Instructions on how to use the dir command. In Computing, dir (directory is a command used for file and directory listing specifically in the Command line interface

DOS is a family of closely related operating systems that dominated the IBM PC compatible market between 1981 and 1995 (or until about 2000, if one includes DOS-based Microsoft Windows versions (Windows 95, Windows 98, and Windows ME). An operating system (commonly abbreviated OS and O/S) is the software component of a Computer system that is responsible for the management and coordination IBM PC compatible computers are those generally similar to the original IBM PC, XT, and AT. Microsoft Windows is a series of Software Operating systems and Graphical user interfaces produced by Microsoft. Windows 95 is a consumer-oriented Graphical user interface -based Operating system. Windows 98 ( codenamed Memphis) is a graphical Operating system released on 25 June 1998 by Microsoft and the successor to Windows 95 Windows Millennium Edition, or Windows Me (IPA pronunciation, iː is a hybrid 16-bit / 32-bit graphical Operating system released on 14 September Related systems include MS-DOS, PC-DOS, DR-DOS (and Novell DOS and OpenDOS, which were based on DR-DOS), FreeDOS, PTS-DOS, ROM-DOS, JM-OS and several others. MS-DOS (short for M icro' s' oft D isk O perating S ystem is an Operating system commercialized by Microsoft. IBM PC-DOS is a DOS operating system for the IBM Personal Computer, sold throughout the 1980s and 1990s DR-DOS is a DOS -type Operating system for IBM PC - compatible Personal computers, originally developed by Gary Kildall DR-DOS is a DOS -type Operating system for IBM PC - compatible Personal computers, originally developed by Gary Kildall OpenDOS is a Freeware DOS -like and MS-DOS -compatible Operating system. FreeDOS (formerly Free-DOS and PD-DOS) is an Operating system for IBM PC compatible computers PTS-DOS is a Disk operating system, a DOS clone developed in Russia by PhysTechSoft.

All of these operating systems run on machines with the Intel x86 or compatible CPUs, mainly the IBM PC and compatibles. See also X86 assembly language The generic term x86 refers to the most commercially successful Instruction set architecture in the history of Personal IBM PC compatible computers are those generally similar to the original IBM PC, XT, and AT. Initially, DOS was not restricted to these, and machine-dependent versions of DOS and similar operating systems were produced for many non-IBM-compatible x86-based machines. See also X86 assembly language The generic term x86 refers to the most commercially successful Instruction set architecture in the history of Personal ^[1]

DOS is a single-user, single-task operating system with basic kernel functions that are non-reentrant code; once a process is begun, it must be allowed to run until finished before the same process can be used again. In Computer science, the kernel is the central component of most computer Operating systems (OS The DOS kernel provides various functions for programs, like displaying characters on-screen, reading a character from the keyboard, and accessing disk files.

In spite of the common usage, there has never been a microcomputer operating system called simply "DOS" (though there was a mainframe operating system in the 1960s). Disk Operating System/360, also DOS/360, or simply DOS, was an Operating system for IBM mainframes It was announced by IBM on the A number of unrelated, non-x86 microcomputer disk operating systems had "DOS" in their name, and are often referred to simply as "DOS" when discussing machines that use them (AmigaDOS, AMSDOS, ANDOS, Apple DOS, Atari DOS, Commodore DOS, CSI-DOS, ProDOS, TRS-DOS); but were incompatible with MS-DOS and PC-DOS EXE files. AmigaDOS provides the Disk operating system portion of the AmigaOS. AMSDOS is a Disk operating system for the 8-bit Amstrad CPC Computer (and various clones ANDOS is a Russian Operating system for Electronika BK-0010, Electronika BK-0011 and Electronika BK-0011M series computers Apple DOS refers to Operating systems for the Apple II series of microcomputers from 1979 through early 1983 Atari DOS is the Disk operating system used with the Atari 8-bit family of computers Commodore DOS, aka CBM DOS, was the Disk operating system used with Commodore 's 8-bit computers. CSI-DOS is an Operating system, created in Samara, for Soviet personal computers Elektronika BK-0011M and Elektronika BK-0011 ProDOS (the Professional Disk Operating System) became the most popular Operating system for the Apple II series of TRS-DOS (which stood for the T andy R adio S hack - D isk O perating S ystem was the Operating system for the

