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{{short description|American computer character encoding}}{{Distinguish|text=MS Windows-1252 or other types of extended ASCII}}{{About|the character encoding}}{{Use mdy dates|date=June 2013}}{{Use American English|date=December 2018}}

< .> 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 common characters were not included, notably ½¼¢, while ^`~ were included as diacritics for international use, and <> for mathematical use, together with 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 40hex, right before the letter A.{{rp|243}}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), a reserved device control (DC0), synchronous idle (SYNC), and acknowledge (ACK). These were positioned to maximize the Hamming distance between their bit patterns.{{rp|243–245}}

{{anchor|Order}}Character order

ASCII-code order is also called ASCIIbetical order.JOURNAL,weblink ASCIIbetical definition, PC Magazine, 2008-04-14, Collation of data is sometimes done in this order rather than "standard" alphabetical order (collating sequence). The main deviations in ASCII order are:
  • All uppercase come before lowercase letters; for example, "Z" precedes "a"
  • Digits and many punctuation marks come before letters
An intermediate order converts uppercase letters to lowercase before comparing ASCII values.

Character groups

{{anchor|ASCII control characters}}Control characters

ASCII reserves the first 32 codes (numbers 0–31 decimal) for control characters: codes originally intended not to represent printable information, but rather to control devices (such as printers) that make use of ASCII, or to provide meta-information about data streams such as those stored on magnetic tape.For example, character 10 represents the "line feed" function (which causes a printer to advance its paper), and character 8 represents "backspace". {{IETF RFC|2822}} refers to control characters that do not include carriage return, line feed or white space as non-whitespace control characters.{{citation |title=Internet Message Format |author-first=P. |author-last=Resnick |date=April 2001 |rfc=2822 |url= |access-date=2016-06-13 |dead-url=no |archive-url= |archive-date=2016-06-13}} (NB. NO-WS-CTL.) Except for the control characters that prescribe elementary line-oriented formatting, ASCII does not define any mechanism for describing 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 with the meaning of "delete".Probably the most influential single device on 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, 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 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 the tape reader to stop; receiving Control-Q (XON, "transmit on") caused the tape reader to resume. This technique became adopted by several early computer operating systems as a "handshaking" signal warning a sender to stop transmission because of impending 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 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.WEB, Understanding ASCII Codes, McConnell, Robert, Haynes, James, Warren, Richard,weblink 2014-05-11, The Teletype could not move the head backwards, so it did not put a key on the keyboard to send a BS (backspace). Instead there was a key marked {{keypress|RUB OUT}} that sent code 127 (DEL). The purpose of this key was to erase mistakes in a hand-typed 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.MAILING LIST,weblink Re: editor and word processor history (was: Re: RTF for emacs), Barry Margolin, help-gnu-emacs, May 29, 2014, Teletypes were commonly used for the less-expensive computers from Digital Equipment Corporation, so these systems had to use the available key and thus the DEL code to erase the previous character.WEB,weblink PDP-6 Multiprogramming System Manual, 43, Digital Equipment Corporation (DEC), 1965, WEB,weblink PDP-10 Reference Handbook, Book 3, Communicating with the Monitor, p. 5-5, Digital Equipment Corporation (DEC), 1969, Because of this, DEC video terminals (by default) sent the DEL code for the key marked "Backspace" while the key marked "Delete" sent an escape sequence, while many other terminals sent BS for the Backspace key. The Unix terminal driver could only use one code to erase the previous character, this could be set to BS or DEL, but not both, resulting in a long period of annoyance where users had to correct it 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 caused Control+H to be used for other purposes, such as the "help" prefix command in GNU Emacs.WEB,weblink Help - GNU Emacs Manual, Many more of the control codes have been given meanings quite different from their original ones. The "escape" character (ESC, code 27), for example, was intended originally to allow sending other control characters as literals instead of invoking their meaning. This is the same meaning of "escape" encountered in URL encodings, C language strings, and other systems where certain characters have a reserved meaning. Over time this meaning has been co-opted and has eventually been changed. In modern use, an ESC sent to the terminal usually indicates the start of a command sequence usually in the form of a so-called "ANSI escape code" (or, more properly, a "Control Sequence Introducer") from ECMA-48 (1972) and its successors, beginning with ESC followed by a "[" (left-bracket) character. An ESC sent from the terminal is most often used as an out-of-band character used to terminate an operation, as in the TECO and vitext 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 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 moved while the position where the typebars struck the ribbon remained stationary. The entire carriage had to be pushed (returned) to the right in order to position the left margin of 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 terminals) came along, the convention was so well established that backward compatibility necessitated continuing the convention. When Gary Kildall created CP/M he was inspired by some command line interface conventions used in DEC's RT-11. Until the introduction of PC DOS in 1981, IBM had no hand in this because their 1970s operating systems used EBCDIC instead of ASCII and they were oriented toward punch-card input and line printer output on which 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,WEB,weblink Is DOS a Rip-Off of CP/M?, Tim Paterson, August 8, 2007, DosMan Drivel, Tim Paterson, and Windows inherited it from MS-DOS.Unfortunately, requiring two characters to mark the end of a line introduces unnecessary complexity and questions as to how to interpret each character when encountered alone. To simplify matters plain text data streams, including files, on MulticsCONFERENCE,weblink Technical and human engineering problems in connecting terminals to a time-sharing system, Ossanna, J. F., Joe Ossanna, Saltzer, J. H., Jerry Saltzer, November 17–19, 1970, AFIPS Press, Proceedings of the November 17–19, 1970, Fall Joint Computer Conference (FJCC), 355–362, p. 357, Using a "new-line" function (combined carriage-return and line-feed) is simpler for both man and machine than requiring both functions for starting a new line; the American National Standard X3.4-1968 permits the line-feed code to carry the new-line meaning., used line feed (LF) alone as a line terminator. Unix and Unix-like systems, and Amiga systems, adopted this convention from Multics. The original Macintosh OS, Apple DOS, and ProDOS, on the other hand, used carriage return (CR) alone as a line terminator; however, since Apple replaced these operating systems with the Unix-based macOS 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 a character count followed by the characters of the line and that used EBCDIC rather than ASCII. 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 the local conventions and the NVT.{{citation |title=TELNET Protocol |rfc=158 |pages=4–5 |author-first=T. |author-last=O'Sullivan |date=1971-05-19 |publisher=Internet Engineering Task Force (IETF) |url= |access-date=2013-01-28 |dead-url=no |archive-url= |archive-date=2016-06-13}} 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.{{citation |title=File Transfer Protocol |rfc=542 |author-first=Nancy J. |author-last=Neigus |date=1973-08-12 |publisher=Internet Engineering Task Force (IETF) |url= |access-date=2013-01-28 |dead-url=no |archive-url= |archive-date=2016-06-13}}{{citation |title=File Transfer Protocol |rfc=765 |author-first=Jon |author-last=Postel |author-link=Jon Postel |date=June 1980 |publisher=Internet Engineering Task Force (IETF) |url= |access-date=2013-01-28 |dead-url=no |archive-url= |archive-date=2016-06-13}} 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.WEB,weblink EOL translation plan for Mercurial, Mercurial, 2017-06-24, WEB, Bare LFs in SMTP,weblink Daniel J., Bernstein, Daniel J. Bernstein, 2013-01-28, The PDP-6 monitor, and its PDP-10 successor TOPS-10, used Control-Z (SUB) as an end-of-file indication for input from 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.BOOK,weblink CP/M 1.4 Interface Guide, 1978, 10, Digital Research, 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 code (ETX), also known as Control-C, was inappropriate for a variety of reasons, while using Z as the control code to end a file is analogous to it ending the alphabet and serves as a very convenient mnemonic aid. A historically common and still prevalent convention uses the ETX code convention to interrupt and halt a program via an input data stream, usually from a keyboard.In C library and 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".{{anchor|ASCII control code chart}}{| class="wikitable" style="text-align: center"! rowspan="2"|Binary !! rowspan="2"|Oct !! rowspan="2"|Dec !! rowspan="2"|Hex !! colspan="3"|Abbreviation !! rowspan="2"|{{Efn|The Unicode characters from the area U+2400 to U+2421 reserved for representing control characters when it is necessary to print or display them rather than have them perform their intended function. Some browsers may not display these properly.}} !! rowspan="2"|{{Efn|Caret notation is often used to represent control characters on a terminal. On most text terminals, holding down the {{key press|Ctrl}} key while typing the second character will type the control character. Sometimes the shift key is not needed, for instance ^@ may be typable with just Ctrl and 2.}} !! rowspan="2"|{{Efn|Character escape sequences in C programming language and many other languages influenced by it, such as Java and Perl (though not all implementations necessarily support all escape sequences).}} !! rowspan="2"|Name (1967)! 1963 !! 1965 !! 1967
| name ASCII| alias = ASCII| mime = us-ascii| image = ASCII-infobox.svg| caption = ASCII (1967 or later)

