What was the fist mass-produced program written by bill gates company micro soft?

The first mass-produced program written by Microsoft, co-founded by Bill Gates and Paul Allen, was a version of the BASIC programming language for the Altair 8800 microcomputer in 1975. This product marked Microsoft's entry into software development and laid the groundwork for its future success. BASIC became widely adopted and helped establish Microsoft as a key player in the burgeoning personal computer market.