Assembler programming wasn't an unusually exotic skill in the early 70s, and the PDP-10 was an unusually friendly environment for it. Compared to modern progra

Assembler programming wasn't an unusually exotic skill in the early 70s, and the PDP-10 was an unusually friendly environment for it. Compared to modern programming, assembler on a 16- or 36-bit machine is simple, logical, and not at all abstract. DEC made a point of offering high quality detailed docs to students, and there was a kind of assembler culture that produced operating systems like TOPS-10, compilers for various languages, and editing tools, often with access to the sources. And as others have pointed out, the 8080 was not a complex processor. So mapping its instructions to macros wasn't hugely challenging. I had a friend who wrote a Z80 emulator - a harder challenge - on a PDP-10 as a spare time hobby project. It took about a month of after-hours programming. Full-time, it would have taken much less. More interesting is that it's possible Gates & Allen had access to the sources for the PDP-11 4K word Dartmouth BASIC. I have no idea if the original 8-bit MS-BASIC was a clean room reimplementation. But it's at least possible it wasn't.