Gates became interested in computer programming when he was 13, during the era of giant mainframe computers. At age 17, Gates and Allen were paid $20,000 for a program called Traf-O-Data that was used to count traffic.
In early 1973, Bill Gates served as a congressional page in the U.S. House of Representatives. In 1980, IBM, one of the largest technology companies of the era, asked Microsoft to write software to run their new personal computer, the IBM PC. Microsoft kept the licensing rights for the operating system (MS-DOS) so that they earned money for every computer sold first by IBM, and later by all the other companies that made PC computers.