Also, I went through my box of old software....I still have DOS 1.2, and the first game I remember for the PC...Decathlon. Sigh. Times are a changing. ;)
And how about CP/M, which had the *largest base of installed software* of anyone, of which people thought no one could displace...
CP/M
http://en.wikipedia.org/wiki/CP/M
By Digital Research and Gary Kildall...
Digital Research
http://en.wikipedia.org/wiki/Digital_Research
Gary Kildall
http://en.wikipedia.org/wiki/Gary_Kildall