Here’s the 50-year-old Microsoft source code that inspired the first Apple computer

Maybe you didn’t realize this, but Microsoft is actually older than Apple. While Apple marked its 49th anniversary earlier this week on April 1, Microsoft will celebrate its 50th anniversary on April 4. To commemorate the event, Microsoft co-founder Bill Gates has posted the source code for Microsoft’s first-ever product, Altair BASIC.

The story of the product begins with the computer credited with starting the personal computer revolution, the MITS Altair 8800. (Yeah yeah yeah, I know what you’re thinking, “What about the Apple II? I thought this was Macworld!” Even PCWorld said it’s the greatest PC of all time!) But the Altair 8800 has a unique place in history. When it was featured on the cover of the January 1975 issue of Popular Electronics, enthusiasts everywhere were excited about its potential, including Bill Gates and Paul Allen, then students at Harvard.

Gates and Allen thought that the Altair 8800 was a sign that the “PC revolution was imminent,” as Gates puts it. They decided to create a version of BASIC that can run on the Altair–BASIC, for you young whippersnappers who pay too much attention to those darn TokToks or whatever you call ’em, is a computer language designed for people with, in Gates’s words, “no computer experience.” BASIC on an Altair 8800 would widen the device’s market and bring personal computing one step closer to the masses.

Gates details some of the things they had to do to make Altair BASIC a real product, including not having actual access to the Intel 8080 chip that was in the Altair 8800, how to handle memory limitations (you thought 8GB was diddly squat, try 256 bytes!), and rushing to make a tight deadline. Eventually, they entered a licensing agreement with MITS, and Micro-Soft (the name originally had a hyphen) was born.

As the story goes, Steve Wozniak saw the Altair 8800 running Gates’ BASIC at a meeting of the Homebrew Electronics Club. However, the Intel chip was too expensive, so he wrote a new version of Gates’ Altair BASIC for the cheaper Motorola 6800 chip, which became the Apple I with the help of a guy named Steve Jobs. A few years later, they released the greatest PC of all time, the Apple II, and well, you probably know the rest. If you don’t, here’s a recap.

But back to Microsoft. The Altair BASIC source code is available as a PDF download, covering 157 pages. Gates is “super proud of how it turned out,” and considering what Altair BASIC led to, he should be. If you are a developer or a computer geek, it’s worth a look. If you’re interested in learning more about Bill Gates before Microsoft, read his autobiography, Source Code: My Beginnings.