Microsoft’s original 1975 product was a version of BASIC written for the Altair 8800 microcomputer.
Bill Gates and Paul Allen developed Altair BASIC after seeing the Altair 8800 announced in Popular Electronics. The interpreter allowed users to write and run programs on a machine that otherwise had very limited software. It became Microsoft’s first commercial product and established the company in the emerging personal-computer industry.
BASIC means Beginner’s All-purpose Symbolic Instruction Code. It was designed to be easier to learn than many earlier programming languages, helping introduce programming to a broad audience. Microsoft later became one of the world’s most valuable companies through Windows, Office, cloud computing, gaming, and enterprise software.
The Altair product was not Windows and was not a complete operating system. It was an interpreter for the BASIC language, supplied on paper tape for the Altair platform.