History

MS-DOS (and rebranded IBM PC-DOS which was licensed therefrom), and its predecessor, 86-DOS, were inspired by CP/M (Control Program / (for) Microcomputers) from Digital Research, which was the dominant disk operating system for 8-bit Intel 8080 and Zilog Z80 based microcomputers. IBM PC-DOS is a DOS operating system for the IBM Personal Computer, sold throughout the 1980s and 1990s 86-DOS was an operating system developed and marketed by Seattle Computer Products for its Intel 8086 -based computer kit CP/M (Control Program for Microcomputers is an Operating system originally created for Intel 8080 / 85 based Microcomputers by Gary Kildall Digital Research Inc (aka DR or DRI; originally Intergalactic Digital Research) was the company created by Dr The Intel 8080 was an early Microprocessor designed and manufactured by Intel. Zilog Inc, often seen as ZiLOG (the official company denotation in 1998 through Jun 2007 is a manufacturer of 8-bit, 16-bit, 24-bit The Zilog Z80 is an 8-bit Microprocessor designed and sold by Zilog from July 1976 onwards

IBM was introducing their first microcomputer, built with the Intel 8088 microprocessor, and needed an operating system. microcomputer is a Computer with a Microprocessor as its Central processing unit. The Intel 8088 is an Intel X86 Microprocessor based on the 8086, with 16- Bit registers and an 8-bit external Data bus In 1980, IBM initially approached Microsoft CEO Bill Gates (possibly believing that Microsoft owned CP/M due to the Microsoft Softcard, which allowed CP/M to run on an Apple II^[2] ). IBM was sent to Digital Research, and a meeting was set up. However, the initial negotiations for the use of CP/M broke down—Digital Research wished to sell CP/M on a royalty basis, while IBM sought a single license, and to change the name to "PC-DOS". DR founder Gary Kildall refused, and IBM withdrew. Gary Arlen Kildall (May 19 1942 – July 11 1994 was an American Computer scientist and Microcomputer Entrepreneur who created the CP/M ^[2]

IBM again approached Bill Gates. Gates approached Seattle Computer Company- there, Tim Paterson had developed a variant of CP/M-80, intended as an internal product for testing the SCP's new 16-bit 8086 CPU card for the S-100 bus. Tim Paterson (born 1956 is an American Computer programmer, best known as the original author of MS-DOS, the most widely used Operating system CP/M (Control Program for Microcomputers is an Operating system originally created for Intel 8080 / 85 based Microcomputers by Gary Kildall The 8086 is a 16-bit Microprocessor chip designed by Intel and introduced on the market in 1978 which gave rise to the X86 architecture The S-100 bus, IEEE696 -1983 (withdrawn, was an early Computer bus designed in 1974 as a part of the Altair 8800, generally considered today The system was initially named "QDOS" (Quick and Dirty Operating System), before being made commercially available as 86-DOS. 86-DOS was an operating system developed and marketed by Seattle Computer Products for its Intel 8086 -based computer kit Microsoft purchased 86-DOS, allegedly for $50,000. This became Microsoft Disk Operating System, MS-DOS, introduced in 1981. ^[3]

Microsoft also licensed their system to multiple computer companies, who supplied MS-DOS for their own hardware and sometimes under their own names. Microsoft later required the use of the MS-DOS name, with the exception of the IBM variant. IBM continued to develop their version, PC-DOS, for the IBM PC. IBM PC-DOS is a DOS operating system for the IBM Personal Computer, sold throughout the 1980s and 1990s The PC used the Intel 8088 CPU, which used the same instruction set as the 8086. The Intel 8088 is an Intel X86 Microprocessor based on the 8086, with 16- Bit registers and an 8-bit external Data bus ^[3] Digital Research became aware that an operating system similar to CP/M was being sold by IBM (under the same name that IBM insisted upon for CP/M), and threatened legal action. IBM responded by offering an agreement: they would give PC consumers a choice of PC-DOS or CP/M-86, Kildall's 8086 version. CP/M-86 was a version of the CP/M operating system that Digital Research made for the Intel 8086 and Intel 8088. CP/M cost almost $200 more than PC-DOS, however, and sales were low. CP/M faded, with MS-DOS and PC-DOS becoming the marketed operating system for PCs and PC compatibles. ^[2]

Digital Research attempted to regain the market lost from CP/M-86 with DR-DOS, compatible with both MS-DOS and CP/M-86 software. DR-DOS is a DOS -type Operating system for IBM PC - compatible Personal computers, originally developed by Gary Kildall Digital Research was later bought by Novell, and DR DOS became Novell DOS 7, and later became part of Caldera (as OpenDOS and DR DOS 7), Lineo, and DeviceLogics. Novell Inc ( is a global Software Corporation based in the United States specializing in enterprise operating systems such as SUSE OpenDOS is a Freeware DOS -like and MS-DOS -compatible Operating system.

