Disk operating system
Encyclopedia
Disk Operating System (specifically) and disk operating system (generically), most often abbreviated as DOS, refers to an operating system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...

 software used in most computers that provides the abstraction and management of secondary storage devices and the information on them (e.g., file system
File system
A file system is a means to organize data expected to be retained after a program terminates by providing procedures to store, retrieve and update data, as well as manage the available space on the device which contain it. A file system organizes data in an efficient manner and is tuned to the...

s for organizing files of all sorts). Such software is referred to as a disk operating system when the storage devices it manages are made of rotating platters, such as floppy disk
Floppy disk
A floppy disk is a disk storage medium composed of a disk of thin and flexible magnetic storage medium, sealed in a rectangular plastic carrier lined with fabric that removes dust particles...

s or hard disk
Hard disk
A hard disk drive is a non-volatile, random access digital magnetic data storage device. It features rotating rigid platters on a motor-driven spindle within a protective enclosure. Data is magnetically read from and written to the platter by read/write heads that float on a film of air above the...

s.

In the early days of microcomputer
Microcomputer
A microcomputer is a computer with a microprocessor as its central processing unit. They are physically small compared to mainframe and minicomputers...

s, computer memory
Computer memory
In computing, memory refers to the physical devices used to store programs or data on a temporary or permanent basis for use in a computer or other digital electronic device. The term primary memory is used for the information in physical systems which are fast In computing, memory refers to the...

 space was often limited, so the disk operating system was an extension of the operating system. This component was only loaded if needed. Otherwise, disk access would be limited to low-level operations such as reading and writing disks at the sector
Disk sector
In computer disk storage, a sector is a subdivision of a track on a magnetic disk or optical disc. Each sector stores a fixed amount of user data. Traditional formatting of these storage media provides space for 512 bytes or 2048 bytes of user-accessible data per sector...

-level.

In some cases, the disk operating system component (or even the operating system) was known as DOS.

Sometimes, a disk operating system can refer to the entire operating system if it is loaded off a disk and supports the abstraction and management of disk devices. Examples include DOS/360
DOS/360
Disk Operating System/360, also DOS/360, or simply DOS, was an operating system for IBM mainframes. It was announced by IBM on the last day of 1964, and it was first delivered in June 1966....

 and FreeDOS
FreeDOS
FreeDOS is an operating system for IBM PC compatible computers. FreeDOS is made up of many different, separate programs that act as "packages" to the overall FreeDOS Project...

. On the PC compatible platform, an entire family of operating systems was called DOS.

History

In the early days of computers, there were no disk drives; delay line
Digital delay line
A digital delay line is a discrete element in digital filter theory, which allows a signal to be delayed by a number of samples. If the delay is an integer multiple of samples digital delay lines are often implemented as circular buffers...

s, punched card
Punched card
A punched card, punch card, IBM card, or Hollerith card is a piece of stiff paper that contains digital information represented by the presence or absence of holes in predefined positions...

s, paper tape, magnetic tape
Magnetic tape
Magnetic tape is a medium for magnetic recording, made of a thin magnetizable coating on a long, narrow strip of plastic. It was developed in Germany, based on magnetic wire recording. Devices that record and play back audio and video using magnetic tape are tape recorders and video tape recorders...

, magnetic drums, were used instead. And in the early days of microcomputers, paper tape or audio cassette tape (see Kansas City standard
Kansas City standard
The Kansas City Standard , or Byte standard, is a digital data format for audio cassette drives. Byte magazine sponsored a symposium in November 1975 in Kansas City, Missouri to develop a standard for storage of digital computer data on inexpensive consumer quality cassettes, at a time when...

) or nothing were used instead. In the latter case, program and data entry was done at front panel
Front panel
A front panel was used on early electronic computers to display and allow the alteration of the state of the machine's internal registers and memory. The front panel usually consisted of arrays of indicator lamps, toggle switches, and push buttons mounted on a sheet metal face plate...

 switches directly into memory or through a computer terminal
Computer terminal
A computer terminal is an electronic or electromechanical hardware device that is used for entering data into, and displaying data from, a computer or a computing system...

