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127-430: Function keys on a terminal may either generate short fixed sequences of characters, often beginning with the escape character ( ASCII 27), or the characters they generate may be configured by sending special character sequences to the terminal. On a standard computer keyboard, the function keys may generate a fixed, single byte code, outside the normal ASCII range, which is translated into some other configurable sequence by

254-458: A relocatable format using the filename extension .CMD to avoid name conflicts with CP/M-80 and MS-DOS .COM files. MS-DOS version 1.0 added a more advanced relocatable . EXE executable file format. Most of the machines in the early days of MS-DOS had differing system architectures and there was a certain degree of incompatibility, and subsequently vendor lock-in . Users who began using MS-DOS with their machines were compelled to continue using

381-529: A shift function (like in ITA2 ), which would allow more than 64 codes to be represented by a six-bit code . In a shifted code, some character codes determine choices between options for the following character codes. It allows compact encoding, but is less reliable for data transmission , as an error in transmitting the shift code typically makes a long part of the transmission unreadable. The standards committee decided against shifting, and so ASCII required at least

508-618: A 1994 settlement agreement limiting Microsoft to per-copy licensing. Digital Research did not gain by this settlement, and years later its successor in interest, Caldera , sued Microsoft for damages in the Caldera v. Microsoft lawsuit. It was believed that the settlement ran in the order of $ 150 million , but was revealed in November 2009 with the release of the Settlement Agreement to be $ 280 million . Microsoft also used

635-530: A 2×5 matrix at the left of the keyboard; this was replaced by 12 keys in 3 blocks of 4 at the top of the keyboard in the Model M ("Enhanced", 1984). In the classic Mac OS , the function keys could be configured by the user, with the Function Keys control panel, to start a program or run an AppleScript . macOS assigns default functionality to (almost) all the function keys from F1 to F12 , but

762-522: A BS (backspace). Instead, there was a key marked RUB OUT that sent code 127 (DEL). The purpose of this key was to erase mistakes in a manually-input paper tape: the operator had to push a button on the tape punch to back it up, then type the rubout, which punched all holes and replaced the mistake with a character that was intended to be ignored. Teletypes were commonly used with the less-expensive computers from Digital Equipment Corporation (DEC); these systems had to use what keys were available, and thus

889-448: A DOS startup disk on Windows Vista , the files on the startup disk are dated April 18, 2005, but are otherwise unchanged, including the string "MS-DOS Version 8 Copyright 1981–1999 Microsoft Corp" inside COMMAND.COM . Windows 7, 8, and 8.1 can also create a MS-DOS startup disk. Starting with Windows 10 , the ability to create a MS-DOS startup disk has been removed, and so either a virtual machine running MS-DOS or an older version (in

1016-516: A Graphical User Interface (GUI) on top of MS-DOS. With Windows 95 , 98 , and Me , the role of MS-DOS was reduced to a boot loader according to Microsoft, with MS-DOS programs running in a virtual DOS machine within 32-bit Windows, with ability to boot directly into MS-DOS retained as a backward compatibility option for applications that required real mode access to the hardware, which was generally not possible within Windows. The command line accessed

1143-458: A character count followed by the characters of the line and which used EBCDIC rather than ASCII encoding. The Telnet protocol defined an ASCII "Network Virtual Terminal" (NVT), so that connections between hosts with different line-ending conventions and character sets could be supported by transmitting a standard text format over the network. Telnet used ASCII along with CR-LF line endings, and software using other conventions would translate between

1270-755: A copy of the Windows Me boot disk, stripped down to bootstrap only. This is accessible only by formatting a floppy as an "MS-DOS startup disk". Files like the driver for the CD-ROM support were deleted from the Windows Me bootdisk and the startup files ( AUTOEXEC.BAT and CONFIG.SYS ) no longer had content. This modified disk was the base for creating the MS-DOS image for Windows XP. Some of the deleted files can be recovered with an undelete tool. When booting up an MS-DOS startup disk made with Windows XP's format tool,

1397-432: A document or tab. F10 generally activates the menu bar , while ⇧ Shift + F10 activates a context menu . F2 is used in many Windows applications such as Windows Explorer, Excel, Visual Studio and other programs to access file or field edit functions, such as renaming a file. F4 is used in some applications to make the window "fullscreen", like in 3D Pinball: Space Cadet . In Microsoft IE, it

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1524-608: A few operating systems attempting to be compatible with MS-DOS, are sometimes referred to as "DOS" (which is also the generic acronym for disk operating system ). MS-DOS was the main operating system for IBM PC compatibles during the 1980s, from which point it was gradually superseded by operating systems offering a graphical user interface (GUI), in various generations of the graphical Microsoft Windows operating system. IBM licensed and re-released it in 1981 as PC DOS 1.0 for use in its PCs. Although MS-DOS and PC DOS were initially developed in parallel by Microsoft and IBM,

1651-541: A forceful letter to PC Week (November 5, 1990), denying that Microsoft was engaged in FUD tactics ("to serve our customers better, we decided to be more forthcoming about version 5.0") and denying that Microsoft copied features from DR DOS: "The feature enhancements of MS-DOS version 5.0 were decided and development was begun long before we heard about DR DOS 5.0. There will be some similar features. With 50 million MS-DOS users, it shouldn't be surprising that DRI has heard some of

1778-448: A higher price. Executable programs for CP/M-86 and MS-DOS were not interchangeable with each other; many applications were sold in both MS-DOS and CP/M-86 versions until MS-DOS became preponderant (later Digital Research operating systems could run both MS-DOS and CP/M-86 software). MS-DOS originally supported the simple .COM , which was modeled after a similar but binary-incompatible format known from CP/M-80 . CP/M-86 instead supported

1905-458: A large share of the business computer market. Microsoft and IBM together began what was intended as the follow-on to MS-DOS/PC DOS, called OS/2 . When OS/2 was released in 1987, Microsoft began an advertising campaign announcing that "DOS is Dead" and stating that version 4 was the last full release. OS/2 was designed for efficient multi-tasking and offered a number of advanced features that had been designed together with similar look and feel ; it

2032-498: A line terminator. The tty driver would handle the LF to CRLF conversion on output so files can be directly printed to terminal, and NL (newline) is often used to refer to CRLF in UNIX documents. Unix and Unix-like systems, and Amiga systems, adopted this convention from Multics. On the other hand, the original Macintosh OS , Apple DOS , and ProDOS used carriage return (CR) alone as

