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 the 3.2 did that minor release receive its own version number (3.2.1). The best-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.