资料来源 : WordNet®

American Standard Code for Information Interchange
     n : (computer science) a code for information exchange between
         computers made by different companies; a string of 7
         binary digits represents each character; used in most
         microcomputers [syn: {ASCII}]

资料来源 : Free On-Line Dictionary of Computing

American Standard Code for Information Interchange
     
        The basis of character sets used in almost all present-day
        computers.  {US-ASCII} uses only the lower seven {bit}s
        ({character points} 0 to 127) to convey some {control codes},
        space, numbers, most basic punctuation, and unaccented letters
        a-z and A-Z.  More modern coded character sets (e.g.,
        {Latin-1}, {Unicode}) define extensions to ASCII for values
        above 127 for conveying special Latin characters (like
        accented characters, or German ess-tsett), characters from
        non-Latin writing systems (e.g., Cyrillic, or {Han
        characters}), and such desirable {glyphs} as distinct open-
        and close-quotation marks.  ASCII replaced earlier systems
        such as {EBCDIC} and {Baudot}, which used fewer bytes, but
        were each {broken} in their own way.
     
        Computers are much pickier about spelling than humans; thus,
        hackers need to be very precise when talking about characters,
        and have developed a considerable amount of verbal shorthand
        for them.  Every character has one or more names - some
        formal, some concise, some silly.
     
        Individual characters are listed in this dictionary with
        alternative names from revision 2.3 of the {Usenet} ASCII
        pronunciation guide in rough order of popularity, including
        their official {ITU-T} names and the particularly silly names
        introduced by {INTERCAL}.
     
        See {V} {ampersand}, {asterisk}, {back quote}, {backslash},
        {caret}, {colon}, {comma}, {commercial at}, {control-C},
        {dollar}, {dot}, {double quote}, {equals}, {exclamation mark},
        {greater than}, {hash}, {left bracket}, {left parenthesis},
        {less than}, {minus}, {parentheses}, {oblique stroke},
        {percent}, {plus}, {question mark}, {right brace}, {right
        brace}, {right bracket}, {right parenthesis}, {semicolon},
        {single quote}, {space}, {tilde}, {underscore}, {vertical
        bar}, {zero}.
     
        Some other common usages cause odd overlaps.  The "#", "$",
        ">", and "&" characters, for example, are all pronounced "hex"
        in different communities because various assemblers use them
        as a prefix tag for {hexadecimal} constants (in particular,
        "#" in many assembler-programming cultures, "$" in the {6502}
        world, ">" at {Texas Instruments}, and "&" on the {BBC Micro},
        {Acorn Archimedes}, {Sinclair}, and some {Zilog Z80}
        machines).  See also {splat}.
     
        The inability of {US-ASCII} to correctly represent nearly any
        language other than English became an obvious and intolerable
        {misfeature} as computer use outside the US and UK became the
        rule rather than the exception (see {software rot}).  And so
        national extensions to US-ASCII were developed, such as
        Latin-1.
     
        Hardware and software from the US still tends to embody the
        assumption that US-ASCII is the universal character set and
        that words of text consist entirely of byte values 65-90 and
        97-122 (A-Z and a-z); this is a major irritant to people who
        want to use a character set suited to their own languages.
        Perversely, though, efforts to solve this problem by
        proliferating sets of national characters produced an
        evolutionary pressure (especially in protocol design, e.g.,
        the {URL} standard) to stick to {US-ASCII} as a subset common
        to all those in use, and therefore to stick to English as the
        language encodable with the common subset of all the ASCII
        dialects.  This basic problem with having a multiplicity of
        national character sets ended up being a prime justification
        for {Unicode}, which was designed, ostensibly, to be the *one*
        ASCII extension anyone will need.
     
        A system is described as "{eight-bit clean}" if it doesn't
        mangle text with byte values above 127, as some older systems
        did.
     
        See also {ASCII character table}, {Yu-Shiang Whole Fish}.
     
        (1995-03-06)