2159-605: A line terminator; however, since Apple later replaced these obsolete operating systems with their Unix-based macOS (formerly named OS X) operating system, they now use line feed (LF) as well. The Radio Shack TRS-80 also used a lone CR to terminate lines. Computers attached to the ARPANET included machines running operating systems such as TOPS-10 and TENEX using CR-LF line endings; machines running operating systems such as Multics using LF line endings; and machines running operating systems such as OS/360 that represented lines as

2286-416: A means of searching for the currently highlighted text elsewhere in a document. F5 is also commonly used as a reload key in many web browsers and other applications, while F11 activates the full screen/ kiosk mode on most browsers. Under the Windows environment, Alt + F4 is commonly used to quit an application; Ctrl + F4 will often close a portion of the application, such as

2413-407: A particular model), or per-copy (a fee for each copy of MS-DOS installed). The largest manufacturers used the per-processor arrangement, which had the lowest fee. This arrangement made it expensive for the large manufacturers to migrate to any other operating system, such as DR DOS. In 1991, the U.S. government Federal Trade Commission began investigating Microsoft's licensing procedures, resulting in

2540-600: A reserved device control (DC0), synchronous idle (SYNC), and acknowledge (ACK). These were positioned to maximize the Hamming distance between their bit patterns. ASCII-code order is also called ASCIIbetical order. Collation of data is sometimes done in this order rather than "standard" alphabetical order ( collating sequence ). The main deviations in ASCII order are: An intermediate order converts uppercase letters to lowercase before comparing ASCII values. ASCII reserves

2667-541: A reserved meaning. Over time this interpretation has been co-opted and has eventually been changed. In modern usage, an ESC sent to the terminal usually indicates the start of a command sequence, which can be used to address the cursor, scroll a region, set/query various terminal properties, and more. They are usually in the form of a so-called " ANSI escape code " (often starting with a " Control Sequence Introducer ", "CSI", " ESC [ ") from ECMA-48 (1972) and its successors. Some escape sequences do not have introducers, like

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2794-404: A seven-bit code. The committee considered an eight-bit code, since eight bits ( octets ) would allow two four-bit patterns to efficiently encode two digits with binary-coded decimal . However, it would require all data transmission to send eight bits when seven could suffice. The committee voted to use a seven-bit code to minimize costs associated with data transmission. Since perforated tape at

2921-513: A standard Microsoft kernel, which they would typically supply on disk to end users along with the hardware. Thus, there were many different versions of "MS-DOS" for different hardware, and there is a major distinction between an IBM-compatible (or ISA) machine and an MS-DOS [compatible] machine. Some machines, like the Tandy 2000 , were MS-DOS compatible but not IBM-compatible, so they could run software written exclusively for MS-DOS without dependence on

3048-399: A terminal. Some operating systems such as CP/M tracked file length only in units of disk blocks, and used control-Z to mark the end of the actual text in the file. For these reasons, EOF, or end-of-file , was used colloquially and conventionally as a three-letter acronym for control-Z instead of SUBstitute. The end-of-text character ( ETX ), also known as control-C , was inappropriate for

3175-602: A variety of other computers based on various other processors were in serious competition with the IBM PC: the Apple II , Mac , Commodore 64 and others did not use the 808x processor; many 808x machines of different architectures used custom versions of MS-DOS. At first all these machines were in competition. In time the IBM PC hardware configuration became dominant in the 808x market as software written to communicate directly with

3302-449: A variety of reasons, while using control-Z as the control character to end a file is analogous to the letter Z's position at the end of the alphabet, and serves as a very convenient mnemonic aid . A historically common and still prevalent convention uses the ETX character convention to interrupt and halt a program via an input data stream, usually from a keyboard. The Unix terminal driver uses

3429-450: A variety of tactics in MS-DOS and several of their applications and development tools that, while operating perfectly when running on genuine MS-DOS (and PC DOS), would break when run on another vendor's implementation of DOS. Notable examples of this practice included: All versions of Microsoft Windows have had an MS-DOS or MS-DOS-like command-line interface called MS-DOS Prompt which redirected input to MS-DOS and output from MS-DOS to

3556-456: A virtual machine or dual boot) must be used to format a floppy disk, or an image must be obtained from an external source. Other solutions include using DOS compatible alternatives, such as FreeDOS or even copying the required files and boot sector themselves. The last remaining components related to MS-DOS was the NTVDM component, which was removed entirely in Windows starting with Windows 11 as

3683-737: Is 0101 in binary). Many of the non-alphanumeric characters were positioned to correspond to their shifted position on typewriters; an important subtlety is that these were based on mechanical typewriters, not electric typewriters. Mechanical typewriters followed the de facto standard set by the Remington No. 2 (1878), the first typewriter with a shift key, and the shifted values of 23456789- were "#$ %_&'()  – early typewriters omitted 0 and 1 , using O (capital letter o ) and l (lowercase letter L ) instead, but 1! and 0) pairs became standard once 0 and 1 became common. Thus, in ASCII !"#$ % were placed in

3810-412: Is mainly for education and experimentation with historic operating systems and for new programmers to gain an understanding of how low-level software works, both historic and current. According to program manager Rich Turner, the other versions could not be open-sourced due to third-party licensing restrictions. Due to the historical nature of the software, Microsoft will not accept any pull requests to

3937-518: Is often called the MS-DOS Prompt. In part, this was the official name for it in Windows 9x and early versions of Windows NT (NT 3.5 and earlier), and in part because the SoftPC emulation of DOS redirects output into it. Actually only COMMAND.COM and other 16-bit commands run in an NTVDM with AUTOEXEC.NT and CONFIG.NT initialization determined by _DEFAULT.PIF , optionally permitting

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4064-427: Is replaced by a second control-S to resume output. The 33 ASR also could be configured to employ control-R (DC2) and control-T (DC4) to start and stop the tape punch; on some units equipped with this function, the corresponding control character lettering on the keycap above the letter was TAPE and TAPE respectively. The Teletype could not move its typehead backwards, so it did not have a key on its keyboard to send

4191-441: Is still used in embedded x86 systems due to its simple architecture and minimal memory and processor requirements, though some current products have switched to the still-maintained open-source alternative FreeDOS . In 2018, Microsoft released the source code for MS-DOS 1.25 and 2.0 on GitHub , with the source code for MS-DOS 4.00 being released in the same repository six years later. The purpose of this, according to Microsoft,