 / keyboard, sometimes controlled by a read-only memory
Read-only memory
Read-only memory is a class of storage medium used in computers and other electronic devices. Data stored in ROM cannot be modified, or can be modified only slowly or with difficulty, so it is mainly used to distribute firmware .In its strictest sense, ROM refers only...

 (ROM) BASIC
BASIC
BASIC is a family of general-purpose, high-level programming languages whose design philosophy emphasizes ease of use - the name is an acronym from Beginner's All-purpose Symbolic Instruction Code....

 interpreter; when power was turned off after running the program, the information so entered vanished.

Both hard disk
Hard disk
A hard disk drive is a non-volatile, random access digital magnetic data storage device. It features rotating rigid platters on a motor-driven spindle within a protective enclosure. Data is magnetically read from and written to the platter by read/write heads that float on a film of air above the...

s and floppy disk
Floppy disk
A floppy disk is a disk storage medium composed of a disk of thin and flexible magnetic storage medium, sealed in a rectangular plastic carrier lined with fabric that removes dust particles...

 drives require software to manage rapid access to block storage of sequential and other data. When microcomputers rarely had expensive disk drives of any kind, the need to have software to manage such devices (the disks) carried much status. To have one or the other was a mark of distinction and prestige, and so was having the Disk sort of an Operating System. As prices for both disk hardware and operating system software decreased, there were many such microcomputer systems.

Mature versions of the Commodore
Commodore 64
The Commodore 64 is an 8-bit home computer introduced by Commodore International in January 1982.Volume production started in the spring of 1982, with machines being released on to the market in August at a price of US$595...

, SWTPC
SWTPC
The U.S. company SWTPC started in 1964 as DEMCO . It was incorporated in 1967 as Southwest Technical Products Corporation of San Antonio, Texas...

, Atari
Atari 8-bit family
The Atari 8-bit family is a series of 8-bit home computers manufactured from 1979 to 1992. All are based on the MOS Technology 6502 CPU and were the first home computers designed with custom coprocessor chips...

 and Apple
Apple Computer
Apple Inc. is an American multinational corporation that designs and markets consumer electronics, computer software, and personal computers. The company's best-known hardware products include the Macintosh line of computers, the iPod, the iPhone and the iPad...

 home computer
Home computer
Home computers were a class of microcomputers entering the market in 1977, and becoming increasingly common during the 1980s. They were marketed to consumers as affordable and accessible computers that, for the first time, were intended for the use of a single nontechnical user...

 systems all featured a disk operating system (actually called 'DOS' in the case of the Commodore 64 (CBM DOS), Atari 800 (Atari DOS
Atari DOS
Atari DOS is the disk operating system used with the Atari 8-bit family of computers. Operating system extensions loaded into memory were required in order for an Atari computer to access a disk drive. These extensions to the operating system added the disk handler and other file management...

), and Apple II machines (Apple DOS
Apple DOS
Apple DOS refers to operating systems for the Apple II series of microcomputers from late 1978 through early 1983. Apple DOS had three major releases: DOS 3.1, DOS 3.2, and DOS 3.3; each one of these three releases was followed by a second, minor "bug-fix" release, but only in the case of Apple DOS...

)), as did (at the other end of the hardware spectrum, and much earlier) IBM
IBM
International Business Machines Corporation or IBM is an American multinational technology and consulting corporation headquartered in Armonk, New York, United States. IBM manufactures and sells computer hardware and software, and it offers infrastructure, hosting and consulting services in areas...

's System/360
System/360
The IBM System/360 was a mainframe computer system family first announced by IBM on April 7, 1964, and sold between 1964 and 1978. It was the first family of computers designed to cover the complete range of applications, from small to large, both commercial and scientific...

