DOS served as the basis for the first widely used operating system. Disk operating systems made personal computers workable using data reading and data storage on floppy disks. Computers could be con­trolled with a simple text-based command line, making DOS not only user friendly but also efficient and highly func­tion­al.

The de­vel­op­ment of DOS (disk operating system)

After Bill Gates found out that IBM was looking for an al­tern­at­ive operating system to the one it had ori­gin­ally planned, he bought the rights to QDOS (Quick and Dirty Operating System) from a small software company. IBM acquired the license from Microsoft and in­teg­rated it into the IBM PC as PC-DOS 1.0.

PC-DOS took in­spir­a­tion from CP/M (the operating system IBM had ori­gin­ally planned) and Unix but was found to be lacking in its execution. It turned out to be a rather poorly pro­grammed operating system, leading Microsoft to com­pletely reprogram it. PC-DOS 2.0 then came to market as the first reas­on­ably func­tion­ing operating system.

Since IBM did not have an exclusive license for the operating system, Microsoft could also sell it to other companies. Under the name MS-DOS, it became one of the most popular operating systems of its time. In 1982, over 50 companies had licensing agree­ments for Microsoft’s disk operating system.

As time went on, DOS users asked more and more of their graphical user interface (GUI). Microsoft fulfilled this wish in 1985 with Windows 1.0, which imitated the GUI developed by Xerox back in the 1970s. Apple also launched with a GUI around this time. Users thus no longer had to type commands to open programs - they could simply click on an icon with their mouse.

DOS: Well-known examples

CP/M and PC-DOS/MS-DOS aren’t the only well-known disk operating systems. Other widely used DOS include:

  • Commodore DOS: Commodore DOS was developed in 1977 and is located on the disk rather than in the computer, setting it apart from most other disk operating systems. This actually makes it a firmware rather than an operating system.
  • Apple DOS: Back in the day, Apple computers were only com­pat­ible with audio cassettes. In 1978, Apple expanded its func­tion­al­ity and in­teg­rated the Apple DOS into the Apple II computer. After the in­tro­duc­tion of 16-bit ar­chi­tec­ture, Apple DOS gave way to GS/OS and even­tu­ally developed into the macOS that’s used today.
  • AmigaDOS: AmigaDOS made use of in­nov­at­ive ap­proaches such as mi­croker­nel ar­chi­tec­ture and addable device drivers, which are still used in modern operating systems. The operating system has its origins in Cambridge Uni­ver­sity’s multiuser system TRIPOS.
  • Atari DOS: What made the Atari DOS special was the in­teg­rated memory-resident kernel in version 2.0. With version 4.0, Atari DOS became freely ac­cess­ible as part of the public domain, meaning that there are countless de­riv­at­ives of Atari pro­grammed by third-parties.

How does DOS work?

DOS handles in­form­a­tion and commands using batch files and can thus process data in­tern­ally. When a user starts their computer, the system processes it in a batch file, which is contained in the self-executing file autoexec.bat. The file checks all system com­pon­ents and monitors the startup process. Once autoexec.bat has finished pro­cessing the batch file, a blinking cursor appears, and the user can enter commands using their keyboard.

Basic commands in DOS

After the computer has suc­cess­fully booted DOS, the command line in­ter­pret­er COMMAND.COM will start auto­mat­ic­ally. Users can then enter commands using the keyboard. Many important commands are already in­teg­rated into DOS. The in­ter­pret­er will search for unknown commands in files with endings like ‘.EXE’, ‘.COM’ or ‘.BAT’.

Here are some of the most basic disk operating system commands:

Command Type Ex­plan­a­tion
CD <Directory-name> Internal Changes to the directory specified. If you enter a backslash ‘\’ before the directory name, the DOS will interpret the command with respect to the current directory. Back­slashes are also used to separate directory names.
DEL <File-name> Internal Deletes one or more files.
DELTREE <Directory-name> External Deletes the entire directory, including all contents and sub-dir­ect­or­ies.
MD <Directory-name> Internal Creates a new directory with the name indicated.
Tip

You can find an extensive list of DOS commands in our article ‘DOS Commands: A overview of the most important commands’.

DOS today

Windows 95 heralded the end of the DOS era. After that, the disk operating system lost in sig­ni­fic­ance with each new version of Windows. Modern Windows systems do still support MS-DOS, but users only turn to it in special cases. If you want to open older DOS programs, you should use an emulator, which will recreate the old ar­chi­tec­ture.

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