Microsoft, a leading company by market capitalization, was founded in 1975 by Bill Gates and Paul Allen.
Gates and Allen established Microsoft after developing a version of the BASIC programming language for the Altair 8800, an early personal computer. Their company initially focused on software rather than manufacturing its own computers.
Microsoft's major early breakthrough came when IBM selected Microsoft to provide an operating system for its IBM PC. Microsoft acquired the rights to an operating system called 86-DOS, adapted it, and marketed it as MS-DOS.
Paul Allen left his daily role at Microsoft in 1983 after being diagnosed with Hodgkin lymphoma, although he remained a significant shareholder. Steve Ballmer joined Microsoft in its early years and later became CEO, while Satya Nadella became CEO in 2014.