4318-404: Is the newline problem on various operating systems . Teletype machines required that a line of text be terminated with both "carriage return" (which moves the printhead to the beginning of the line) and "line feed" (which advances the paper one line without moving the printhead). The name "carriage return" comes from the fact that on a manual typewriter the carriage holding the paper moves while

4445-618: Is used to view the URL list of previously viewed websites. Other function key assignments common to all Microsoft Office applications are: F7 to check spelling, Alt + F8 to call the macros dialog, Alt + F11 to call the Visual Basic Editor and ⇧ Shift + Alt + F11 to call the Script Editor. In Microsoft Word, ⇧ Shift + F1 reveals formatting. In Microsoft PowerPoint, F5 starts

4572-558: The F8 key was used alone. ASCII ASCII ( / ˈ æ s k iː / ASS -kee ), an acronym for American Standard Code for Information Interchange , is a character encoding standard for electronic communication. ASCII codes represent text in computers, telecommunications equipment , and other devices. ASCII has just 128 code points , of which only 95 are printable characters , which severely limit its scope. The set of available punctuation had significant impact on

4699-600: The BIOS interface. Generally during the power-on self-test , BIOS access can be gained by hitting either a function key or the Del key. In the BIOS keys can have different purposes depending on the BIOS. However, F10 is the de facto standard for save and exit which saves all changes and restarts the system. During Windows 10 startup, ⇧ Shift + F8 is used to enter safe mode ; in legacy versions of Microsoft Windows ,

4826-503: The Comité Consultatif International Téléphonique et Télégraphique (CCITT) International Telegraph Alphabet No. 2 (ITA2) standard of 1932, FIELDATA (1956 ), and early EBCDIC (1963), more than 64 codes were required for ASCII. ITA2 was in turn based on Baudot code , the 5-bit telegraph code Émile Baudot invented in 1870 and patented in 1874. The committee debated the possibility of

4953-533: The F-111D (first ordered 1967, delivered 1970–1973). In computing use, they were found on the HP 9810A calculator (1971) and later models of the HP 9800 series , which featured 10 programmable keys in 5×2 block (2 rows of 5 keys) at the top left of the keyboard, with paper labels. The HP 9830A (1972) was an early desktop computer, and one of the earliest specifically computing uses. HP continued its use of function keys in

5080-466: The HP 2640 (1975), which used screen-labeled function keys , placing the keys close to the screen, where labels could be displayed for their function. NEC 's PC-8001 , introduced in 1979, featured five function keys at the top of the keyboard, along with a numeric keypad on the right-hand side of the keyboard. Their modern use may have been popularized by IBM keyboards: first the IBM 3270 terminals, then

5207-586: The IBM PC . IBM use of function keys dates to the IBM 3270 line of terminals, specifically the IBM 3277 (1972) with 78-key typewriter keyboard or operator console keyboard version, which both featured 12 programmed function (PF) keys in a 3×4 matrix at the right of the keyboard. Later models replaced this with a numeric keypad , and moved the function keys to 24 keys at the top of the keyboard. The original IBM PC keyboard ( PC/XT , 1981) had 10 function keys (F1–F10) in

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5334-591: The Intel 8086 and 8088 processors, including the IBM PC and clones, the initial competition to the PC DOS/MS-DOS line came from Digital Research , whose CP/M operating system had inspired MS-DOS. In fact, there remains controversy as to whether QDOS was more or less plagiarized from early versions of CP/M code. Digital Research released CP/M-86 a few months after MS-DOS, and it was offered as an alternative to MS-DOS and Microsoft's licensing requirements, but at

5461-581: The Santa Cruz Operation (SCO). On March 25, 2014, Microsoft made the code to SCP MS-DOS 1.25 and a mixture of Altos MS-DOS 2.11 and TeleVideo PC DOS 2.11 available to the public under the Microsoft Research License Agreement , which makes the code source-available , but not open source as defined by Open Source Initiative or Free Software Foundation standards. Microsoft would later re-license

5588-584: The Teletype Model 33 , which used the left-shifted layout corresponding to ASCII, differently from traditional mechanical typewriters. Electric typewriters, notably the IBM Selectric (1961), used a somewhat different layout that has become de facto standard on computers – following the IBM PC (1981), especially Model M (1984) – and thus shift values for symbols on modern keyboards do not correspond as closely to

5715-730: The United States Federal Government support ASCII, stating: I have also approved recommendations of the Secretary of Commerce [ Luther H. Hodges ] regarding standards for recording the Standard Code for Information Interchange on magnetic tapes and paper tapes when they are used in computer operations. All computers and related equipment configurations brought into the Federal Government inventory on and after July 1, 1969, must have

5842-739: The Windows NT -derived 32-bit operating systems ( Windows NT , 2000 , XP and newer), developed alongside the 9x series, do not contain MS-DOS compatibility as a core component of the operating system nor do they rely on it for bootstrapping, as NT was not with the level of support for legacy MS-DOS and Win16 apps that Windows 9x was, but does provide limited DOS emulation called NTVDM (NT Virtual DOS Machine) to run DOS applications and provide DOS-like command prompt windows. 64-bit versions of Windows NT prior to Windows 11 (and Windows Server 2008 R2 by extension) do not provide DOS emulation and cannot run DOS applications natively. Windows XP contains

5969-667: The carriage return , line feed , and tab codes. For example, lowercase i would be represented in the ASCII encoding by binary 1101001 = hexadecimal 69 ( i is the ninth letter) = decimal 105. Despite being an American standard, ASCII does not have a code point for the cent (¢). It also does not support English terms with diacritical marks such as résumé and jalapeño , or proper nouns with diacritical marks such as Beyoncé (although on certain devices characters could be combined with punctuation such as Tilde (~) and Backtick (`) to approximate such characters.) The American Standard Code for Information Interchange (ASCII)

6096-645: The "Reset to Initial State", "RIS" command " ESC c ". In contrast, an ESC read from the terminal is most often used as an out-of-band character used to terminate an operation or special mode, as in the TECO and vi text editors . In graphical user interface (GUI) and windowing systems, ESC generally causes an application to abort its current operation or to exit (terminate) altogether. The inherent ambiguity of many control characters, combined with their historical usage, created problems when transferring "plain text" files between systems. The best example of this

6223-533: The "help" prefix command in GNU Emacs . Many more of the control characters have been assigned meanings quite different from their original ones. The "escape" character (ESC, code 27), for example, was intended originally to allow sending of other control characters as literals instead of invoking their meaning, an "escape sequence". This is the same meaning of "escape" encountered in URL encodings, C language strings, and other systems where certain characters have