, 370
System/370
The IBM System/370 was a model range of IBM mainframes announced on June 30, 1970 as the successors to the System/360 family. The series maintained backward compatibility with the S/360, allowing an easy migration path for customers; this, plus improved performance, were the dominant themes of the...

 and (later) 390 series of mainframe
IBM mainframe
IBM mainframes are large computer systems produced by IBM from 1952 to the present. During the 1960s and 1970s, the term mainframe computer was almost synonymous with IBM products due to their marketshare...

s (e.g., DOS/360
DOS/360
Disk Operating System/360, also DOS/360, or simply DOS, was an operating system for IBM mainframes. It was announced by IBM on the last day of 1964, and it was first delivered in June 1966....

: Disk Operating System / 360 and DOS/VSE: Disk Operating System / Virtual Storage Extended). Most home computer DOS'es were stored on a floppy disk always to be booted at start-up, with the notable exception of Commodore, whose DOS resided on ROM chips in the disk drive
Commodore 1541
The Commodore 1541 , made by Commodore International, was the best-known floppy disk drive for the Commodore 64 home computer. The 1541 was a single-sided 170 kilobyte drive for 5¼" disks...

s themselves (the computer itself had no DOS, just a form of a BIOS
BIOS
In IBM PC compatible computers, the basic input/output system , also known as the System BIOS or ROM BIOS , is a de facto standard defining a firmware interface....

 for communicating with peripherals). The Lt. Kernal
Lt. Kernal
Lt. Kernal was the name given to a SCSI hard drive subsystem developed for the Commodore 64 and Commodore 128 home computers. The original design of both the technically complicated hardware interface and equally complex disk operating system came from Lloyd Sponenburgh and Roy Southwick of Fiscal...

 hard disk
Hard disk
A hard disk drive is a non-volatile, random access digital magnetic data storage device. It features rotating rigid platters on a motor-driven spindle within a protective enclosure. Data is magnetically read from and written to the platter by read/write heads that float on a film of air above the...

 subsystem for the Commodore 64
Commodore 64
The Commodore 64 is an 8-bit home computer introduced by Commodore International in January 1982.Volume production started in the spring of 1982, with machines being released on to the market in August at a price of US$595...

 and Commodore 128
Commodore 128
The Commodore 128 home/personal computer was the last 8-bit machine commercially released by Commodore Business Machines...

 models stored its DOS on the disk, as is the case with modern systems, and loaded the DOS into RAM
Ram
-Animals:*Ram, an uncastrated male sheep*Ram cichlid, a species of freshwater fish endemic to Colombia and Venezuela-Military:*Battering ram*Ramming, a military tactic in which one vehicle runs into another...

 at boot time.

In large machines there were other disk operating systems, such as IBM's VM
VM (operating system)
VM refers to a family of IBM virtual machine operating systems used on IBM mainframes System/370, System/390, zSeries, System z and compatible systems, including the Hercules emulator for personal computers. The first version, released in 1972, was VM/370, or officially Virtual Machine Facility/370...

, DEC's RSTS
RSTS/E
RSTS is a multi-user time-sharing operating system, developed by Digital Equipment Corporation , for the PDP-11 series of 16-bit minicomputers. The first version of RSTS was implemented in 1970 by DEC software engineers that developed the TSS-8 time-sharing operating system for the PDP-8...

 / RT-11
RT-11
RT-11 was a small, single-user real-time operating system for the Digital Equipment Corporation PDP-11 family of 16-bit computers...

 / VMS
OpenVMS
OpenVMS , previously known as VAX-11/VMS, VAX/VMS or VMS, is a computer server operating system that runs on VAX, Alpha and Itanium-based families of computers. Contrary to what its name suggests, OpenVMS is not open source software; however, the source listings are available for purchase...

 / TOPS-10
TOPS-10
The TOPS-10 System was a computer operating system from Digital Equipment Corporation for the PDP-10 mainframe computer launched in 1967...

 / TWENEX, MIT's ITS
Incompatible Timesharing System
ITS, the Incompatible Timesharing System , was an early, revolutionary, and influential time-sharing operating system from MIT; it was developed principally by the Artificial Intelligence Laboratory at MIT, with some help from Project MAC.In addition to being technically influential ITS, the...