English language>English| extensions = * Unicode
    ASCII ({{IPAc-en|audio=En-us-ASCII.ogg|ˈ|æ|s|k|iː}} {{respell|ASS|kee}}),BOOK,weblink Coded Character Sets, History and Development, The Systems Programming Series, Mackenzie, Charles E., 1980, 1, Addison-Wesley Publishing Company, Inc., 978-0-201-14460-4, 77-90165, 6, 66, 211, 215, 217, 220, 223, 228, 236–238, 243–245, 247–253, 423, 425–428, 435–439, 2019-05-02,weblink May 26, 2016, no, mdy-all, {{rp|6}} abbreviated from 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. Most modern character-encoding schemes are based on ASCII, although they support many additional characters.ASCII is the traditional name for the encoding system; the Internet Assigned Numbers Authority (IANA) prefers the updated name US-ASCII, which clarifies that this system was developed in the US and based on the typographical symbols predominantly in use there.Internet Assigned Numbers Authority (IANA) (May 14, 2007). "Character Sets". Accessed 2008-04-14.ASCII is one of the IEEE milestones.(File:USASCII code chart.png|thumb|361px|ASCII chart from an earlier-than 1972 printer manual (b1 is the least significant bit.))


    ASCII was developed from telegraph code. Its first commercial use was as a seven-bit teleprinter code promoted by Bell data services. Work on the ASCII standard began on October 6, 1960, 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,NEWS, Mary, Brandel, July 6, 1999,weblink 1963: The Debut of ASCII, CNN, 2008-04-14, WEB, American Standard Code for Information Interchange, ASA X3.4-1963, American Standards Association (ASA), 1963-06-17,weblink 2018-09-28, no,weblink" title="">weblink September 28, 2018, underwent a major revision during 1967,JOURNAL, USA Standard Code for Information Interchange, USAS X3.4-1967, United States of America Standards Institute (USASI), July 7, 1967, WEB, An annotated history of some character codes or ASCII: American Standard Code for Information Infiltration, Thomas Daniel, Jennings, Thomas Daniel Jennings, World Power Systems (WPS), 2016-04-20, 1999,weblink 2018-09-28, no,weblink" title="">weblink September 28, 2018, and experienced its most recent update during 1986.JOURNAL, American National Standard for Information Systems — Coded Character Sets — 7-Bit American National Standard Code for Information Interchange (7-Bit ASCII), ANSI X3.4-1986, American National Standards Institute (ANSI), March 26, 1986, Compared to earlier telegraph codes, 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.Originally based on the English alphabet, ASCII encodes 128 specified characters into seven-bit integers as shown by the ASCII chart above.{{citation |title=Internet Security Glossary, Version 2 |date=August 2007 |author-first=R. |author-last=Shirley |rfc=4949 |url= |access-date=2016-06-13 |dead-url=no |archive-url= |archive-date=2016-06-13}} 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 machines; most of these are now obsolete,BOOK, Maini, Anil Kumar, Digital Electronics: Principles, Devices and Applications,weblink 2007, John Wiley and Sons, 978-0-470-03214-5, 28, In addition, it defines codes for 33 nonprinting, mostly obsolete control characters that affect how the text is processed., although a few are still commonly used, such as 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.