6350-401: The "line feed" function (which causes a printer to advance its paper), and character 8 represents " backspace ". RFC   2822 refers to control characters that do not include carriage return, line feed or white space as non-whitespace control characters. Except for the control characters that prescribe elementary line-oriented formatting, ASCII does not define any mechanism for describing

6477-748: The "pre-announcement" of MS-DOS 6.0 again stifled the sales of DR DOS. Microsoft had been accused of carefully orchestrating leaks about future versions of MS-DOS in an attempt to create what in the industry is called FUD ( fear, uncertainty, and doubt ) regarding DR DOS. For example, in October 1990, shortly after the release of DR DOS 5.0, and long before the eventual June 1991 release of MS-DOS 5.0, stories on feature enhancements in MS-DOS started to appear in InfoWorld and PC Week . Brad Silverberg , then Vice President of Systems Software at Microsoft and general manager of its Windows and MS-DOS Business Unit, wrote

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6604-451: The 1994 release of MS-DOS 6.21, which had disk compression removed. Shortly afterwards came version 6.22, with a new version of the disk compression system, DriveSpace, which had a different compression algorithm to avoid the infringing code. Prior to 1995, Microsoft licensed MS-DOS (and Windows) to computer manufacturers under three types of agreement: per-processor (a fee for each system the company sold), per-system (a fee for each system of

6731-408: The 2007 model), the volume controls are located on function keys F10 to F12 where they are mapped to various functions . Any recent version of Mac OS X or macOS is able to detect which generation of Apple keyboard is being used, and to assign proper default actions corresponding to the labels shown on this Apple keyboard (provided that this keyboard was manufactured before the release of

6858-419: The ASCII chart in this article. Ninety-five of the encoded characters are printable: these include the digits 0 to 9 , lowercase letters a to z , uppercase letters A to Z , and punctuation symbols . In addition, the original ASCII specification included 33 non-printing control codes which originated with Teletype models ; most of these are now obsolete, although a few are still commonly used, such as

6985-679: The ASCII table as earlier keyboards did. The /? pair also dates to the No. 2, and the ,< .> pairs were used on some keyboards (others, including the No. 2, did not shift , (comma) or . (full stop) so they could be used in uppercase without unshifting). However, ASCII split the ;: pair (dating to No. 2), and rearranged mathematical symbols (varied conventions, commonly -* =+ ) to :* ;+ -= . Some then-common typewriter characters were not included, notably ½ ¼ ¢ , while ^ ` ~ were included as diacritics for international use, and < > for mathematical use, together with

7112-470: The DEL character was assigned to erase the previous character. Because of this, DEC video terminals (by default) sent the DEL character for the key marked "Backspace" while the separate key marked "Delete" sent an escape sequence ; many other competing terminals sent a BS character for the backspace key. The early Unix tty drivers, unlike some modern implementations, allowed only one character to be set to erase

7239-561: The DOS command line (usually COMMAND.COM ) through a Windows module (WINOLDAP.MOD). Windows NT-based operating systems boot to a kernel whose purpose is to load Windows and run the system. One cannot run Win32 applications in the loader system in the manner that OS/2, UNIX or consumer versions of Windows can launch character-mode sessions. The command session permits running various supported command-line utilities from Win32, MS-DOS, OS/2 1.x and POSIX. The emulators for MS-DOS, OS/2 and POSIX use

7366-535: The Flexowriter could be used as a computer terminal , this electromechanical typewriter was primarily intended as a stand-alone word processing system. The interpretation of the function keys was determined by the programming of a plugboard inside the back of the machine. Soft keys date to avionics multi-function displays of military planes of the late 1960s/early 1970s, such as the Mark II avionics of

7493-423: The IBM 5150 or the IBM PC . Within a year, Microsoft licensed MS-DOS to over 70 other companies. It was designed to be an OS that could run on any 8086-family computer. Each computer would have its own distinct hardware and its own version of MS-DOS, similar to the situation that existed for CP/M , and with MS-DOS emulating the same solution as CP/M to adapt for different hardware platforms. To this end, MS-DOS

7620-470: The MS-DOS Prompt, or, in later versions, Command Prompt . This could run many DOS and variously Win32, OS/2 1.x and POSIX command-line utilities in the same command-line session, allowing piping between commands. The user interface, and the icon up to Windows 2000, followed the native MS-DOS interface. The Command Prompt introduced with Windows NT is not actually MS-DOS, but shares some commands with MS-DOS. The 16-bit versions of Windows (up to 3.11) ran as

7747-434: The MS-DOS name for all versions but the IBM one, which was originally called "IBM Personal Computer DOS", later shortened to IBM PC DOS . (Competitors released compatible DOS systems such as DR-DOS and PTS-DOS that could also run MS-DOS applications.) In the former Eastern bloc , MS-DOS derivatives named DCP ( Disk Control Program  [ de ] ) 3.20 and 3.30 (DCP 1700, DCP 3.3) and WDOS existed in

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7874-405: The NTVDM and can therefore no longer natively run DOS or 16-bit Windows applications. There are alternatives such as virtual machine emulators such as Microsoft's own Virtual PC , as well as VMware , DOSBox etc., unofficial compatibility layers such as NTVDMx64, OTVDM (WineVDM), Win3mu and others. The introduction of Windows 3.0 in 1990, with an easy-to-use graphical user interface , marked

8001-597: The PC hardware without using standard operating system calls ran much faster, but on true PC-compatibles only. Non-PC-compatible 808x machines were too small a market to have fast software written for them alone, and the market remained open only for IBM PCs and machines that closely imitated their architecture, all running either a single version of MS-DOS compatible only with PCs, or the equivalent IBM PC DOS. Most clones cost much less than IBM-branded machines of similar performance, and became widely used by home users, while IBM PCs had

8128-469: The Teletype Model 33 machine assignments for codes 17 (control-Q, DC1, also known as XON), 19 (control-S, DC3, also known as XOFF), and 127 ( delete ) became de facto standards. The Model 33 was also notable for taking the description of control-G (code 7, BEL, meaning audibly alert the operator) literally, as the unit contained an actual bell which it rang when it received a BEL character. Because

8255-520: The Windows GUI; this capability was retained through Windows 98 Second Edition. Windows Me removed the capability to boot its underlying MS-DOS 8.0 alone from a hard disk, but retained the ability to make a DOS boot floppy disk (called an "Emergency Boot Disk") and can be hacked to restore full access to the underlying DOS. On December 31, 2001, Microsoft declared all versions of MS-DOS 6.22 and older obsolete and stopped providing support and updates for

