This week sees the 30th "birthday" of Microsoft's MS-DOS operating system for PCs. Initially "quick and dirty," it soon became merely dirty. Tech Voyage wishes Bill & Co. many happy returns.
On 27 July 1981, Microsoft gave the name MS-DOS to the operating system it acquired on that day from Seattle Computer Products (SCP). The company had planned to use Digital Research's CP/M-86 operating system, which was still in development at that time but SCP decided it had to create its own OS for the card. 
The picture we have today is muddied by the claims that IBM originally wanted to use CP/M-86. IBM and DR famously failed to come to terms and IBM turned to Microsoft for an alternative [which paid] $25,000 for the privilege. By July 1981, Microsoft had sufficient understanding of IBM's plans to consider not merely licensing 86-DOS but buying it outright from SCP, for a further $50,000 in total, $180,000 in today's money.
Today, MS-DOS is rarely used for desktop computing. Since the release of Windows 95, it was integrated as a full product used for bootstrapping and troubleshooting, and no longer released as a standalone product.
But we all know the modern PCs grew so rapidly only after the launch of MS DOS and today it completes its 30th birth day and we wish the MS Team, many happy returns of the day.