What was the name of Microsoft's first product?

Microsoft’s first product was Altair BASIC, a BASIC interpreter created for the MITS Altair 8800 microcomputer. It gave Bill Gates and Paul Allen their first major commercial breakthrough in 1975.

The opportunity began when Gates and Allen read about the Altair 8800 in the January 1975 issue of Popular Electronics. They contacted MITS and offered to demonstrate a BASIC interpreter, even though they did not yet have a finished version or an Altair machine. Allen built an emulator on a PDP-10, while Gates and Monte Davidoff worked on the interpreter and its floating-point mathematics.

Their demonstration succeeded, and MITS agreed to distribute the software as Altair BASIC. Early versions were delivered on paper tape and could run in as little as 4 kilobytes of memory. The product became the foundation of Microsoft’s BASIC licensing business.

MS-DOS, Windows, and Office came much later. MS-DOS became important after Microsoft licensed it for IBM’s 1981 personal computer, while Windows and Office eventually became flagship product families.