Founder shares 4K Altair BASIC source ahead of 50th anniversary

Microsoft co-founder Bill Gates has shared the 1975 source code for Altair BASIC.

The code was the foundation on which Microsoft was built. Before Windows and before Office, there was a carefully crafted BASIC interpreter designed to fit within the limited resources available on the Altair 8800.

Why an interpreter? Compiling the code and running it all at once was an option, but Gates explained: "We figured the line-by-line approach of an interpreter would be helpful to novice programmers since it would give instant feedback on their code, allowing them to fix any mistakes as they crop up."

Gates and fellow Microsoft co-founder Paul Allen famously spotted the Altair on the cover of the January 1975 issue of Popular Mechanics. The duo reckoned – correctly as it turned out – that the PC revolution was imminent, "and we wanted to get in on the ground floor."

It took two months to create ...