The Computer History Museum has published the source code of Apple II DOS for the first time - for non-commercial use, of course. This is the code that arguably helped propel Apple into a serious contender during the early days of personal computing.

The Apple II was a legit computer when it debut in the late ‘70s. The $1,298 machine (with 4K of memory) had color, graphics, sound, expansion slots, game paddles and a built-in BASIC programming language. It was ready to work with any display but the one thing it didn’t have was a disk drive.

Instead, users had to rely on cassette tape recorders for storage which was slow and unreliable at the time. These were also expensive and required hardware controllers and complex software to use but Apple ultimately found a solution.

Steve Wozniak created a floppy disk controller that used just eight integrated circuits. The difference between his controller and others was the fact that his system worked in programmed logic versus controllers that relied on hardware.

Higher-level software necessary to organize and access programs and data on the disk was still needed. Apple didn’t have the staff or the time to create it so they reached out to Shepardson Microsystems contract programmer Paul Laughton to build a file manager, a BASIC interface and utilities. He was hired to do the job on April 10, 1978 by Steve Jobs and Bob Shepardson for $13,000 through the use of a one-page contract.