8382-459: The actions assigned by default to these function keys have changed a couple of times over the history of Mac products and corresponding Mac OS X versions. As a consequence, the labels on Macintosh keyboards have changed over time to reflect the newer mappings of later Mac OS X versions: for instance, on a 2006 MacBook Pro, functions keys F3 , F4 and F5 are labelled for volume down/volume up, whereas on later MacBook Pros (starting with

8509-424: The background for loading Windows 9x . MS-DOS was a renamed form of 86-DOS  – owned by Seattle Computer Products , written by Tim Paterson . Development of 86-DOS took only six weeks, as it was basically a clone of Digital Research 's CP/M (for 8080/Z80 processors), ported to run on 8086 processors and with two notable differences compared to CP/M: an improved disk sector buffering logic, and

8636-496: The beginning of the end for the command-line driven MS-DOS. With the release of Windows 95 (and continuing in the Windows 9x product line through to Windows Me ), an integrated version of MS-DOS was used for bootstrapping , troubleshooting, and backwards-compatibility with old DOS software, particularly games, and no longer released as a standalone product. In Windows 95, the DOS, called MS-DOS 7, can be booted separately, without

8763-492: The capability to use the Standard Code for Information Interchange and the formats prescribed by the magnetic tape and paper tape standards when these media are used. MS-DOS MS-DOS ( / ˌ ɛ m ˌ ɛ s ˈ d ɒ s / em-es- DOSS ; acronym for Microsoft Disk Operating System , also known as Microsoft DOS ) is an operating system for x86 -based personal computers mostly developed by Microsoft . Collectively, MS-DOS, its rebranding as IBM PC DOS , and

8890-585: The change into its draft standard. The X3.2.4 task group voted its approval for the change to ASCII at its May 1963 meeting. Locating the lowercase letters in sticks 6 and 7 caused the characters to differ in bit pattern from the upper case by a single bit, which simplified case-insensitive character matching and the construction of keyboards and printers. The X3 committee made other changes, including other new characters (the brace and vertical bar characters), renaming some control characters (SOM became start of header (SOH)) and moving or removing others (RU

9017-666: The code under the MIT License on September 28, 2018, making these versions free software . Microsoft later released the code for MS-DOS 4.00 on April 25, 2024, under the same license. As an April Fool's Day joke in 2015, Microsoft Mobile launched a Windows Phone application called MS-DOS Mobile which was presented as a new mobile operating system and worked similar to MS-DOS. Microsoft licensed or released versions of MS-DOS under different names like Lifeboat Associates "Software Bus 86" a.k.a. SB-DOS , COMPAQ-DOS , NCR-DOS or Z-DOS before it eventually enforced

9144-493: The concept of "carriage return" was meaningless. IBM's PC DOS (also marketed as MS-DOS by Microsoft) inherited the convention by virtue of being loosely based on CP/M, and Windows in turn inherited it from MS-DOS. Requiring two characters to mark the end of a line introduces unnecessary complexity and ambiguity as to how to interpret each character when encountered by itself. To simplify matters, plain text data streams, including files, on Multics used line feed (LF) alone as

9271-527: The convention was so well established that backward compatibility necessitated continuing to follow it. When Gary Kildall created CP/M , he was inspired by some of the command line interface conventions used in DEC's RT-11 operating system. Until the introduction of PC DOS in 1981, IBM had no influence in this because their 1970s operating systems used EBCDIC encoding instead of ASCII, and they were oriented toward punch-card input and line printer output on which

9398-690: The default actions assigned by older versions of Mac OS X, which were Exposé and Dashboard). It can be noted that: Under MS-DOS , individual programs could decide what each function key meant to them, and the command line had its own actions. For example, F3 copied words from the previous command to the current command prompt. Following the IBM Common User Access guidelines, the F1 key gradually became universally associated with Help in most early Windows programs. To this day, Microsoft Office programs running in Windows list F1 as

9525-663: The earlier five-bit ITA2 , which was also used by the competing Telex teleprinter system. Bob Bemer introduced features such as the escape sequence . His British colleague Hugh McGregor Ross helped to popularize this work – according to Bemer, "so much so that the code that was to become ASCII was first called the Bemer–Ross Code in Europe". Because of his extensive work on ASCII, Bemer has been called "the father of ASCII". On March 11, 1968, US President Lyndon B. Johnson mandated that all computers purchased by

9652-576: The earlier teleprinter encoding systems. Like other character encodings , ASCII specifies a correspondence between digital bit patterns and character symbols (i.e. graphemes and control characters ). This allows digital devices to communicate with each other and to process, store, and communicate character-oriented information such as written language. Before ASCII was developed, the encodings in use included 26 alphabetic characters, 10 numerical digits , and from 11 to 25 special graphic symbols. To include all these, and control characters compatible with

9779-548: The end-of-transmission character ( EOT ), also known as control-D, to indicate the end of a data stream. In the C programming language , and in Unix conventions, the null character is used to terminate text strings ; such null-terminated strings can be known in abbreviation as ASCIZ or ASCIIZ, where here Z stands for "zero". Other representations might be used by specialist equipment, for example ISO 2047 graphics or hexadecimal numbers. Codes 20 hex to 7E hex , known as

9906-627: The first 32 code points (numbers 0–31 decimal) and the last one (number 127 decimal) for control characters . These are codes intended to control peripheral devices (such as printers ), or to provide meta-information about data streams, such as those stored on magnetic tape. Despite their name, these code points do not represent printable characters (i.e. they are not characters at all, but signals). For debugging purposes, "placeholder" symbols (such as those given in ISO 2047 and its predecessors) are assigned to them. For example, character 0x0A represents

10033-511: The host's window in the same way that Win16 applications use the Win32 explorer. Using the host's window allows one to pipe output between emulations. The MS-DOS emulation takes place through the NTVDM (NT Virtual DOS Machine). This is a modified SoftPC (a former product similar to VirtualPC ), running a modified MS-DOS 5 (NTIO.SYS and NTDOS.SYS). The output is handled by the console DLLs, so that

