Microsoft, which needed an operating system for the then-new Intel 8086 but had none available, hired Tim Paterson in May 1981 and bought 86-DOS 1.10 for $75,000 in July of the same year. They also licensed MS-DOS 1.10/1.14 to IBM, who, in August 1981, offered it as PC DOS 1.0 as the default operating system for the IBM PC. Continue reading for more.