What was the first product sold by Microsoft?

The first product sold by Microsoft was Altair BASIC, a programming-language interpreter created for the MITS Altair 8800.

The story began after the Altair 8800 appeared on the cover of Popular Electronics in January 1975. Bill Gates and Paul Allen recognized that the new microcomputer needed software and offered MITS a BASIC interpreter, even though they had not yet seen the machine. Allen built an Altair simulator on a PDP-10, allowing the pair to develop and test the program remotely. Monte Davidoff contributed its floating-point arithmetic routines.

MITS licensed the interpreter and distributed it as Altair BASIC. Version 2.0 officially shipped in July 1975 in 4K and 8K editions. The product helped establish Microsoft’s original business model: creating and licensing software for many different computer manufacturers.

A common mix-up is naming MS-DOS or Windows. Both became vastly more influential, but they came later: Microsoft licensed 86-DOS for IBM’s PC in 1981 and released Windows in 1985. Altair BASIC was the small, pioneering product that came first.