Apple DOS

Apple DOS is a disk operating system, developed for the Apple II series from 1978 through early 1983 (when it was replaced by ProDOS), after the release of Microsoft Basic. Apple DOS has three major releases: 3.1, 3.2 and 3.3; each one of these three releases was followed by a second, minor "bug-fix" release, but only with version 3.2, that minor release received its own version number (3.2.1). The most well-known and most-used version is 3.3 in the 1980 and 1983 releases. Prior to the release of 3.1, users had to rely on audio cassette tapes for data storage and retrieval.

History
After the launch of the Apple II in April 1977, the computer had no disk drive or disk operating system (DOS). Although Steve Wozniak designed the Disk II controller late that year, and believed that he could have written a DOS, Steve Jobs decided to outsource the task. The company considered using CP/M, but Wozniak sought an operating system that was easy to use. In 1978 Apple signed a $13,000 contract with Shepardson Microsystems to write a DOS and deliver it within 35 days. Apple provided detailed specifications, and a former employee Randy Wigginton worked closely with Shepardson's Paul Laughton as the latter wrote the system with punched cards and a minicomputer.

There was not a version 1 or 2. These versions were serially enumerated revisions during development, which might as well have been called builds 1 through 28. Apple DOS 3.0, was never publicly released due to bugs. Apple published no official documentation until release 3.2.

After 1980, Apple DOS entered into a state of stagnation for the company to focus on SOS, the Apple III system. There were two more versions of Apple DOS (both 3.3) fixing bugs and better support for Apple IIe.