 / CTSS, Control Data's assorted NOS
Network operating system
A networking operating system , also referred to as the Dialoguer, is the software that runs on a server and enables the server to manage data, users, groups, security, applications, and other networking functions...

 variants, Harris's Vulcan, Bell Labs' Unix
Unix
Unix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna...

, and so on. In microcomputer
Microcomputer
A microcomputer is a computer with a microprocessor as its central processing unit. They are physically small compared to mainframe and minicomputers...

s, SWTPC's 6800 and 6809 machines used TSC
Technical Systems Consultants
Technical Systems Consultants was a US software company.Headquartered first in West Lafayette, Indiana and later moved to Chapel Hill, North Carolina, it was the foremost supplier of software for SWTPC compatible hardware, as well as many other early makes of personal computers...

's FLEX
FLEX (operating system)
The FLEX single-tasking operating system was developed by Technical Systems Consultants of West Lafayette, Indiana, for the Motorola 6800 in 1976. The original version was for 8" floppy disks and the version for 5.25" floppies was called mini-Flex. It was also later ported to the Motorola 6809;...

 disk operating system, Radio Shack
Radio shack
Radio shack is a slang term for a room or structure for housing radio equipment.-History:In the early days of radio, equipment was experimental and home-built. The first radio transmitters used a noisy spark to generate radio waves and were often housed in a garage or shed. When radio was first...

's TRS-80
TRS-80
TRS-80 was Tandy Corporation's desktop microcomputer model line, sold through Tandy's Radio Shack stores in the late 1970s and early 1980s. The first units, ordered unseen, were delivered in November 1977, and rolled out to the stores the third week of December. The line won popularity with...

 machines used TRS-DOS
TRS-DOS
TRS-DOS was the operating system for the Tandy TRS-80 line of 8-bit Zilog Z80 microcomputers that were sold through Radio Shack through the late 1970s and early 1980s. Tandy's manuals recommended that it be pronounced triss-doss...

, their Color Computer
TRS-80 Color Computer
The Radio Shack TRS-80 Color Computer was a home computer launched in 1980. It was one of the earliest of the first generation of computers marketed for home use in English-speaking markets...

 used OS-9
OS-9
OS-9 is a family of real-time, process-based, multitasking, multi-user, Unix-like operating systems, developed in the 1980s, originally by Microware Systems Corporation for the Motorola 6809 microprocessor. It is currently owned by RadiSys Corporation....

, and most of the Intel 8080 based machines from IMSAI, MITS
Micro Instrumentation and Telemetry Systems
Micro Instrumentation and Telemetry Systems was an American electronics company founded in Albuquerque, New Mexico that began manufacturing electronic calculators in 1971 and personal computers in 1975. Ed Roberts and Forrest Mims founded MITS in December 1969 to produce miniaturized telemetry...

 (makers of the legendary Altair 8800
Altair 8800
The MITS Altair 8800 was a microcomputer design from 1975 based on the Intel 8080 CPU and sold by mail order through advertisements in Popular Electronics, Radio-Electronics and other hobbyist magazines. The designers hoped to sell only a few hundred build-it-yourself kits to hobbyists, and were...

), Cromemco
Cromemco
Cromemco was a Mountain View, California microcomputer company known for its high-end Z80-based S-100 bus computers in the early days of the home computer revolution. The Cromemco Dazzler was the first color graphics card available for personal computers....

, North Star, etc., used the CP/M-80 disk operating system. See list of operating systems.

Usually, a disk operating system was loaded from a disk. Only a very few comparable DOSes were stored elsewhere than floppy disks; among these exceptions were the British BBC Micro
BBC Micro
The BBC Microcomputer System, or BBC Micro, was a series of microcomputers and associated peripherals designed and built by Acorn Computers for the BBC Computer Literacy Project, operated by the British Broadcasting Corporation...

's optional Disc Filing System
Disc Filing System
The Disc Filing System is a computer file system developed by Acorn Computers Ltd, and introduced in 1982 for the Acorn BBC Microcomputer. It was shipped as a ROM to be inserted onto the BBC Micro's motherboard. It has an extremely limited design, and uses a flat directory structure...