Microsoft and IBM later had a series of disagreements over two successor operating systems to DOS- Microsoft's Windows and IBM's OS/2. OS/2 is a computer Operating system, initially created by Microsoft and IBM, then later developed by IBM exclusively ^[4] They split development of their DOS systems as a result. ^[5] MS-DOS was partially transformed into Windows; the last version of PC-DOS was PC-DOS 2000, released in 1998.

The FreeDOS project began June 26, 1994, when Microsoft announced it would no longer sell or support MS-DOS. Jim Hall then posted a manifesto proposing the development of an open-source replacement. Within a few weeks, other programmers including Pat Villani and Tim Norman joined the project. A kernel, the command. com command line interpreter (shell) and core utilities were created by pooling code they had written or found available. There were several official pre-release distributions of FreeDOS before the FreeDOS 1. 0 distribution was released on September 3, 2006. FreeDOS does not require license fees or royalties^[6].

The only other DOS-type systems that are actively distributed now are Enhanced DR-DOS, the Russian PTS-DOS, and embeddable ROM-DOS. Enhanced DR-DOS is a patch kit to update release 701 of OpenDOS, a derivative of DR-DOS made available as Source code by Caldera PTS-DOS is a Disk operating system, a DOS clone developed in Russia by PhysTechSoft. Only one commercially available DOS system is sold, DR-DOS.

Since 2005, there is a 100% GPL licensed version of DOS, called NX-DOS. Currently under development, 16-bit, real-time, networkable, boots from a floppy, and has an incomplete USB driver. Started on 1992 as a personal project, it was released as GPL on 2005 ^[7]

DOS and Microsoft Windows

Early versions of Microsoft Windows were an application that ran on top of a separate version of DOS. Microsoft Windows is a series of Software Operating systems and Graphical user interfaces produced by Microsoft. With Windows for Workgroups 3.11, DOS was essentially reduced to the role of a boot loader for the Windows kernel. Windows 31x was a major release of Microsoft Windows. Several editions were released between 1992 and 1994 succeeding Windows 3

With Windows 95, 98, and ME, MS-DOS is included as the boot loader rather than being sold separately. With Windows 95 and 98, but not ME, the MS-DOS component could be run without starting Windows. Often, Windows 9x can be loaded as a version of DOS despite saying "Loading Windows" in lieu of the typical loading message.

The true 32-bit versions of Windows starting with NT and including 2003, XP, and Vista, run entirely independent of DOS. Most versions include a DOS subsystem, NTVDM, that runs a modified version of MS-DOS 5. Virtual DOS machine (VDM is Microsoft 's technology that allows running legacy MS-DOS and 16-bit Windows programs on Intel 80386 or higher computers 0 in a virtual machine for the purpose of running DOS software and Windows command-line programs of similar appearance which are not compatible with true MS-DOS.

Versions

See Comparison of x86 DOS operating systems for a timeline and comparison of versions. This article details various versions of DOS -compatible operating systems

Operations

Accessing hardware under DOS

The operating system offers a hardware abstraction layer that allows development of character-based applications, but not for accessing most of the hardware, such as graphics cards, printers, or mice. A hardware abstraction layer ( HAL) is an Abstraction layer, implemented in software between the physical hardware of a Computer and Typical PC hardware A typical Personal computer consists of a case or chassis in a tower shape (desktop and the following parts Motherboard A video card, also known as a graphics accelerator card, display adapter, or graphics card, is a hardware component whose function is to In Computing, a mouse (plural mice, mouse devices, or mouses) This required programmers to access the hardware directly, resulting in each application having its own set of device drivers for each hardware peripheral. In computing a device driver or software driver is a Computer program allowing higher-level computer programs to interact with a Hardware device Hardware manufacturers would release specifications to ensure device drivers for popular applications were available.

Reserved device names under DOS

There are reserved device names in DOS that cannot be used as filenames regardless of extension; these restrictions also affect several Windows versions, in some cases causing crashes and security vulnerabilities.