10160-751: The introduction of FAT12 instead of the CP/M filesystem . This first version was shipped in August 1980. Microsoft, which needed an operating system for the IBM Personal Computer , hired Tim Paterson in May 1981 and bought 86-DOS 1.10 for US$ 25,000 in July of the same year. Microsoft kept the version number, but renamed it MS-DOS. They also licensed MS-DOS 1.10/1.14 to IBM, which, in August 1981, offered it as PC DOS 1.0 as one of three operating systems for

10287-473: The key for Help in the Help menu. Internet Explorer in Windows does not list this keystroke in the help menu, but still responds with a help window. F3 is commonly used to activate a search function in applications, often cycling through results on successive presses of the key. ⇧ Shift + F3 is often used to search backwards. Some applications such as Visual Studio support Control + F3 as

10414-420: The keyboard device driver or interpreted directly by the application program. Function keys may have abbreviations or pictographic representations of default actions printed on/besides them, or they may have the more common "F-number" designations. The Singer/Friden 2201 Flexowriter Programmatic, introduced in 1965, had a cluster of 13 function keys, labeled F1 to F13 to the right of the main keyboard. Although

10541-448: The keytop for the O key also showed a left-arrow symbol (from ASCII-1963, which had this character instead of underscore ), a noncompliant use of code 15 (control-O, shift in) interpreted as "delete previous character" was also adopted by many early timesharing systems but eventually became neglected. When a Teletype 33 ASR equipped with the automatic paper tape reader received a control-S (XOFF, an abbreviation for transmit off), it caused

10668-699: The late 1980s. They were produced by the East German electronics manufacturer VEB Robotron . The following versions of MS-DOS were released to the public: Support for IBM's XT 10 MB hard disk drives, support up to 16 MB or 32 MB FAT12 -formatted hard disk drives depending on the formatting tool shipped by OEMs, user-installable device drivers, tree-structure filing system, Unix-like inheritable redirectable file handles, non-multitasking child processes an improved Terminate and Stay Resident (TSR) API, environment variables, device driver support, FOR and GOTO loops in batch files, ANSI.SYS . Microsoft DOS

10795-402: The limits of their contemporary hardware. Very soon an IBM-compatible architecture became the goal, and before long all 8086-family computers closely emulated IBM's hardware , and only a single version of MS-DOS for a fixed hardware platform was needed for the market. This version is the version of MS-DOS that is discussed here, as the dozens of other OEM versions of "MS-DOS" were only relevant to

10922-800: The local conventions and the NVT. The File Transfer Protocol adopted the Telnet protocol, including use of the Network Virtual Terminal, for use when transmitting commands and transferring data in the default ASCII mode. This adds complexity to implementations of those protocols, and to other network protocols, such as those used for E-mail and the World Wide Web, on systems not using the NVT's CR-LF line-ending convention. The PDP-6 monitor, and its PDP-10 successor TOPS-10, used control-Z (SUB) as an end-of-file indication for input from

11049-561: The operating system dropped support for 32-bit processors in favor of being solely offered in 64-bit versions only. This effectively ended any association of MS-DOS within Microsoft Windows after 36 years. MS-DOS 6.22 was the last standalone version produced by Microsoft for Intel 8088 , Intel 8086 , and Intel 80286 processors, which remains available for download via their MSDN , volume license, and OEM license partner websites, for customers with valid login credentials. MS-DOS

11176-600: The period when Digital Research was competing in the operating system market some computers, like the Amstrad PC1512 , were sold with floppy disks for two operating systems (only one of which could be used at a time), MS-DOS and CP/M-86 or a derivative of it. Digital Research produced DOS Plus , which was compatible with MS-DOS 2.11, supported CP/M-86 programs, had additional features including multi-tasking, and could read and write disks in CP/M and MS-DOS format. While OS/2

11303-519: The peripheral hardware of the IBM PC architecture. This design would have worked well for compatibility, if application programs had only used MS-DOS services to perform device I/O. Indeed, the same design philosophy is embodied in Windows NT (see Hardware Abstraction Layer ). However, in MS-DOS' early days, the greater speed attainable by programs through direct control of hardware was of particular importance, especially for games, which often pushed

11430-455: The platform without Microsoft and sold it as the alternative to DOS and Windows. As a response to Digital Research 's DR DOS 6.0 , which bundled SuperStor disk compression, Microsoft opened negotiations with Stac Electronics , vendor of the most popular DOS disk compression tool, Stacker. In the due diligence process, Stac engineers had shown Microsoft part of the Stacker source code. Stac

11557-452: The previous character in canonical input processing (where a very simple line editor is available); this could be set to BS or DEL, but not both, resulting in recurring situations of ambiguity where users had to decide depending on what terminal they were using ( shells that allow line editing, such as ksh , bash , and zsh , understand both). The assumption that no key sent a BS character allowed Ctrl+H to be used for other purposes, such as

11684-515: The previous section. Code 7F hex corresponds to the non-printable "delete" (DEL) control character and is therefore omitted from this chart; it is covered in the previous section's chart. Earlier versions of ASCII used the up arrow instead of the caret (5E hex ) and the left arrow instead of the underscore (5F hex ). ASCII was first used commercially during 1963 as a seven-bit teleprinter code for American Telephone & Telegraph 's TWX (TeletypeWriter eXchange) network. TWX originally used

11811-413: The printable characters, represent letters, digits, punctuation marks , and a few miscellaneous symbols. There are 95 printable characters in total. Code 20 hex , the "space" character, denotes the space between words, as produced by the space bar of a keyboard. Since the space character is considered an invisible graphic (rather than a control character) it is listed in the table below instead of in

11938-492: The program at the prompt ( CMD.EXE , 4NT.EXE , TCC.EXE ), can see the output. 64-bit Windows has neither the DOS emulation, nor the DOS commands EDIT, DEBUG and EDLIN that come with 32-bit Windows. The DOS version returns 5.00 or 5.50, depending on which API function is used to determine it. Utilities from MS-DOS 5.00 run in this emulation without modification. The very early beta programs of NT show MS-DOS 30.00, but programs running in MS-DOS 30.00 would assume that OS/2

12065-444: The proposed Bell code and ASCII were both ordered for more convenient sorting (i.e., alphabetization) of lists and added features for devices other than teleprinters. The use of ASCII format for Network Interchange was described in 1969. That document was formally elevated to an Internet Standard in 2015. Originally based on the (modern) English alphabet , ASCII encodes 128 specified characters into seven-bit integers as shown by

