Disk Operating System

86-DOS

a sample of a simulated session of 86-DOS

The predecessor of MS-DOS, 86-DOS, was developed by Seattle Computer Products for their machine based on intel 8086 processors.

In 1979, after having built the first 8086 microprocessor card, Seattle Computer needed a new operating system operating system. Digital Research was developing the new CP/M 86, which was supposed to be finished soon, but because of the limited amount of 8086 processors Seattle Computer had they were unable to send them one of those processors to help with the production of the new operating system. Since Microsoft was already developing software for the 8086, Seattle Computer helped them with their research, so that they could use Microsoft's software while waiting for the CP/M 86. At the end of 1979 the 8086 cards were shipped with a single software, Microsoft's Stand-Alone Disk BASIC, which had a built-in operating system. The months passed, though, and there was still no trace of the CP/M-86: for this reason, Seattle Computer decided to build themselves the operating system they needed, their own DOS.

The first version, called Quick and Dirty Operating System because of the small amount of time they had to write it, was delivered in August 1980. A new version of the 86-DOS came out before the end of 1980, and not much time later this DOS was bought by Microsoft, which then renamed it MS-DOS.

MS-DOS

a command line of MS-DOS

Microsoft licensed its new MS-DOS to other companies to use it for their own products. While at first they were free to change the name of the DOS, Microsoft soon decided to force those companies to keep the original name, DM-DOS. The only exception was IBM, which kept on developing its own version, PC DOS, to use for its IBM PC. In the meantime CP/M-86 came out, but because of the difference in price (the CP/M-86 costed almost 200 dollars more than its competitors) MS-DOS and PC DOS became soon the leaders of the market.

in version 2.0, which came out in March 1983, was added the support of hard disks and hierarchical subdirectories. This and other features permitted this version to be two times the size of the initial release.

Microsoft kept updating its operative system regularly until the 90s, when it started losing importance, being outdated by the new operative systems that came out in those years.

Apple DOS

an example of Applesoft BASIC

The Apple DOS was created to be used on the Apple II. In fact, when the Apple II came out, in 1977, it didn't have any operating system. Stephen Wozniak was trying to implement floppy disks on the machine to substitute the old cassette storage system, he and his friend Randy Wigginton wrote their first disk operating system, even though it wasn't really a complete operative system. They kept on updating it, though, adding new features little by little, until with the release 3.1 the Apple DOS was finally made available to the public in 1978.

The first version had some problems and bugs, and because of this a new version was soon released, which didn't have an updated version number. In 1979 version 3.2 was released, which implemented a new software, Applesoft II floating point BASIC, to substitute the old Integer BASIC program. This version also had doubled the number of different file types, which changed from four to eight.

Apple DOS 3.3 came out in 1980. This version was a general upgrade compared to version 3.2, improving the general performance in almost every field. 3.3 was however not backwards compatible, at least until Apple released a utility to which permitted to move old 3.2 files to the newer version. After this release Apple DOS lost importance, mainly because Apple was already working on its new product, the Apple III, which used a different operating system, which lead to the decline of the Apple DOS.