MS-DOS turns 30

Microsoft's DOS, or Disk Operating System – the precursor to the company's Windows operating system, turned 30 years old on Wednesday.

Microsoft acquired the rights to the then fledgling operating system in January 1981 from Seattle Computer Company for what ended up being a final cost of $1m by July 27 1981. By 1995, almost all personal computers used a version of MS-DOS, and it was finally unseated as the world's most popular operating system when sales of Windows 95 and subsequent versions of Windows went on to replace it.

MS-DOS first appeared on IBM’s Personal Computer, or IBM PC, and became the standard operating system by August 1981. Every personal computer application created between 1981 and 1995 was compatible with Microsoft's operating system. Popular software titles at the time included Lotus 1-2-3, an early and popular spreadsheet application that is credited with the success of the IBM PC; WordPrefect, a popular word processor; dBase, a widely-used personal database system, and Borland’s Integrated Development Environment, used by developers to create applications in programming languages like Turbo Pascal and Turbo Basic.

As computer hardware changed in response to users' more demanding needs, MS-DOS' limitations quickly became apparent. The most important limitation was that it could only access 1Mb of the computer's memory, with only 640Kb available to the end user. The limitation was based on the now infamous assumption, made by Bill Gates, that "640K ought to be enough for anybody". The limitation was addressed using various techniques, referred to as expanded memory and extended memory, which were eventually corrected once Intel’s 80386 processor was introduced and came into broader worldwide use in personal computers. Other limitations included upper limits on accessible hard drive storage space and limited file naming capabilities.

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