    File:ASCII1963-infobox-paths.svg|thumb|right|ASCII (1963). Control pictures of equivalent controls are shown where they exist, or a grey dot otherwise.]]The American Standard Code for Information Interchange (ASCII) 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 became the United States of America Standards Institute (USASI){{rp|211}} and ultimately the American National Standards Institute (ANSI).With the other special characters and control codes filled in, ASCII was published as ASA X3.4-1963,JOURNAL, Binary Computer Codes and ASCII, Ed, Bukstein, Electronics World, July 1964, 72, 1, 28–29,weblink 2016-05-22, leaving 28 code positions without any assigned meaning, reserved for future standardization, and one unassigned control code.{{rp|66, 245}} There was some debate at the time whether there should be more control characters rather than the lowercase alphabet.{{rp|435}} 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{{Efn|name="NB_Stick"|{{anchor|Stick}}The 128 characters of the 7-bit ASCII character set are divided into eight 16-character groups called sticks 0–7, associated with the three most-significant bits. Depending on the horizontal or vertical representation of the character map, sticks correspond with either table rows or columns.}} 6 and 7,Brief Report: Meeting of CCITT Working Party on the New Telegraph Alphabet, May 13–15, 1963. and International Organization for Standardization TC 97 SC 2 voted during October to incorporate the change into its draft standard.Report of ISO/TC/97/SC 2 – Meeting of October 29–31, 1963. The X3.2.4 task group voted its approval for the change to ASCII at its May 1963 meeting.Report on Task Group X3.2.4, June 11, 1963, Pentagon Building, Washington, DC. Locating the lowercase letters in sticks{{Efn|name="NB_Stick"}} 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),Report of Meeting No. 8, Task Group X3.2.4, December 17 and 18, 1963 renaming some control characters (SOM became start of header (SOH)) and moving or removing others (RU was removed).{{rp|247–248}} ASCII was subsequently updated as USAS X3.4-1967,WEB, US and International standards: ASCII,weblink Dik T., Winter, 2010, 2003, yes,weblink" title="">weblink 2010-01-16, then USAS X3.4-1968, ANSI X3.4-1977, and finally, ANSI X3.4-1986.WEB, 7-bit character sets: Revisions of ASCII, Tuomas, Salste, Aivosto Oy, January 2016, {{URN, nbn, fi-fe201201011004, |url= |access-date=2016-06-13 |dead-url=no |archive-url= |archive-date=2016-06-13}}Revisions of the ASCII standard:
    • ASA X3.4-1963
    • ASA X3.4-1965 (approved, but not published, nevertheless used by IBM 2260 & 2265 Display Stations and IBM 2848 Display Control){{rp|423, 425–428, 435–439}}JOURNAL, Information, September 1966, 215, 3, special edition, Scientific American, e24931041,
    • USAS X3.4-1967
    • USAS X3.4-1968
    • ANSI X3.4-1977
    • ANSI X3.4-1986
    • ANSI X3.4-1986 (R1992)
    • ANSI X3.4-1986 (R1997)
    • ANSI INCITS 4-1986 (R2002)BOOK, Unicode Explained – Internationalize Documents, Programs, and Web Sites, Jukka K., Korpela, 2nd release of 1st, 2014-03-14, 2006-06-07, O'Reilly Media, Inc., 978-0-596-10121-3, 118,
    • ANSI INCITS 4-1986 (R2007){{citation |title=ANSI INCITS 4-1986 (R2007): American National Standard for Information Systems – Coded Character Sets – 7-Bit American National Standard Code for Information Interchange (7-Bit ASCII) |date=2007 |orig-year=1986 |id= |url= |access-date=2016-06-12 |dead-url=no |archive-url= |archive-date=2014-02-07}}
    • ANSI INCITS 4-1986 (R2012)
    In the X3.15 standard, the X3 committee also addressed how ASCII should be transmitted (least significant bit first),{{rp|249–253}}{{citation |title=Bit Sequencing of the American National Standard Code for Information Interchange in Serial-by-Bit Data Transmission |id=X3.15-1966 |date=1966 |publisher=American National Standards Institute (ANSI)}} and how it should be recorded on perforated tape. They proposed a 9-track standard for magnetic tape, and attempted to deal with some punched card formats.

    Design considerations

    Bit width

    The X3.2 subcommittee designed ASCII based on 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 the Comité Consultatif International Téléphonique et Télégraphique (CCITT) International Telegraph Alphabet No. 2 (ITA2) standard of 1924,WEB, BruXy: Radio Teletype communication, 2005-10-10, 2016-05-09,weblink The transmitted code use International Telegraph Alphabet No. 2 (ITA-2) which was introduced by CCITT in 1924., WEB, Smith, Gil, Teletype Communication Codes,, 2001,weblink 2008-07-11, FIELDATA (1956{{citation needed|date=June 2016|reason=My sources state 1957 rather than 1956, but Wikipedia states 1956 in various places. This needs to be sorted out with better sources.}}), and early EBCDIC (1963), more than 64 codes were required for ASCII.ITA2 were in turn based on the 5-bit telegraph code Émile Baudot invented in 1870 and patented in 1874.The committee debated the possibility of 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 a seven-bit code.{{rp|215, 236 § 4}}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 the time could record eight bits in one position, it also allowed for a parity bit for error checking if desired.{{rp|217, 236 § 5}} Eight-bit machines (with octets as the native data type) that did not use parity checking typically set the eighth bit to 0.BOOK, Stanley A., Sawyer, Steven George, Krantz, A TeX Primer for Scientists,weblink 1995, CRC Press, LLC, 978-0-8493-7159-2, 13,, In some printers, the high bit was used to enable Italics printing{{Citation needed|date=May 2019}}.

