Disk Operating System

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As a Disk Operating System ( english [ dɪsk ɒpəɹeɪtɪŋ sɪstəm ]; short DOS ) is an operating system (for a computer called), which focuses the management of (magnetic) stored information in the form of files on rotating (disk) storage media such as floppy disks and hard drives is.

Today this term is used almost exclusively as a synonym for MS-DOS , which was the most widespread operating system with this focus until the late 1990s.



A disk operating system consists at least of

  • a core anchored in the operating system for the consistency of the stored structures in the respective file system ( API for programs),
  • a user interface for operation (e.g. via COMMAND.COM ),
  • numerous commands for managing the file system, especially z. B. for formatting , copying, sorting files, displaying the contents of the storage medium ( dir ),
  • a simple main memory management to load programs to be executed into free memory areas and to execute them there.


Operating system from the DOS types usually very rudimentary access methods offered to the memory, often without an organization in the "Files" - data and programs were written directly to assigned areas, the operator / operator manage had sometimes even (on paper) where what was saved.

The DOS operating systems established terms and understanding of what a “file” is or a “file system”, and offered comparatively convenient commands to handle files (and directories) (create, delete, copy, rename, group into directories, etc.) .

Today's operating systems also have all of these capabilities and offer even more convenient methods for file handling, e.g. B. (graphical) file manager . However, they now focus on other properties and therefore i. A. the abbreviation "DOS" no longer in the name.



The roots of DOS systems lie in the mainframe operating systems . In the 1960s, IBM delivered the DOS / 360 as the operating system for mainframe systems of the System / 360 generation as the successor and further development of the TOS (" Tape Operating System "). Under DOS it was possible for the first time to process several program sequences ( batch jobs ) in parallel without IPL , and thus to go beyond the purely sequential write and read processes of the tape drive and to carry out distributed, so-called "random" accesses, as is required for Magnetic disk storage media is common.

Another important step was the OS / 360 systems since 1966, the time- sharing- enabled CP / CMS systems since 1967, and Unix ( AT&T ) since 1969, with which the storage management is integrated into a more complex operating system.

Numerous other disk operating systems followed in the course of the 1970s.


The AmigaDOS was the DOS of the Commodore Amiga and core component of AmigaOS after 1985. This DOS was based on the multiuser system TRIPOS from Cambridge University and implemented revolutionary approaches at the time, such as microkernel architecture and reloadable device drivers, as is common today in all modern higher operating systems is.

Apple DOS

Apple DOS was launched by Apple in July 1978 for the Apple II generation. It appeared in version 3.1, the predecessors were internal development versions. Before that, Apple computers could only save to audio cassettes. The most widespread Apple DOS version is DOS 3.3 from August 1980, in 1983 it was replaced by the more powerful Apple ProDOS , which in addition to the previous 13 cm (5.25 inch) floppy disks also includes the new 9 cm (3 , 5-inch) floppy disks as well as hard disks supported. With the advent of the 16-bit architecture , the Apple DOS systems became part of the graphic operating systems GS / OS and, from 1984, Mac OS .

Atari DOS

The Atari DOS from Atari came on the market in 1979. Version 2.0 already had a real memory resident kernel (DUP.SYS). It became public domain after version 4.0 and has produced a number of derivatives from third parties.

Atari DOS must not be confused with Ataris TOS or GEMDOS - the latter a DOS for 68000 processors originally conceived by Digital Research as a substructure for GEM, which is remotely based on MS-DOS, without being binary compatible with it.

Commodore DOS

Commodore DOS / CBM DOS is the system developed by Commodore Business Machines for the Commodore PET from 1977. Unlike its competing products, it is not in the computer, but in the floppy disk drive itself, and is therefore not a computer operating system, but that of the storage hardware itself, i.e. firmware . This DOS was first delivered with the Commodore 2040/3040 floppy drives. The last generation, the 1581 model in 3.5 ″ format, were sufficiently PC-compatible, but the concept of the floppy disk controller firmware has disappeared.

( Commodore DOS must not be confused with Commodore MS-DOS , an MS-DOS OEM version that was delivered with later IBM PC-compatible Commodore PCs and is covered in the article PC-compatible DOS .)

CP / M

CP / M from Digital Research was a very popular in the late 1970s and early 1980s operating system for 8-bit CPUs. It is the only noteworthy DOS system for microcomputers before 1980. It was roughly based on the TOPS-10 (Timesharing / Total OS) for mainframes, but it is more simply structured because the demands on these early computers were much lower than on mainframes : In particular, the permanent storage work only took place on floppy disks , which was developed by IBM for the System 360 in 1969 - hard disks did not establish themselves on the home customer market until the mid-1980s. It is the first platform-independent operating system for this market and introduced the technology of the hardware abstraction layer , which separates the file system work of the BDOS (Basic Disk Operating System) from the hardware-related BIOS ( Basic Input Output System ) for the device drivers .

PC compatible DOS

Due to the widespread use of PCs, which can be traced back to the IBM PC and computers that are more or less compatible with them, the family of operating systems compatible with MS-DOS has emerged (in the PC context often simply referred to as "DOS-compatible") ), the main representatives of which are MS-DOS from Microsoft and PC DOS from IBM .

MS-DOS and PC DOS was originally called QDOS / 86-DOS 1980 by Tim Paterson of Seattle Computer Products as CP / M-80 - clone of Intel 8086 processors / x86 Computers ( IBM PC-compatible computers ) developed because the presentation of CP / M-86 for 8086 processors by Digital Research was a long time coming. The easy adaptability of the source texts to new systems was in the foreground during the development of CP / M, therefore 86-DOS was based very closely on the model, but without offering binary compatibility. 86-DOS was later bought by Microsoft, licensed to IBM and jointly developed by both companies as MS-DOS and PC DOS. The CP / M-86, which is also available in the meantime, was offered at a higher price and, despite some of its more extensive capabilities, fell increasingly behind MS-DOS / PC DOS.

Over the decades various operating systems compatible with MS-DOS / PC DOS have been developed, including: a. also from Digital Research itself (Concurrent DOS, Multiuser DOS, DOS Plus, DR-DOS , DR PalmDOS), from which further systems (such as FlexOS, Datapac System Manager, IMS REAL / 32, Novell DOS or Caldera OpenDOS) were created. Other alternative DOS systems are, for example, Datalight ROM-DOS, General Software Embedded DOS, PTS-DOS , RxDOS, FreeDOS .

MS-DOS / PC DOS and alternative compatible DOS systems are referred to as PC-compatible DOS .

Other DOS operating systems

  • In the 1970s there were on the computers HP 1000 from Hewlett-Packard , a single-user operating system (Engl. Single-user OS ) called DOS
  • DOS-11: simple operating system for PDP-11 computers from DEC
  • PalmDOS : used among other things on screen typewriters from Olivetti (not to be confused with the DR PalmDOS developed under the code name Merlin in the early 1990s, a special DR DOS variant for mobile systems such as handhelds, which is dealt with in the article PC-compatible DOS )
  • MSX-DOS : from Microsoft for MSX computers

Web links

Individual evidence

  1. see DOS / 360 and successors , engl. Wikipedia
  2. see TOS / 360 , engl. Wikipedia
  3. see History of CP / CMS , engl. Wikipedia
  4. see Timeline of operating systems , engl. Wikipedia
  5. see AmigaDOS , engl. Wikipedia
  6. see Commodore 4040 , engl. Wikipedia
  7. see Commodore 1581 , engl. Wikipedia