A partial list of these reserved names is: NUL:, COM1: or AUX:, COM2:, COM3:, COM4:, CON:, LPT1: or PRN:, LPT2:, LPT3:, and CLOCK$.

More recent versions of both MS-DOS and IBM-DOS allow reserved device names without the trailing colon; e. g. , PRN refers to PRN:.

The NUL filename redirects to a null file, similar in function to the UNIX device /dev/null. In Unix-like Operating systems /dev/null or the null device is a Special file that discards all data written to it (but reports that It is best suited for being used in batch command files to discard unneeded output. If NUL is copied to a file that already exists, it will truncate the target file; otherwise, a zero byte file will be created. (Thus, copy NUL foo is functionally similar to the UNIX commands cat </dev/null >foo and cp /dev/null foo. ) Naming a file as NUL, regardless of extension, could cause unpredictable behavior in most applications. Well-designed applications will generate an error stating that NUL is a DOS reserved filename; others generate the file but whatever the program saves is lost; finally, some applications may hang or leave the computer in an inconsistent state, requiring a reboot. In Computing, booting ( booting up) is a bootstrapping process that starts Operating systems when the user turns on a Computer system

Drive naming scheme

Main article: Drive letter assignment

Under Microsoft's DOS operating system and its derivatives drives are referred to by identifying letters. Drive letter assignment is the process of assigning alphabetical identifiers to physical or logical Disk drives or partitions (drive volumes in the root Filesystem An operating system (commonly abbreviated OS and O/S) is the software component of a Computer system that is responsible for the management and coordination Standard practice is to reserve "A" and "B" for floppy drives. A floppy disk is an increasingly Obsolete data storage medium that is composed of a disk of thin flexible ("floppy" Magnetic storage medium encased On systems with only one floppy drive DOS permits the use of both letters for one drive, and DOS will ask to swap disks. This permits copying from floppy to floppy or having a program run from one floppy while having its data on another. Hard drives were originally assigned the letters "C" and "D". A hard disk drive ( HDD) commonly referred to as a hard drive, hard disk, or fixed disk drive, is a Non-volatile storage device DOS could only support one active partition per drive. As support for more hard drives became available, this developed into assigning the active primary partition on each drive letters first, then making a second pass over the drives to allocate letters to logical drives in the extended partition, then making a third, which gives the other non-active primary partitions their names. Disk partitioning is the creation of separate divisions of a Hard disk drive using Partition editors Once a disk is divided into several partitions directories and An Extended Boot Record (EBR or Extended Partition Boot Record (EPBR is a descriptor for a logical partition under the common DOS disk drive partitioning system Disk partitioning is the creation of separate divisions of a Hard disk drive using Partition editors Once a disk is divided into several partitions directories and (Always assumed, they exist and contain a DOS-readable file system. ) Lastly, DOS allocate letters for optical disc drives, RAM disks, and other hardware. In Computing, an optical disc drive ( ODD) is a Disk drive that uses Laser light or electromagnetic waves near the Light spectrum A RAM disk is a software layer that enables applications to transparently use RAM, often a segment of Main memory, as if it was a Hard disk Letter assignments usually occur in the order of the drivers loaded, but the drivers can instruct DOS to assign a different letter. An example is network drives, for which the driver will assign letters nearer the end of the alphabets.

Because DOS applications use these drive letters directly (unlike the /dev directory in Unix-like systems), they can be disrupted by adding new hardware that needs a drive letter. A Unix-like (sometimes shortened to *nix) Operating system is one that behaves in a manner similar to a Unix system while not necessarily conforming An example is the addition of a new hard drive with a primary partition to an original hard drive that contains logical drives in extended partitions. As primary partitions have higher priority than the logical drives, it will change drive letters in the configuration. Moreover, attempts to add a new hard drive with only logical drives in an extended partition would still disrupt the letters of RAM disks and optical drives. This problem persisted through the 9x versions of Windows until NT, which preserves the letters of existing drives until the user changes it.

