Paul and Bill Gates wrote the code that became the first product of their new company, Microsoft, in the 1970s.The code was for an Altair BASIC interpreter, which translated code into instructions line by line.They simulated the Intel 8080 chip to test the software without an actual Altair computer.The source code is available as a scanned PDF, and an annotated disassembly of Altair BASIC 3.2 is on GitHub.