Altair Basic was developed by Gates, fellow Microsoft co-founder Paul Allen, and programmer Monte Davidoff. The trio reportedly coded “day and night for two months” in 1975.

BASIC running on this operating system allowed colleges, high schools, and individuals across the country to dial into mainframe computers and write programs using the language.

While remembering a Kodak moment of holding a foot-long piece of paper featuring the code, Gates indicated that Altair BASIC was inspired by the January 1975 copy of "Popular Electronics" magazine.