    Internal organization

    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{{Efn|name="NB_Stick"}} (32 positions) were reserved for control characters.{{rp|220, 236 § 8,9)}} The "space" character had to come before graphics to make sorting easier, so it became position 20hex;{{rp|237 § 10}} for 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,{{rp|228, 237 § 14}} 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, the special and numeric codes were arranged before the letters, and the letter A was placed in position 41hex to match the draft of the corresponding British standard.{{rp|238 § 18}} 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.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.WEB, Computer Keyboards,weblink John J. G., Savard, 2014-08-24, Mechanical typewriters followed the standard set by the Remington No. 2 (1878), the first typewriter with a shift key, and the shifted values of 23456789- were "#$%_&'(){{snd}} early typewriters omitted 0 and 1, using O (capital letter o) and l (lowercase letter L) instead, but 1! and 0) pairs became standard once 0 and 1 became common. Thus, in ASCII !"#$% were placed in the second stick,{{Efn|name="NB_Stick"}} positions 1–5, corresponding to the digits 1–5 in the adjacent stick.{{Efn|name="NB_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 the Teletype Model 33, which used the left-shifted layout corresponding to ASCII, not to traditional mechanical typewriters. Electric typewriters, notably the IBM Selectric (1961), used a somewhat different layout that has become standard on computers{{snd}} following the IBM PC (1981), especially Model M (1984){{snd}} and thus shift values for symbols on modern keyboards do not correspond as closely to the ASCII table as earlier keyboards did. The /? pair also dates to the No. 2, and the ,
    000 style="background:#CFF;" 00NUL style="font-size:large;" ^@ > > Null
    001 style="background:#CFF;" 01SOH style="font-size:large;" ^A > Start of Heading
    002 style="background:#CFF;" 02STX style="font-size:large;" ^B > Start of Text
    003 style="background:#CFF;" 03ETX style="font-size:large;" ^C > End of Text
    004 style="background:#CFF;" 04EOT style="font-size:large;" ^D > End of Transmission
    005 style="background:#CFF;" 05ENQ style="font-size:large;" ^E > Enquiry
    006 style="background:#CFF;" 06ACK style="font-size:large;" ^F > Acknowledgement
    007 style="background:#CFF;" 07BEL style="font-size:large;" ^G >a > Bell
    010 style="background:#CFF;" 08BS style="font-size:large;" ^H >Backspace>b style="text-align:left;" Backspace{{Efn>The Backspace character can also be entered by pressing the {{key pressname="bsp del mismatch"}}
    011 style="background:#CFF;" 09HT style="font-size:large;" ^I >t > Horizontal Tab{{EfnTab character can also be entered by pressing the {{key press>Tab}} key on most systems.}}
    012 style="background:#CFF;" 0ALF style="font-size:large;" ^J >n > Line Feed
    013 style="background:#CFF;" 0BVT style="font-size:large;" ^K >v > Vertical Tab
    014 style="background:#CFF;" 0CFF style="font-size:large;" ^L >f > Form Feed
    015 style="background:#CFF;" 0DCR style="font-size:large;" ^M >r > Carriage Return{{EfnCarriage Return character can also be entered by pressing the {{key press>Enter}} or {{key press|Return}} key on most systems.}}
    016 style="background:#CFF;" 0ESO style="font-size:large;" ^N > Shift Out
    017 style="background:#CFF;" 0FSI style="font-size:large;" ^O > Shift In
    020 style="background:#CFF;" 10DLE style="font-size:large;" ^P > Data Link Escape
    021 style="background:#CFF;" 11DC1 style="font-size:large;" ^Q > Device Control 1 (often XON)
    022 style="background:#CFF;" 12DC2 style="font-size:large;" ^R > Device Control 2
    023 style="background:#CFF;" 13DC3 style="font-size:large;" ^S > Device Control 3 (often XOFF)
    024 style="background:#CFF;" 14DC4 style="font-size:large;" ^T > Device Control 4
    025 style="background:#CFF;" 15NAK style="font-size:large;" ^U > Negative Acknowledgement
    026 style="background:#CFF;" 16SYN style="font-size:large;" ^V > Synchronous Idle
    027 style="background:#CFF;" 17ETB style="font-size:large;" ^W > End of Transmission Block
    030 style="background:#CFF;" 18CAN style="font-size:large;" ^X > Cancel
    031 style="background:#CFF;" 19EM style="font-size:large;" ^Y > End of Medium
    032 style="background:#CFF;" 1A ␚ ^Z style="text-align:left;" Substitute character>Substitute
    033 style="background:#CFF;" 1BESC style="font-size:large;" e{{Efn>The e escape sequence is not part of ISO C and many other language specifications. However, it is understood by several compilers, including GCC (software).}} > Escape character{{Efn>The Escape character can also be entered by pressing the {{key press|Esc}} key on some systems.}}
    034 style="background:#CFF;" 1CFS style="font-size:large;" ^ > File Separator
    035 style="background:#CFF;" 1DGS style="font-size:large;" Group Separator
    036 style="background:#CFF;" 1ERS style="font-size:large;" ^^ means {{key press^}} (pressing the "Ctrl" and caret keys).}} style="text-align:left;" | Record Separator
    037 style="background:#CFF;" 1FUS style="font-size:large;" Unit Separator
    177 style="background:#CFF;" 7FDEL style="font-size:large;" ^? > Delete character{{Efn>The Delete character can sometimes be entered by pressing the {{key pressname="bsp del mismatch"Backspace is due to early terminals designed assuming the main use of the keyboard would be to manually punch paper tape while not connected to a computer. To delete the previous character, one had to back up the paper tape punch, which for mechanical and simplicity reasons was a button on the punch itself and not the keyboard, then type the rubout character. They therefore placed a key producing rubout at the location used on typewriters for backspace. When systems used these terminals and provided command-line editing, they had to use the "rubout" code to perform a backspace, and often did not interpret the backspace character (they might echo "^H" for backspace). Other terminals not designed for paper tape made the key at this location produce Backspace, and systems designed for these used that character to back up. Since the delete code often produced a backspace effect, this also forced terminal manufacturers to make any {{key press>Delete}} key produce something other than the Delete character.}}
    Other representations might be used by specialist equipment, for example ISO 2047 graphics or hexadecimal numbers.

