Apple II Disk OS Source Code at Computer History Museum

The Computer History Museum with the collaboration of the Digibarn Computer Museum and with permission from Apple Inc. posted the original 1978 source code for the Apple II DOS ‘Disk OS.’

The Apple II, Apple’s first mass-market computer, was hampered when first shipped in 1977 by having only a cassette tape drive for program and storage. Steve Wozniak soon created a hardware design for a floppy disk controller, but it needed software to organize the disk.

In a tour-de-force, Paul Laughton, a contractor for Shepardson Microsystems, wrote the Disk OS for the Apple II in only seven weeks, and Apple delivered it to customers in June of 1978.

The source code being released by the museum are scans of two listings and additional material that Paul had kept in his home office for 35 years.

“There was an amazing ‘can-do’ attitude among the engineers working on the early PCs in the 1970s and 1980s,” said Len Shustek, museum chairman. “Projects which would have taken years inside large companies were done in weeks or months. It is inspiring to see what they were able to do, with primitive tools, on computers that were tiny relative to today’s.“

“We are grateful that engineers like Paul are pack-rats, and preserve history that might otherwise be lost,” said John Hollar, museum’s president and CEO. “And we thank Bruce Damer of the Digibarn Computer Museum for collaborating with us to rescue these important artifacts. The preservation and release of this code is part of our ongoing commitment to software history, and we’re delighted to bring it to the world.“