With permission from Apple, The Computer History Museum and the Digibarn Computer Museum announced today it is publishing the original DOS source code for Apple’s 1978 Apple II. The Apple II was the first fully assembled computer with a monitor that Apple sold following the Apple I and originally retailed for $1298 for the base model with just 4K of memory.

A blog post from The History Computer Museum explains that Apple contracted Paul Laughton of Shepardson Microsystems to write the Disk Operating System for the Apple II in just seven weeks. In April of 78, Steve Jobs and Shepardson signed a contract (pictured below) that would see Apple pay $13,000 for a file manager, a BASIC interface, and utilities. The source code being released today is scans of original documents that Laughton kept over the last 30+ years:

Steve Wozniak soon created a brilliant hardware design for a floppy disk controller, but it needed software to organize the disk… On April 10, 1978 Bob Shepardson and Steve Jobs signed a $13,000 one-page contract for a file manager, a BASIC interface, and utilities. It specified that “Delivery will be May 15″, which was incredibly aggressive. But, amazingly, “Apple II DOS version 3.1″ was released in June 1978. In an incredible tour-de-force, Paul Laughton, a contractor for Shepardson Microsystems, wrote the Disk Operating System for the Apple II in only seven weeks, and Apple delivered it to eager customers in June of 1978.

The museums are also releasing source code for other historic software including Apple’s Macpaint and Quickdraw and Adobe Photoshop. You can view the source code for the Apple II on The Computer History Museum’s website here, which also has an in-depth history of how Paul hooked up with Apple and worked with Woz and others to create the DOS.

You’ll also find some other documents that Laughton has kept over the years including meeting notes and the original contracts between Steve Jobs and Shepardson Microsystems to write the Apple II DOS:

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