To celebrate Microsoft’s 50th anniversary on April 4, 2025, Bill Gates decided to release something very special: the source code for Altair BASIC. This piece of code marked the beginning of Microsoft’s journey and laid the foundation for the massive software empire it is today.
A Glimpse into the Past: The Birth of Altair BASIC
In his blog post, Bill Gates shared a 157-page document containing the source code of Altair BASIC, a program he wrote back in 1975 using assembly language. The software was inspired by an article in Popular Electronics magazine about the Altair 8800, a microprocessor powered by Intel’s 8080 chip.
At the time, Gates was a freshman at Harvard, and along with his friend Paul Allen, they were fascinated by the idea of the Altair 8800. They saw a chance to make computing more accessible to people by offering a simpler programming language—BASIC—instead of the more complex assembly language.
A Bold Bluff That Led to Success
Gates and Allen weren’t shy about making bold claims. They contacted Ed Roberts, the founder of Micro Instrumentation and Telemetry Systems (MITS), the maker of the Altair 8800. The duo told Roberts they had already created a BASIC interpreter for the Altair 8800, even though they hadn’t actually written any code yet.
But, in true entrepreneurial spirit, they worked tirelessly for the next two months to make their promise a reality. Paul Allen developed a program to simulate the Intel 8080 chip on a PDP-10 mainframe, allowing them to test the software without needing an actual Altair 8800. Meanwhile, Gates focused on writing the code, and their friend Monte Davidoff worked on the math package.
The First Official Microsoft Product
After two months of hard work, Gates and Allen successfully created Altair BASIC. When they presented it to Ed Roberts, MITS agreed to license the software. This was the first official product from Microsoft, which was still called Micro-Soft at the time.
Bill Gates reflected on how this moment was a pivotal one in Microsoft’s history. Before there was Office, Windows 95, Xbox, or even AI, there was Altair BASIC—a product that he is still incredibly proud of to this day.
Download Altair BASIC’s Source Code
To mark the 50th anniversary of Microsoft, Bill Gates has decided to share the very source code that started it all. If you’re curious to explore this piece of computing history, you can download the full Altair BASIC source code from his Gates Notes blog.
The code is not just a historical artifact; it’s a look at the origins of modern computing, and it all began with the vision and determination of Bill Gates and Paul Allen.