12192-522: The same reason, many special signs commonly used as separators were placed before digits. The committee decided it was important to support uppercase 64-character alphabets , and chose to pattern ASCII so it could be reduced easily to a usable 64-character set of graphic codes, as was done in the DEC SIXBIT code (1963). Lowercase letters were therefore not interleaved with uppercase . To keep options available for lowercase letters and other graphics,

12319-424: The same requests from customers that we have." – (Schulman et al. 1994). The pact between Microsoft and IBM to promote OS/2 began to fall apart in 1990 when Windows 3.0 became a marketplace success. Many of Microsoft's further contributions to OS/2 also went into creating a third GUI replacement for DOS, Windows NT . IBM, which had already been developing the next version of OS/2, carried on development of

12446-494: The second stick, positions 1–5, corresponding to the digits 1–5 in the adjacent stick. The parentheses could not correspond to 9 and 0 , however, because the place corresponding to 0 was taken by the space character. This was accommodated by removing _ (underscore) from 6 and shifting the remaining characters, which corresponded to many European typewriters that placed the parentheses with 8 and 9 . This discrepancy from typewriters led to bit-paired keyboards , notably

12573-470: The shared features of its "single-user OS" and "the multi-user, multi-tasking , UNIX -derived operating system", and promising easy porting between them. After the breakup of the Bell System , however, AT&T Computer Systems started selling UNIX System V . Believing that it could not compete with AT&T in the Unix market, Microsoft abandoned Xenix, and in 1987 transferred ownership of Xenix to

12700-538: The simple line characters \ | (in addition to common / ). The @ symbol was not used in continental Europe and the committee expected it would be replaced by an accented À in the French variation, so the @ was placed in position 40 hex , right before the letter A. The control codes felt essential for data transmission were the start of message (SOM), end of address (EOA), end of message (EOM), end of transmission (EOT), "who are you?" (WRU), "are you?" (RU),

12827-514: The slide show, and F6 moves to the next pane. ⇧ Shift + F9 exits the MS-DOS Shell if it is running. WordPerfect for DOS is an example of a program that made heavy use of function keys. In Internet Explorer 6 and Internet Explorer 7 , F12 opens Internet Explorer Developer Toolbar . F6 highlights the URL in the address bar. Function Keys are also heavily used in

12954-402: The special and numeric codes were arranged before the letters, and the letter A was placed in position 41 hex to match the draft of the corresponding British standard. The digits 0–9 are prefixed with 011, but the remaining 4 bits correspond to their respective values in binary, making conversion with binary-coded decimal straightforward (for example, 5 in encoded to 011 0101 , where 5

13081-425: The standard is unclear about the meaning of "delete". Probably the most influential single device affecting the interpretation of these characters was the Teletype Model 33 ASR, which was a printing terminal with an available paper tape reader/punch option. Paper tape was a very popular medium for long-term program storage until the 1980s, less costly and in some ways less fragile than magnetic tape. In particular,

13208-440: The structure or appearance of text within a document. Other schemes, such as markup languages , address page and document layout and formatting. The original ASCII standard used only short descriptive phrases for each control character. The ambiguity this caused was sometimes intentional, for example where a character would be used slightly differently on a terminal link than on a data stream , and sometimes accidental, for example

13335-515: The syntax of computer languages and text markup. ASCII hugely influenced the design of character sets used by modern computers, including Unicode which has over a million code points, but the first 128 of these are the same as ASCII. The Internet Assigned Numbers Authority (IANA) prefers the name US-ASCII for this character encoding. ASCII is one of the IEEE milestones . ASCII was developed in part from telegraph code . Its first commercial use

13462-401: The system. As MS-DOS 7.0 was a part of Windows 95, support for it also ended when Windows 95 extended support ended on December 31, 2001. As MS-DOS 7.10 and MS-DOS 8.0 were part of Windows 98 and Windows ME, respectively, support ended when Windows 98 and ME extended support ended on July 11, 2006, thus ending support and updates of MS-DOS from Microsoft. In contrast to the Windows 9x series,

13589-519: The systems they were designed for, and in any case were very similar in function and capability to some standard version for the IBM PC—often the same-numbered version, but not always, since some OEMs used their own proprietary version numbering schemes (e.g. labeling later releases of MS-DOS 1.x as 2.0 or vice versa)—with a few notable exceptions. Microsoft omitted multi-user support from MS-DOS because Microsoft's Unix -based operating system, Xenix ,

13716-441: The tape reader to stop; receiving control-Q (XON, transmit on) caused the tape reader to resume. This so-called flow control technique became adopted by several early computer operating systems as a "handshaking" signal warning a sender to stop transmission because of impending buffer overflow ; it persists to this day in many systems as a manual output control technique. On some systems, control-S retains its meaning, but control-Q

13843-600: The time could record eight bits in one position, it also allowed for a parity bit for error checking if desired. Eight-bit machines (with octets as the native data type) that did not use parity checking typically set the eighth bit to 0. The code itself was patterned so that most control codes were together and all graphic codes were together, for ease of identification. The first two so-called ASCII sticks (32 positions) were reserved for control characters. The "space" character had to come before graphics to make sorting easier, so it became position 20 hex ; for

13970-662: The two products diverged after twelve years, in 1993, with recognizable differences in compatibility, syntax and capabilities. Beginning in 1988 with DR-DOS , several competing products were released for the x86 platform. Initially, MS-DOS was targeted at Intel 8086 processors running on computer hardware using floppy disks to store and access not only the operating system, but application software and user data as well. Progressive version releases delivered support for other mass storage media in ever greater sizes and formats, along with added feature support for newer processors and rapidly evolving computer architectures. Ultimately, it

14097-447: The typebars that strike the ribbon remain stationary. The entire carriage had to be pushed (returned) to the right in order to position the paper for the next line. DEC operating systems ( OS/8 , RT-11 , RSX-11 , RSTS , TOPS-10 , etc.) used both characters to mark the end of a line so that the console device (originally Teletype machines) would work. By the time so-called "glass TTYs" (later called CRTs or "dumb terminals") came along,

14224-474: The use of Win32 console applications and internal commands with an NTCMDPROMPT directive. Win32 console applications use CMD.EXE as their command prompt shell. This confusion does not exist under OS/2 because there are separate DOS and OS/2 prompts, and running a DOS program under OS/2 will launch a separate DOS window to run the application. All versions of Windows for Itanium (no longer sold by Microsoft) and x86-64 architectures no longer include

14351-478: The version customized for their hardware, or face trying to get all of their proprietary hardware and software to work with the new system. In the business world, the 808x-based machines that MS-DOS was tied to faced competition from the Unix operating system; the latter ran on many different hardware architectures. Microsoft itself sold a version of Unix for the PC called Xenix . In the emerging world of home users,