, DFS, offered as a kit with a disk controller chip, a ROM chip, and a handful of logic chips, to be installed inside the computer; and Commodore
Commodore International
Commodore is the commonly used name for Commodore Business Machines , the U.S.-based home computer manufacturer and electronics manufacturer headquartered in West Chester, Pennsylvania, which also housed Commodore's corporate parent company, Commodore International Limited...

's CBM DOS
Commodore DOS
Commodore DOS, aka CBM DOS, was the disk operating system used with Commodore's 8-bit computers. Unlike most other DOS systems before or since—which are booted from disk into the main computer's own RAM at startup, and executed there—CBM DOS was executed internally in the drive: the DOS...

, located in a ROM chip in each disk drive.

Disk operating systems that were extensions to the OS

  • The DOS operating system was the primary operating system for the Apple Computer
    Apple Computer
    Apple Inc. is an American multinational corporation that designs and markets consumer electronics, computer software, and personal computers. The company's best-known hardware products include the Macintosh line of computers, the iPod, the iPhone and the iPad...

    's Apple II
    Apple II
    The Apple II is an 8-bit home computer, one of the first highly successful mass-produced microcomputer products, designed primarily by Steve Wozniak, manufactured by Apple Computer and introduced in 1977...

     family of computers, from 1979 with the introduction of the floppy disk drive, until 1983 with the introduction of ProDOS
    ProDOS
    ProDOS was the name of two similar operating systems for the Apple II series of personal computers. The original ProDOS, renamed ProDOS 8 in version 1.2, was the last official operating system usable by all Apple II series computers, and was distributed from 1983 to 1993...

    ; many people continued using it long after that date. Usually, it was called Apple DOS
    Apple DOS
    Apple DOS refers to operating systems for the Apple II series of microcomputers from late 1978 through early 1983. Apple DOS had three major releases: DOS 3.1, DOS 3.2, and DOS 3.3; each one of these three releases was followed by a second, minor "bug-fix" release, but only in the case of Apple DOS...

    to distinguish it from MS-DOS
    MS-DOS
    MS-DOS is an operating system for x86-based personal computers. It was the most commonly used member of the DOS family of operating systems, and was the main operating system for IBM PC compatible personal computers during the 1980s to the mid 1990s, until it was gradually superseded by operating...

    .
  • Commodore DOS
    Commodore DOS
    Commodore DOS, aka CBM DOS, was the disk operating system used with Commodore's 8-bit computers. Unlike most other DOS systems before or since—which are booted from disk into the main computer's own RAM at startup, and executed there—CBM DOS was executed internally in the drive: the DOS...

    , which was used by 8-bit Commodore
    Commodore International
    Commodore is the commonly used name for Commodore Business Machines , the U.S.-based home computer manufacturer and electronics manufacturer headquartered in West Chester, Pennsylvania, which also housed Commodore's corporate parent company, Commodore International Limited...

     computers. Unlike most other DOS systems, it was integrated into the disk drives, not loaded into the computer's own memory.
  • Atari DOS
    Atari DOS
    Atari DOS is the disk operating system used with the Atari 8-bit family of computers. Operating system extensions loaded into memory were required in order for an Atari computer to access a disk drive. These extensions to the operating system added the disk handler and other file management...

    , which was used by the Atari 8-bit family
    Atari 8-bit family
    The Atari 8-bit family is a series of 8-bit home computers manufactured from 1979 to 1992. All are based on the MOS Technology 6502 CPU and were the first home computers designed with custom coprocessor chips...

     of computers. The Atari OS only offered low-level disk-access, so an extra layer called DOS was booted off a floppy that offered higher level functions such as filesystems.
  • MSX-DOS
    MSX-DOS
    MSX-DOS is a Disk operating system developed by Microsoft for the 8-bit home computer standard MSX, and is a cross between MS-DOS rev 1.0 and CP/M.-MSX-DOS:...

