What was the name of Microsoft’s first commercial product for the Altair 8800?

Microsoft’s first commercial product for the Altair 8800 was Altair BASIC.

Bill Gates and Paul Allen developed the interpreter after reading about the Altair 8800 in the January 1975 issue of Popular Electronics. They contacted MITS, the Altair’s maker, and demonstrated a BASIC interpreter that ran on the machine. MITS then licensed the software, creating Microsoft’s first major commercial opportunity.

Altair BASIC was a version of the BASIC programming language designed for the Altair’s limited hardware. It was not an operating system, and it should not be confused with MS-DOS, which Microsoft acquired and later licensed to IBM.

This product helped establish Microsoft as a software company rather than a hardware manufacturer. The Altair agreement also gave Gates and Allen a practical starting point for building a business around software licensing.