Enlarge / The Apple Lisa 1, released in 1983. (credit: Apple, Inc.)

As part of the Apple Lisa's 40th birthday celebrations, the Computer History Museum has released the source code for Lisa OS version 3.1 under an Apple Academic License Agreement. With Apple's blessing, the Pascal source code is available for download from the CHM website after filling out a form.

Lisa Office System 3.1 dates back to April 1984, during the early Mac era, and it was the equivalent of operating systems like macOS and Windows today.

The entire source package is about 26MB and consists of over 1,300 commented source files, divided nicely into subfolders that denote code for the main Lisa OS, various included apps, and the Lisa Toolkit development system.

Enlarge / Steve Jobs posing with the Lisa in 1983. (credit: Ted Thai)

Forty years ago today, a new type of personal computer was announced that would change the world forever. Two years later, it was almost completely forgotten.

The Apple Lisa started in 1978 as a new project for Steve Wozniak. The idea was to make an advanced computer using a bit-slice processor, an early attempt at scalable computing. Woz got distracted by other things, and the project didn’t begin in earnest until early 1979. That’s when Apple management brought in a project leader and started hiring people to work on it.

Lisa was named after Steve Jobs’ daughter, even though Jobs denied the connection and his parentage. But the more interesting thing about the Lisa computer was how it evolved into something unique: It was the first personal computer with a graphical user interface (GUI).