    , for the MSX
    MSX
    MSX was the name of a standardized home computer architecture in the 1980s conceived by Kazuhiko Nishi, then Vice-president at Microsoft Japan and Director at ASCII Corporation...

     computer standard. Initial version, released in 1984, was nothing but MS-DOS 1.0 ported to Z80
    Zilog Z80
    The Zilog Z80 is an 8-bit microprocessor designed by Zilog and sold from July 1976 onwards. It was widely used both in desktop and embedded computer designs as well as for military purposes...

    ; but in 1988 it evolved to version 2, offering facilities such as subdirectories, memory management and environment strings. The MSX-DOS kernel resided in ROM (built-in on the disk controller) so basic file access capacity was available even without the command interpreter, by using BASIC
    BASIC
    BASIC is a family of general-purpose, high-level programming languages whose design philosophy emphasizes ease of use - the name is an acronym from Beginner's All-purpose Symbolic Instruction Code....

     extended commands.
  • Disc Filing System
    Disc Filing System
    The Disc Filing System is a computer file system developed by Acorn Computers Ltd, and introduced in 1982 for the Acorn BBC Microcomputer. It was shipped as a ROM to be inserted onto the BBC Micro's motherboard. It has an extremely limited design, and uses a flat directory structure...

    (DFS) This was an optional component for the BBC Micro
    BBC Micro
    The BBC Microcomputer System, or BBC Micro, was a series of microcomputers and associated peripherals designed and built by Acorn Computers for the BBC Computer Literacy Project, operated by the British Broadcasting Corporation...

    , offered as a kit with a disk controller chip, a ROM chip, and a handful of logic chips, to be installed inside the computer. See also Advanced Disc Filing System
    Advanced Disc Filing System
    The Advanced Disc Filing System is a computing file system particular to the Acorn computer range and RISC OS based successors. Initially based on the rare Acorn Winchester Filing System, it was renamed to the Advanced Disc Filing System when support for floppy discs was added and on later 32 bit...

    .
  • AMSDOS
    AMSDOS
    AMSDOS is a disk operating system for the 8-bit Amstrad CPC Computer . The name is a contraction of Amstrad Disc Operating System....

    , for the Amstrad CPC
    Amstrad CPC
    The Amstrad CPC is a series of 8-bit home computers produced by Amstrad between 1984 and 1990. It was designed to compete in the mid-1980s home computer market dominated by the Commodore 64 and the Sinclair ZX Spectrum, where it successfully established itself primarily in the United Kingdom,...

     computers.
  • GDOS and G+DOS, for the +D
    +D
    The +D was a floppy disk and printer interface for the Sinclair ZX Spectrum home computer, developed as a successor to Miles Gordon Technology's earlier product, the DISCiPLE...

     and DISCiPLE
    DISCiPLE
    The DISCiPLE was a floppy disk interface for the Sinclair ZX Spectrum home computer. Designed by Miles Gordon Technology, it was marketed by Rockfort Products and launched in 1986....

     disk interfaces for the ZX Spectrum
    ZX Spectrum
    The ZX Spectrum is an 8-bit personal home computer released in the United Kingdom in 1982 by Sinclair Research Ltd...

    .

Disk operating systems that were the main OS

Some disk operating systems were the operating system for the entire computer system.
  • The DOS/360
    DOS/360
    Disk Operating System/360, also DOS/360, or simply DOS, was an operating system for IBM mainframes. It was announced by IBM on the last day of 1964, and it was first delivered in June 1966....

    initial/simple operating system for the IBM
    IBM
    International Business Machines Corporation or IBM is an American multinational technology and consulting corporation headquartered in Armonk, New York, United States. IBM manufactures and sells computer hardware and software, and it offers infrastructure, hosting and consulting services in areas...

