**In a nutshell:** Microsoft, founded by Bill Gates and Paul Allen in April 1975, is celebrating its 50th anniversary this month. To mark the occasion, Gates has released the source code he and Allen wrote for the Altair 8800 – dubbed Altair BASIC – which became the company's first product.
Reminiscing about Microsoft's early days, Gates said Altair BASIC was the company's "original source code," predating iconic products like Windows and Office. While he went on to write plenty of code for Microsoft in the years that followed, Gates holds Altair BASIC especially close to his heart, calling it the "coolest code I've ever written."
He also shared a [humorous anecdote](https://www.gatesnotes.com/microsoft-original-source-code) about how the code came to be. In the early 1970s, he and Allen reached out to the creators of the Altair 8800, claiming they had already developed a version of the BASIC programming language for the computer's processor. There was just one problem: the program didn't actually exist yet. Determined to deliver on their promise, they "coded day and night for two months to create the software we said already existed."
When the software was finally demonstrated to the president of MITS (the company behind the Altair), he was suitably impressed. MITS agreed to license the program, making Altair BASIC the first-ever product from Microsoft.
Describing Microsoft's 50th anniversary as "bittersweet," Gates said it still feels like yesterday when he and Allen wrote the Altair BASIC code on a PDP-10 mainframe in Harvard's computer lab. He added that even after all these years, he still gets a kick out of seeing the original code, which is now available for [download](https://images.gatesnotes.com/12514eb8-7b51-008e-41a9-512542cf683b/34d561c8-cf5c-4e69-af47-3782ea11482e/Original-Microsoft-Source-Code.pdf) on his official blog.
Gates also revealed that Altair BASIC was inspired by the January 1975 issue of Popular Electronics magazine, which featured a photograph of the Altair 8800 microcomputer. Seeing it for the first time sparked his fascination and motivated him to focus on coding as a career. In an accompanying video, Gates described the program as a "revolution" and credited it with ushering in the era of personal computing.
Reflecting on the past 50 years, Gates said he and Allen founded Microsoft with the dream of putting a computer on every desk, everywhere. He thanked former CEO Steve Ballmer, current CEO Satya Nadella, and Microsoft's employees and executives for helping that dream become a reality.