    {{anchor|ASCII-printable-characters}}Printable characters

    Codes 20hex to 7Ehex, known as the printable characters, represent letters, digits, punctuation marks, and a few miscellaneous symbols. There are 95 printable characters in total.{{efn|Printed out, the characters are: {{Pre2|scroll| !"#$%&'()*+,-./0123456789:;?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[]^_`abcdefghijklmnopqrstuvwxyz{|}~}}}}Code 20hex, 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){{rp|223}}{{citation |title=ASCII format for Network Interchange |author-first=Vinton Gray |author-last=Cerf |author-link=Vinton Gray Cerf |publisher=Network Working Group |date=1969-10-16 |rfc=20 |url= |access-date=2016-06-13 |dead-url=no |archive-url= |archive-date=2016-06-13}} (NB. Almost identical wording to USAS X3.4-1968 except for the intro.) it is listed in the table below instead of in the previous section.Code 7Fhex 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 (5Ehex) and the left arrow instead of the underscore (5Fhex).WEB, First-Hand: Chad is Our Most Important Product: An Engineer's Memory of Teletype Corporation, Jim, Engineering and Technology History Wiki (ETHW), 2015-01-13, Haynes,weblink's_Memory_of_Teletype_Corporation, 2016-10-31, no,weblink" title="">weblink October 31, 2016, There was the change from 1961 ASCII to 1968 ASCII. Some computer languages used characters in 1961 ASCII such as up arrow and left arrow. These characters disappeared from 1968 ASCII. We worked with Fred Mocking, who by now was in Sales at Teletype Corporation, Teletype, on a type cylinder that would compromise the changing characters so that the meanings of 1961 ASCII were not totally lost. The underscore character was made rather wedge-shaped so it could also serve as a left arrow., {| class="wikitable" style="text-align: center;"! rowspan="2"|Binary !! rowspan="2"|Oct !! rowspan="2"|Dec !! rowspan="2"|Hex !! colspan="3"|Glyph! 1963 !! 1965 !! 1967 040 style="background:#cff;" 20 colspan=3space (punctuation)>space 041 style="background:#cff;" 21 colspan=3Exclamation mark>! 042 style="background:#cff;" 22 colspan=3Quotation mark>" 043 style="background:#cff;" 23 colspan=3Number sign># 044 style="background:#cff;" 24 colspan=3Dollar sign>$ 045 style="background:#cff;" 25 colspan=3Percent sign>% 046 style="background:#cff;" 26 colspan=3Ampersand>& 047 style="background:#cff;" 27 colspan=3Apostrophe>' 050 style="background:#cff;" 28 colspan=3Left parenthesis>( 051 style="background:#cff;" 29 colspan=3Right parenthesis>) 052 style="background:#cff;" 2A colspan=3Asterisk>* 053 style="background:#cff;" 2B colspan=3Plus sign>+ 054 style="background:#cff;" 2C colspan=3Comma>, 055 style="background:#cff;" 2D colspan=3Hyphen-minus>- 056 style="background:#cff;" 2E colspan=3Full stop>. 057 style="background:#cff;" 2F colspan=3Slash (punctuation)>/ 060 style="background:#cff;" 30 colspan=30 (number)>0 061 style="background:#cff;" 31 colspan=31 (number)>1 062 style="background:#cff;" 32 colspan=32 (number)>2 063 style="background:#cff;" 33 colspan=33 (number)>3 064 style="background:#cff;" 34 colspan=34 (number)>4 065 style="background:#cff;" 35 colspan=35 (number)>5 066 style="background:#cff;" 36 colspan=36 (number)>6 067 style="background:#cff;" 37 colspan=37 (number)>7 070 style="background:#cff;" 38 colspan=38 (number)>8 071 style="background:#cff;" 39 colspan=39 (number)>9 072 style="background:#cff;" 3A colspan=3:) 073 style="background:#cff;" 3B colspan=3Semicolon>; 074 style="background:#cff;" 3C colspan=3Less-than sign> 077 style="background:#cff;" 3F colspan=3Question mark>? 100 style="background:#cff;" 40 At sign >Grave accent>` @ 101 style="background:#cff;" 41 colspan=3|A 102 style="background:#cff;" 42 colspan=3|B 103 style="background:#cff;" 43 colspan=3|C 104 style="background:#cff;" 44 colspan=3|D 105 style="background:#cff;" 45 colspan=3|E 106 style="background:#cff;" 46 colspan=3|F 107 style="background:#cff;" 47 colspan=3|G 110 style="background:#cff;" 48 colspan=3|H 111 style="background:#cff;" 49 colspan=3|I 112 style="background:#cff;" 4A colspan=3|J 113 style="background:#cff;" 4B colspan=3|K 114 style="background:#cff;" 4C colspan=3|L 115 style="background:#cff;" 4D colspan=3|M 116 style="background:#cff;" 4E colspan=3|N 117 style="background:#cff;" 4F colspan=3|O 120 style="background:#cff;" 50 colspan=3|P 121 style="background:#cff;" 51 colspan=3|Q 122 style="background:#cff;" 52 colspan=3|R 123 style="background:#cff;" 53 colspan=3|S 124 style="background:#cff;" 54 colspan=3|T 125 style="background:#cff;" 55 colspan=3|U 126 style="background:#cff;" 56 colspan=3|V 127 style="background:#cff;" 57 colspan=3|W 130 style="background:#cff;" 58 colspan=3|X 131 style="background:#cff;" 59 colspan=3|Y 132 style="background:#cff;" 5A colspan=3|Z 133 style="background:#cff;" 5B colspan=3Left square bracket>[ 134 style="background:#cff;" 5C Backslash >Tilde>~ 135 style="background:#cff;" 5D colspan=3Right square bracket>] 136 style="background:#cff;" 5E Up arrow (symbol) >^ 137 style="background:#cff;" 5F Left arrow (symbol) >_ 140 style="background:#cff;" 60 At sign >Grave accent>` 141 style="background:#cff;" 61 colspan=2|a 142 style="background:#cff;" 62 colspan=2|b 143 style="background:#cff;" 63 colspan=2|c 144 style="background:#cff;" 64 colspan=2|d 145 style="background:#cff;" 65 colspan=2|e 146 style="background:#cff;" 66 colspan=2|f 147 style="background:#cff;" 67 colspan=2|g 150 style="background:#cff;" 68 colspan=2|h 151 style="background:#cff;" 69 colspan=2|i 152 style="background:#cff;" 6A colspan=2|j 153 style="background:#cff;" 6B colspan=2|k 154 style="background:#cff;" 6C colspan=2|l 155 style="background:#cff;" 6D colspan=2|m 156 style="background:#cff;" 6E colspan=2|n 157 style="background:#cff;" 6F colspan=2|o 160 style="background:#cff;" 70 colspan=2|p 161 style="background:#cff;" 71 colspan=2|q 162 style="background:#cff;" 72 colspan=2|r 163 style="background:#cff;" 73 colspan=2|s 164 style="background:#cff;" 74 colspan=2|t 165 style="background:#cff;" 75 colspan=2|u 166 style="background:#cff;" 76 colspan=2|v 167 style="background:#cff;" 77 colspan=2|w 170 style="background:#cff;" 78 colspan=2|x 171 style="background:#cff;" 79 colspan=2|y 172 style="background:#cff;" 7A colspan=2|z 173 style="background:#cff;" 7B colspan=2Left curly bracket>{ 174 style="background:#cff;" 7C Acknowledge character >Not sign>¬ Vertical bar 175 style="background:#cff;" 7D colspan=2Right curly bracket>} 176 style="background:#cff;" 7E Escape character >Vertical bar> >Tilde>~