     System/360
    System/360
    The IBM System/360 was a mainframe computer system family first announced by IBM on April 7, 1964, and sold between 1964 and 1978. It was the first family of computers designed to cover the complete range of applications, from small to large, both commercial and scientific...

     family of mainframe computer
    Mainframe computer
    Mainframes are powerful computers used primarily by corporate and governmental organizations for critical applications, bulk data processing such as census, industry and consumer statistics, enterprise resource planning, and financial transaction processing.The term originally referred to the...

    s (it later became DOS/VSE, and was eventually just called VSE).
  • The DOS operating system for DEC
    Digital Equipment Corporation
    Digital Equipment Corporation was a major American company in the computer industry and a leading vendor of computer systems, software and peripherals from the 1960s to the 1990s...

     PDP-11
    PDP-11
    The PDP-11 was a series of 16-bit minicomputers sold by Digital Equipment Corporation from 1970 into the 1990s, one of a succession of products in the PDP series. The PDP-11 replaced the PDP-8 in many real-time applications, although both product lines lived in parallel for more than 10 years...

     minicomputer
    Minicomputer
    A minicomputer is a class of multi-user computers that lies in the middle range of the computing spectrum, in between the largest multi-user systems and the smallest single-user systems...

    s. This OS and the computers it ran on were nearly obsolete by the time PCs became common, with various descendants and other replacements.
  • DOS for the IBM PC compatible
    IBM PC compatible
    IBM PC compatible computers are those generally similar to the original IBM PC, XT, and AT. Such computers used to be referred to as PC clones, or IBM clones since they almost exactly duplicated all the significant features of the PC architecture, facilitated by various manufacturers' ability to...

     platform
The best known family of operating systems named "DOS" is that running on IBM PC
IBM PC
The IBM Personal Computer, commonly known as the IBM PC, is the original version and progenitor of the IBM PC compatible hardware platform. It is IBM model number 5150, and was introduced on August 12, 1981...

s type hardware using the Intel CPUs or their compatible cousins from other makers. Any DOS in this family is usually just referred to as DOS
DOS
DOS, short for "Disk Operating System", is an acronym for several closely related operating systems that dominated the IBM PC compatible market between 1981 and 1995, or until about 2000 if one includes the partially DOS-based Microsoft Windows versions 95, 98, and Millennium Edition.Related...

. The original was 86-DOS, which would later become Microsoft
Microsoft
Microsoft Corporation is an American public multinational corporation headquartered in Redmond, Washington, USA that develops, manufactures, licenses, and supports a wide range of products and services predominantly related to computing through its various product divisions...

 MS-DOS
MS-DOS
MS-DOS is an operating system for x86-based personal computers. It was the most commonly used member of the DOS family of operating systems, and was the main operating system for IBM PC compatible personal computers during the 1980s to the mid 1990s, until it was gradually superseded by operating...

. It was also licensed to IBM by Microsoft, and marketed by them as PC-DOS
PC-DOS
IBM PC DOS is a DOS system for the IBM Personal Computer and compatibles, manufactured and sold by IBM from the 1980s to the 2000s....

. Digital Research
Digital Research
Digital Research, Inc. was the company created by Dr. Gary Kildall to market and develop his CP/M operating system and related products. It was the first large software company in the microcomputer world...

 produced a compatible variant known as DR DOS, which was eventually taken over (after a buyout of Digital Research) by Novell
Novell
Novell, Inc. is a multinational software and services company. It is a wholly owned subsidiary of The Attachmate Group. It specializes in network operating systems, such as Novell NetWare; systems management solutions, such as Novell ZENworks; and collaboration solutions, such as Novell Groupwise...

, then by Caldera
Caldera (company)
Caldera was a US-based software company founded in 1994 to develop Linux- and DOS-based operating system products.- Caldera :Caldera, Inc...

. This became Novell DOS, then the open source OpenDOS, before being changed back to DR-DOS. There is also a free and open source
Free and open source software
Free and open-source software or free/libre/open-source software is software that is liberally licensed to grant users the right to use, study, change, and improve its design through the availability of its source code...

 version named FreeDOS
FreeDOS
FreeDOS is an operating system for IBM PC compatible computers. FreeDOS is made up of many different, separate programs that act as "packages" to the overall FreeDOS Project...

.
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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