Yeah, that was Paul Allen not Gates, and he wrote the bootloader on the plane. The interpreter was already finished.
Only full on Gates program I've ever heard of is Donkey.bas
Only full on Gates program I've ever heard of is Donkey.bas
Gates was responsible for writing the first Altair Microsoft BASIC interpreter, except the bootloader, the software for the Kyotronic clones (designed in collaboration with Kay Nishi and licenced to Kyocera, Tandy and others).
Gates also had ample experience in programming minicomputers such as DEC PDP series together with Paul Allen.
You can read all about it in all the Bill Gates biographies out there.