    {{anchor|Code chart|ASCII printable code chart|ASCII printable characters}}Character set

    Points which represented a different character in previous versions (the 1963 version and/or the 1965 draft) are shown boxed. Points assigned since the 1963 version but otherwise unchanged are shown lightly shaded relative to their legend colours.{| {{chset-tableformat}}{{chset-table-header|ASCII (1977/1986)}}!{{chset-left2|0_0}}{{chset-ctrlNull character>0}}{{chset-ctrlStart of heading>1}}{{chset-ctrlStart of text>2}}{{chset-ctrlEnd of text>3}}{{chset-ctrlEnd of transmission character>4}}{{chset-ctrlEnquiry character>5}}{{chset-ctrlAcknowledge character>6}}{{chset-ctrlBell character>7}}{{chset-ctrlBackspace>8}}{{chset-ctrlHorizontal tabulation>9}}{{chset-ctrlLine feed>10}}{{chset-ctrlVertical tabulation>11}}{{chset-ctrlForm feed>12}}{{chset-ctrlCarriage return>13}}{{chset-ctrlShift out>14}}{{chset-ctrlShift in>15}}!{{chset-left2|1_16}}{{chset-ctrlData link escape>16}}{{chset-ctrlDevice Control 1>17}}{{chset-ctrlDevice Control 2>18}}{{chset-ctrlDevice Control 3>19}}{{chset-ctrlDevice Control 4>20}}{{chset-ctrlNegative acknowledge character>21}}{{chset-ctrlSynchronous idle>22}}{{chset-ctrlEnd of transmission block>23}}{{chset-ctrlCancel character>24}}{{chset-ctrlEnd of medium>25}}{{chset-ctrlSubstitute character>26}}{{chset-ctrlEscape character>27}}{{chset-ctrlFile separator>28}}{{chset-ctrlGroup separator>29}}{{chset-ctrlRecord separator>30}}{{chset-ctrlUnit separator>31}}!{{chset-left2|2_32}}{{chset-ctrlSpace character>32}}{{chset-cellExclamation mark>33}}{{chset-cellQuotation mark>34}}{{chset-cellNumber sign>35}}{{chset-cellDollar sign>36}}{{chset-cellPercent sign>37}}{{chset-cellAmpersand>38}}{{chset-cellApostrophe>39}}{{chset-cellLeft parenthesis>40}}{{chset-cellRight parenthesis>41}}{{chset-cellAsterisk>42}}{{chset-cellPlus sign>43}}{{chset-cellComma (punctuation)>44}}{{chset-cellHyphen-minus>45}}{{chset-cellFull stop>46}}{{chset-cellSlash (punctuation)>47}}!{{chset-left2|3_48}}{{chset-cell0|48}}{{chset-cell1|49}}{{chset-cell2|50}}{{chset-cell3|51}}{{chset-cell4|52}}{{chset-cell5|53}}{{chset-cell6|54}}{{chset-cell7|55}}{{chset-cell8|56}}{{chset-cell9|57}}{{chset-cell(Colon (punctuation)58}}{{chset-cellSemicolon>59}}{{chset-cellLess-than sign>60}}{{chset-cellEqual sign>61}}{{chset-cellGreater-than sign>62}}{{chset-cellQuestion mark>63}}!{{chset-left2|4_64}}{{chset-cell@|64}}{{chset-cellA|65}}{{chset-cellB|66}}{{chset-cellC|67}}{{chset-cellD|68}}{{chset-cellE|69}}{{chset-cellF|70}}{{chset-cellG|71}}{{chset-cellH|72}}{{chset-cellI|73}}{{chset-cellJ|74}}{{chset-cellK|75}}{{chset-cellL|76}}{{chset-cellM|77}}{{chset-cellN|78}}{{chset-cellO|79}}!{{chset-left2|5_80}}{{chset-cellP|80}}{{chset-cellQ|81}}{{chset-cellR|82}}{{chset-cellS|83}}{{chset-cellT|84}}{{chset-cellU|85}}{{chset-cellV|86}}{{chset-cellW|87}}{{chset-cellX|88}}{{chset-cellY|89}}{{chset-cellZ|90}}{{chset-cellLeft square bracket>91}}{{chset-cellBackslash>92}}{{chset-cellRight square bracket>93}}{{chset-cellCaret>94}}{{chset-cellUnderscore>95}}!{{chset-left2|6_96}}{{chset-cellGrave accent>96}}{{chset-cella|97}}{{chset-cellb|98}}{{chset-cellc|99}}{{chset-celld|100}}{{chset-celle|101}}{{chset-cellf|102}}{{chset-cellg|103}}{{chset-cellh|104}}{{chset-celli|105}}{{chset-cellj|106}}{{chset-cellk|107}}{{chset-celll|108}}{{chset-cellm|109}}{{chset-celln|110}}{{chset-cello|111}}!{{chset-left2|7_112}}{{chset-cellp|112}}{{chset-cellq|113}}{{chset-cellr|114}}{{chset-cells|115}}{{chset-cellt|116}}{{chset-cellu|117}}{{chset-cellv|118}}{{chset-cellw|119}}{{chset-cellx|120}}{{chset-celly|121}}{{chset-cellz|122}}{{chset-cellLeft curly bracket>123}}{{chset-cellVertical bar>124}}{{chset-cellRight curly bracket>125}}{{chset-cell~|126}}{{chset-ctrlDelete character>127}}{{Chset-legend|graybox=Character changed from 1963 version and/or 1965 draft}}


