-founders Bill Gates and Paul Allen developed the Microsoft Disk Operating System existing software from a Seattle company as a foundation.   The Operating system was a thought to be a direct copy of Gary Kildall’s CP/M however with the addition of third party programs, the DOS package was considered unique enough to prevent Microsoft from being sued by Kildall or Digital Reasearch.    IBM eventually included options for users to use MS-DOS or CP/M however the cost for CP/M was Microsoft become the default operating system of choice for most users.