'We coded day and night for the two months to create the software we had said already existed': The history of Microsoft reminds me how far we've come in just 50 years

Mostly? What really sent me down a rabbit hole in reading this code was the syntax:

• The == assignment
• The argument lists <...>
• PRINTX instructions, etc.

The Altair 8800 uses an Intel 8080 processor. This syntax doesn't match the instruction set for Altair or Intel, or even PDP-10 for that matter.

We have some hints about what may have happened. We know that Paul Allen wrote an Intel 8080 emulator designed to translate instructions to ones that a PDP-10 would understand.

We also know that Microsoft later released Macro-80 (M80) Assembly for Intel 8080 and Z80 architectures five years later. It turns out that M80 has <...> argument lists and .printx instructions.

So my suspicion is that Allen built some macro convenience functionality into his emulator, and that the language used is 95% Altair assembly with some macro functionality to support different kinds of Altair configurations and simplify some of the programming. Then they later evolved that into its own product offering and added Z80 support for it as well.

Building a Basic interpreter on top of a custom CPU emulator in a slightly-customized version of assembly in two months between 2.5 people and having it work correctly the first time on untested hardware is pretty damn impressive, whatever you think of Gates. It's no wonder he's so proud of it.