The DOS boot sequence

The boot information for PC-compatible computers is located at track zero. In DOS, this code will read the DOS BIOS into memory and execute it. In Computing, the BIOS (ˈbaɪoʊs The BIOS is located in IBMBIO.COM on DR DOS and PC DOS, and IO.SYS on MS DOS. IBMBIOCOM is a filename used by the Boot loader for several DOS operating systems IOSYS is an essential part of MS-DOS and Windows 9x. It contains the default MS-DOS Device drivers (hardware interfacing routines and the DOS initialization The BIOS will then load the DOS kernel, located in IBMDOS.COM (PC DOS or DR DOS) or MSDOS.SYS (MS DOS). IBMDOSCOM is the filename of the DOS kernel. It exists in DR-DOS and PC-DOS systems with MS-DOS using MSDOS MSDOSSYS an important system file on MS-DOS and Windows 9x systems In the Windows DOS versions (MS DOS 7 and 8), the BIOS and kernel are combined in IO. SYS, and MSDOS. SYS is a text configuration file.

The kernel then executes the CONFIG.SYS file. CONFIGSYS is the primary Configuration file for the DOS and OS/2 Operating systems It is a special file that contains setup or configuration In CONFIG. SYS, the SHELL command specifies the location of the shell (typically COMMAND.COM). COMMANDCOM is the filename of the default Operating system shell for DOS Operating systems and the default Command line interpreter The shell will then launch, and open a startup batch file (typically AUTOEXEC.BAT)

DOS emulators

DOSBox running in Linux

Under Linux it is possible to run copies of DOS and many of its clones under DOSEMU, a Linux-native virtual machine for running real mode programs. AUTOEXECBAT is the name of a system file found originally on the MS-DOS operating system Linux (commonly pronounced ˈlɪnəks DOSEMU, alternatively rendered dosemu, is a Compatibility layer software package that enables MS-DOS systems DOS clones such as FreeDOS, and In Computer science, a virtual machine (VM is a Software implementation of a machine (computer that executes programs like a real machine Real mode, also called real address mode, is an operating mode of 80286 and later X86 -compatible CPUs. There are a number of other emulators for running DOS under various versions of UNIX, even on non-x86 platforms, such as DOSBox. An emulator duplicates (provides an emulation of the functions of one System using a different system so that the second system behaves like (and appears to See also X86 assembly language The generic term x86 refers to the most commercially successful Instruction set architecture in the history of Personal DOSBox is an Emulator which simulates a computer running MS-DOS.

DOS emulators are gaining popularity among Windows XP users because this system is incompatible with pure DOS. Windows XP is a family of 32-bit and 64-bit Operating systems produced by Microsoft for use on Personal computers including home and They can be used to run software (often 'abandonware') made for DOS. Abandonware refers to Computer software that is no longer sold or supported or whose Copyright ownership may be unclear for various reasons One of the most famous emulators is DOSBox, designed for game-playing on modern operating systems. DOSBox is an Emulator which simulates a computer running MS-DOS. ^[8] Another emulator Tao ExDOS is designed for business & printing solutions. VDMSound is also popular on Windows XP for its GUI and sound support. VDMSound is an Open source (licensed under the GPL) Emulator of legacy Sound card devices for Microsoft Windows, designed to allow

It is possible to run DOS applications under a Virtual PC environment, allowing better compatibility than DOS emulators as a legitimate version of MS-DOS can be installed which should allow all but the most stubborn applications to run^[9]. Microsoft Virtual PC is a Virtualization suite for Microsoft Windows Operating systems and an Emulation suite for

References

See also

• COMMAND.COM, the command line interpreter for DOS and Windows 9x
• MS-DOS API
• MS-DOS
• IBM PC-DOS
• DR-DOS
• FreeDOS
• ROM-DOS

External links

• MS-DOS Reference — Not just for MS-DOS but also for other DOSses on the PC platform. COMMANDCOM is the filename of the default Operating system shell for DOS Operating systems and the default Command line interpreter Windows 9x is the family of Microsoft Windows Operating systems that comprises the hybrid 16/32-bit Windows versions Windows 95, Windows 98 The MS-DOS API is an API used originally in MS-DOS / PC-DOS, and later by other DOS systems MS-DOS (short for M icro' s' oft D isk O perating S ystem is an Operating system commercialized by Microsoft. IBM PC-DOS is a DOS operating system for the IBM Personal Computer, sold throughout the 1980s and 1990s DR-DOS is a DOS -type Operating system for IBM PC - compatible Personal computers, originally developed by Gary Kildall FreeDOS (formerly Free-DOS and PD-DOS) is an Operating system for IBM PC compatible computers MS-DOS (short for M icro' s' oft D isk O perating S ystem is an Operating system commercialized by Microsoft. IBM PC compatible computers are those generally similar to the original IBM PC, XT, and AT.
• DOS and Windows timeline