    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 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{{snd}} according to Bemer, "so much so that the code that was to become ASCII was first called the Bemer–Ross Code in Europe".WEB, Robert William Bemer, Bemer, Robert William,weblink Bemer meets Europe (Computer Standards) – Computer History Vignettes,, 2008-04-14, yes,weblink" title="">weblink 2013-10-17, (NB. Bemer was employed at IBM at that time.) Because of his extensive work on ASCII, Bemer has been called "the father of ASCII".WEB,weblink Robert William Bemer: Biography, 2013-03-09, no,weblink" title="">weblink 2016-06-16, On March 11, 1968, U.S. President Lyndon B. Johnson mandated that all computers purchased by the United States Federal Government support ASCII, stating:WEB, Memorandum Approving the Adoption by the Federal Government of a Standard Code for Information Interchange, Johnson, Lyndon Baines, Lyndon Baines Johnson, The American Presidency Project, 1968-03-11,weblink 2008-04-14, NEWSGROUP,weblink Re: Early history of ASCII?, Richard S. Shuford, December 20, 1996, alt.folklore.computers,, BOOK, McGraw-Hill Inc., Compilation of Data Communications Standards, Harold C., Folts, Harry, Karp, 1982-02-01, 2nd revised, 978-0-07-021457-6, 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 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.ASCII was the most common character encoding on the World Wide Web until December 2007, when UTF-8 encoding surpassed it; UTF-8 is backward compatible with ASCII.WEB, UTF-8 Growth on the Web, Dubost, Karl, 2008-05-06, W3C Blog, World Wide Web Consortium,weblink 2010-08-15, no,weblink 2016-06-16, WEB, Moving to Unicode 5.1, Davis, Mark, Mark Davis (Unicode), 2008-05-05, Official Google Blog,weblink 2010-08-15, no,weblink 2016-06-16, WEB, Unicode nearing 50% of the web, Davis, Mark, Mark Davis (Unicode), 2010-01-28, Official Google Blog,weblink 2010-08-15, no,weblink 2016-06-16,

    {{anchor|Variants}}Variants and derivations

    As computer technology spread throughout the world, different standards bodies and corporations developed many variations of ASCII to facilitate the expression of non-English languages that used Roman-based alphabets. One could class some of these variations as "ASCII extensions", although some misuse that term to represent all variants, including those that do not preserve ASCII's character-map in the 7-bit range. Furthermore, the ASCII extensions have also been mislabelled as ASCII.

    {{anchor|7-bit}}7-bit codes

    {{See also|UTF-7}}From early in its development,"Specific Criteria", attachment to memo from R. W. Reach, "X3-2 Meeting – September 14 and 15", September 18, 1961 ASCII was intended to be just one of several national variants of an international character code standard.Other international standards bodies have ratified character encodings such as ISO 646 (1967) that are identical or nearly identical to ASCII, with extensions for characters outside the English alphabet and symbols used outside the United States, such as the symbol for the United Kingdom's pound sterling (£). Almost every country needed an adapted version of ASCII, since ASCII suited the needs of only the US and a few other countries. For example, Canada had its own version that supported French characters.Many other countries developed variants of ASCII to include non-English letters (e.g. é, ñ, ß, Ł), currency symbols (e.g. £, ¥), etc. See also YUSCII (Yugoslavia).It would share most characters in common, but assign other locally useful characters to several code points reserved for "national use". However, the four years that elapsed between the publication of ASCII-1963 and ISO's first acceptance of an international recommendation during 1967{{citation |author-last=Maréchal |author-first=R. |title=ISO/TC 97 – Computers and Information Processing: Acceptance of Draft ISO Recommendation No. 1052 |date=1967-12-22}} caused ASCII's choices for the national use characters to seem to be de facto standards for the world, causing confusion and incompatibility once other countries did begin to make their own assignments to these code points.ISO/IEC 646, like ASCII, is a 7-bit character set. It does not make any additional codes available, so the same code points encoded different characters in different countries. Escape codes were defined to indicate which national variant applied to a piece of text, but they were rarely used, so it was often impossible to know what variant to work with and, therefore, which character a code represented, and in general, text-processing systems could cope with only one variant anyway.Because the bracket and brace characters of ASCII were assigned to "national use" code points that were used for accented letters in other national variants of ISO/IEC 646, a German, French, or Swedish, etc. programmer using their national variant of ISO/IEC 646, rather than ASCII, had to write, and thus read, something such as
    ä aÄiÜ = 'Ön'; ü
    instead of
    { a[i] = 'n'; }
    C trigraphs were created to solve this problem for ANSI C, although their late introduction and inconsistent implementation in compilers limited their use. Many programmers kept their computers on US-ASCII, so plain-text in Swedish, German etc. (for example, in e-mail or Usenet) contained "{, }" and similar variants in the middle of words, something those programmers got used to. For example, a Swedish programmer mailing another programmer asking if they should go for lunch, could get "N{ jag har sm|rg}sar" as the answer, which should be "Nä jag har smörgåsar" meaning "No I've got sandwiches".