14478-612: The version number and the VER internal command reports as "Windows Millennium" and "5.1", respectively, and not as "MS-DOS 8.0" (which was used as the base for Windows Me but never released as a stand-alone product), though the API still says Version 8.0. The creation of the MS-DOS startup disk was then carried over to later versions of Windows, with the majority of its contents remaining unchanged from its introduction in Windows XP. When creating

14605-414: The version of Mac OS X being used). As a result, default mappings are sometimes wrong (i.e., not matching the labels shown on the keyboard) when using a recent USB Apple keyboard on an older version of Mac OS X, which doesn't know about the new function key mapping of this keyboard (e.g., because Mission control and Launchpad didn't exist at that time, the corresponding labels shown on the keyboard can't match

14732-455: Was designed with a modular structure with internal device drivers (the DOS BIOS ), minimally for primary disk drives and the console, integrated with the kernel and loaded by the boot loader, and installable device drivers for other devices loaded and integrated at boot time. The OEM would use a development kit provided by Microsoft to build a version of MS-DOS with their basic I/O drivers and

14859-741: Was developed under the auspices of a committee of the American Standards Association (ASA), called the X3 committee, by its X3.2 (later X3L2) subcommittee, and later by that subcommittee's X3.2.4 working group (now INCITS ). The ASA later became the United States of America Standards Institute (USASI) and ultimately became the American National Standards Institute (ANSI). With the other special characters and control codes filled in, ASCII

14986-515: Was fully multi-user. The company planned, over time, to improve MS-DOS so it would be almost indistinguishable from single-user Xenix, or XEDOS , which would also run on the Motorola 68000 , Zilog Z8000 , and the LSI-11 ; they would be upwardly compatible with Xenix, which Byte in 1983 described as "the multi-user MS-DOS of the future". Microsoft advertised MS-DOS and Xenix together, listing

15113-657: Was in control. The OS/2 emulation is handled through OS2SS.EXE and OS2.EXE, and DOSCALLS.DLL. OS2.EXE is a version of the OS/2 shell (CMD.EXE), which passes commands down to the OS2SS.EXE, and input-output to the Windows NT shell. Windows 2000 was the last version of NT to support OS/2. The emulation is OS/2 1.30. POSIX is emulated through the POSIX shell, but no emulated shell; the commands are handled directly in CMD.EXE. The Command Prompt

15240-508: Was in the Teletype Model 33 and the Teletype Model 35 as a seven- bit teleprinter code promoted by Bell data services. Work on the ASCII standard began in May 1961, with the first meeting of the American Standards Association's (ASA) (now the American National Standards Institute or ANSI) X3.2 subcommittee. The first edition of the standard was published in 1963, underwent a major revision during 1967, and experienced its most recent update during 1986. Compared to earlier telegraph codes,

15367-695: Was published as ASA X3.4-1963, leaving 28 code positions without any assigned meaning, reserved for future standardization, and one unassigned control code. There was some debate at the time whether there should be more control characters rather than the lowercase alphabet. The indecision did not last long: during May 1963 the CCITT Working Party on the New Telegraph Alphabet proposed to assign lowercase characters to sticks 6 and 7, and International Organization for Standardization TC 97 SC 2 voted during October to incorporate

15494-1212: Was released through the OEM channel, until Digital Research released DR-DOS 5.0 as a retail upgrade. With PC DOS 5.00.1, the IBM–Microsoft agreement started to end, and IBM entered the retail DOS market with IBM DOS 5.00.1, 5.02, 6.00 and PC DOS 6.1, 6.3, 7, 2000 and 7.1. Localized versions of MS-DOS existed for different markets. While Western issues of MS-DOS evolved around the same set of tools and drivers just with localized message languages and differing sets of supported codepages and keyboard layouts, some language versions were considerably different from Western issues and were adapted to run on localized PC hardware with additional BIOS services not available in Western PCs, support multiple hardware codepages for displays and printers, support DBCS, alternative input methods and graphics output. Affected issues include Japanese ( DOS/V ), Korean, Arabic (ADOS 3.3/5.0), Hebrew (HDOS 3.3/5.0), Russian ( RDOS 4.01 / 5.0 ) as well as some other Eastern European versions of DOS. On microcomputers based on

15621-450: Was removed). ASCII was subsequently updated as USAS X3.4-1967, then USAS X3.4-1968, ANSI X3.4-1977, and finally, ANSI X3.4-1986. In the X3.15 standard, the X3 committee also addressed how ASCII should be transmitted ( least significant bit first) and recorded on perforated tape. They proposed a 9-track standard for magnetic tape and attempted to deal with some punched card formats. The X3.2 subcommittee designed ASCII based on

15748-507: Was seen as the legitimate heir to the "kludgy" DOS platform. MS-DOS had grown in spurts, with many significant features being taken or duplicated from Microsoft's other products and operating systems. MS-DOS also grew by incorporating, by direct licensing or feature duplicating, the functionality of tools and utilities developed by independent companies, such as Norton Utilities , PC Tools ( Microsoft Anti-Virus ), QEMM expanded memory manager, Stacker disk compression , and others. During

15875-517: Was the key product in Microsoft's development from a programming language company to a diverse software development firm, providing the company with essential revenue and marketing resources. It was also the underlying basic operating system on which early versions of Windows ran as a GUI. MS-DOS went through eight versions, until development ceased in 2000; version 6.22 from 1994 was the final standalone version, with versions 7 and 8 serving mostly in

16002-506: Was under protracted development, Digital Research released the MS-DOS compatible DR-DOS 5.0, which included features only available as third-party add-ons for MS-DOS. Unwilling to lose any portion of the market, Microsoft responded by announcing the "pending" release of MS-DOS 5.0 in May 1990. This effectively killed most DR DOS sales until the actual release of MS-DOS 5.0 in June 1991. Digital Research brought out DR DOS 6.0, which sold well until

16129-592: Was unwilling to meet Microsoft's terms for licensing Stacker and withdrew from the negotiations. Microsoft chose to license Vertisoft's DoubleDisk, using it as the core for its DoubleSpace disk compression. MS-DOS 6.0 and 6.20 were released in 1993, both including the Microsoft DoubleSpace disk compression utility program. Stac successfully sued Microsoft for patent infringement regarding the compression algorithm used in DoubleSpace. This resulted in

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