    {{anchor|8-bit}}8-bit codes

    {{See also|UTF-8}}Eventually, as 8-, 16- and 32-bit (and later 64-bit) computers began to replace 12-, 18- and 36-bit computers as the norm, it became common to use an 8-bit byte to store each character in memory, providing an opportunity for extended, 8-bit relatives of ASCII. In most cases these developed as true extensions of ASCII, leaving the original character-mapping intact, but adding additional character definitions after the first 128 (i.e., 7-bit) characters.Encodings include ISCII (India), VISCII (Vietnam). Although these encodings are sometimes referred to as ASCII, true ASCII is defined strictly only by the ANSI standard.Most early home computer systems developed their own 8-bit character sets containing line-drawing and game glyphs, and often filled in some or all of the control characters from 0 to 31 with more graphics. Kaypro CP/M computers used the "upper" 128 characters for the Greek alphabet.The PETSCII code Commodore International used for their 8-bit systems is probably unique among post-1970 codes in being based on ASCII-1963, instead of the more common ASCII-1967, such as found on the ZX Spectrum computer. Atari 8-bit computers and Galaksija computers also used ASCII variants.The IBM PC defined code page 437, which replaced the control characters with graphic symbols such as smiley faces, and mapped additional graphic characters to the upper 128 positions. Operating systems such as DOS supported these code pages, and manufacturers of IBM PCs supported them in hardware. Digital Equipment Corporation developed the Multinational Character Set (DEC-MCS) for use in the popular VT220 terminal as one of the first extensions designed more for international languages than for block graphics. The Macintosh defined Mac OS Roman and Postscript also defined a set, both of these contained both international letters and typographic punctuation marks instead of graphics, more like modern character sets.The ISO/IEC 8859 standard (derived from the DEC-MCS) finally provided a standard that most systems copied (at least as accurately as they copied ASCII, but with many substitutions). A popular further extension designed by Microsoft, Windows-1252 (often mislabeled as ISO-8859-1), added the typographic punctuation marks needed for traditional text printing. ISO-8859-1, Windows-1252, and the original 7-bit ASCII were the most common character encodings until 2008 when UTF-8 became more common.ISO/IEC 4873 introduced 32 additional control codes defined in the 80–9F hexadecimal range, as part of extending the 7-bit ASCII encoding to become an 8-bit system.BOOK, The Unicode Consortium, Julie D., Allen, The Unicode standard, Version 5.0, 2006-10-27, Addison-Wesley Professional, Upper Saddle River, New Jersey, US, 978-0-321-48091-0,weblink 2015-03-13, Chapter 13: Special Areas and Format Characters, 314,


    {{See also|Basic Latin (Unicode block)}}Unicode and the ISO/IEC 10646 Universal Character Set (UCS) have a much wider array of characters and their various encoding forms have begun to supplant ISO/IEC 8859 and ASCII rapidly in many environments. While ASCII is limited to 128 characters, Unicode and the UCS support more characters by separating the concepts of unique identification (using natural numbers called code points) and encoding (to 8-, 16- or 32-bit binary formats, called UTF-8, UTF-16 and UTF-32).ASCII was incorporated into the Unicode (1991) character set as the first 128 symbols, so the 7-bit ASCII characters have the same numeric codes in both sets. This allows UTF-8 to be backward compatible with 7-bit ASCII, as a UTF-8 file containing only ASCII characters is identical to an ASCII file containing the same sequence of characters. Even more importantly, forward compatibility is ensured as software that recognizes only 7-bit ASCII characters as special and does not alter bytes with the highest bit set (as is often done to support 8-bit ASCII extensions such as ISO-8859-1) will preserve UTF-8 data unchanged.WEB, utf-8(7) â€“ Linux manual page,, 2014-02-26,weblink 2014-04-21,

    See also




    {{Reflist|40em|refs=BOOK, General Purpose Software, Chapter 1: Inside ASCII, Bemer, Robert William, Robert William Bemer, 1980, Best of Interface Age, 2, Portland, OR, USA, dilithium Press, 978-0-918398-37-6, 79-67462,weblink 2016-08-27, yes,weblink" title="">weblink August 27, 2016, 1–50, from:
    • JOURNAL, Inside ASCII – Part I, Bemer, Robert William, Robert William Bemer, Interface Age, 3, 5, May 1978, 96–102,
    • JOURNAL, Inside ASCII – Part II, Bemer, Robert William, Robert William Bemer, Interface Age, 3, 6, June 1978, 64–74,
    • JOURNAL, Inside ASCII – Part III, Bemer, Robert William, Robert William Bemer, Interface Age, 3, 7, July 1978, 80–87,

    Further reading

    • JOURNAL, A Proposal for Character Code Compatibility, Robert William, Bemer, Robert William Bemer, Communications of the ACM, 3, 2, 1960, 10.1145/366959.366961, 71–72,
    • WEB, The Babel of Codes Prior to ASCII: The 1960 Survey of Coded Character Sets: The Reasons for ASCII, Robert William, Bemer, Robert William Bemer, 2003-05-23,weblink 2016-05-09, yes,weblink" title="">weblink 2013-10-17, from:
      • JOURNAL, Survey of coded character representation, Robert William, Bemer, Robert William Bemer, Communications of the ACM, 3, 12, 639–641, December 1960, 10.1145/367487.367493,
      • JOURNAL, Survey of punched card codes, H. J., Smith, F. A., Williams, Communications of the ACM, 3, 12, 642, December 1960, 10.1145/367487.367491,
    • BOOK, American National Standard Code for Information Interchange, American National Standards Institute, 1977,
    • JOURNAL, History and impact of computer standards, G. S., Robinson, C., Cargill, Computer (magazine), Computer, 29, 10, 79–85, 1996, 10.1109/2.539725,
    • WEB, On the Early Development of ASCII – The History of ASCII, John F., Ptak, Ralph Elvin, Mullendore, JF Ptak Science Books, March 2012, 1964, 1963,weblink 2016-05-26, no,weblink" title="">weblink 2016-05-26,

    External links

    {{Commons category|ASCII}}
    • WEB, C0 Controls and Basic Latin – Range: 0000–007F, The Unicode Standard 8.0, 2015, 1991, Unicode, Inc.,weblink 2016-05-26, no,weblink" title="">weblink 2016-05-26,
    • JOURNAL, The Evolution of Character Codes, 1874–1968, Eric, Fischer,, weblink" title="https:/-/">weblink
    {{Character encodings|state=collapsed}}

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