Difference between revisions of "ASCII"

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'''ASCII''' is a common historical [[character encoding]], designed to represent US English text in digital form. The acronym stands for [[America]]n [[Standard]] [[Code]] for [[Information]] [[Interchange]]. Most of the character encodings in use today are [[proper superset]]s of ASCII: these include the [[ISO 8859]] family of encodings, the [[Windows 1252]] code page, and [[Unicode]].
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'''ASCII''' is a common historical [[character encoding]], designed to represent US English text in digital form. The acronym stands for American Standard Code for Information Interchange. Most of the character encodings in common current use are [[proper superset]]s of ASCII: these include the [[ISO 8859]] family of encodings, the [[Windows 1252]] code page and the [[UTF-8]] encoding of the [[Unicode]] character set.
  
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In ASCII, each letter or number on the [[keyboard]] is assigned a number from 0 to 127. For example, "A" is assigned the value 65, "B" is assigned 66, and "C" is assigned 67, so the word "[[cab]]" would be represented in ASCII as "67 65 66".  As well as the 26 letters of the [[English alphabet]] and the [[number]]s from 0 to 9, many common [[punctuation]] symbols are assigned codes.  
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Each character is assigned a number from 0 to 127, encoded in [[binary]].  In addition to the 26 letters of the [[Alphabet#English Alphabet|English alphabet]] in upper and lower case and all ten digits, many common punctuation symbols are assigned codes, as are [[control characters]], such as backspace, carriage return and linefeed.
  
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ASCII was originally designed to work on [[mainframe]] computers, so naturally the first 31 ASCII values were assigned to "[[control character]]s", such as [[carriage return]] and [[line feed]], which were used to manipulate early [[teletype]] machines (a kind of [[printer]]). Most of these early ASCII "control characters" have become obsolete, and many modern ASCII implementations do not even bother to assign them, preferring to start the mapping at 32 (ASCII [[space]]).
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Because there are 128 separate codes, each ASCII character can be represented by 7 [[bit]]s.  Since one byte (8 bits) is allocated for each character, this leaves room for one [[checksum]] digit to guarantee that the character has not been corrupted in transmission or storage.
  
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Because there are 128 separate codes, an ASCII character can be represented by a [[signed char]] type in the [[C]] programming language.
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An ASCII character can be represented by a [[signed char]] type in the [[C]] programming language.
  
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[[Category:Information technology]]
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*[http://www.asciitable.com/ The complete ASCII code].  Note that this table gives the [[hexadecimal]] values for the characters ''without'' a checksum digit; the hexadecimal values actually stored are almost always different.
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[[Category:Information Technology]]
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[[Category:Communication]]

Latest revision as of 12:35, March 25, 2017

ASCII is a common historical character encoding, designed to represent US English text in digital form. The acronym stands for American Standard Code for Information Interchange. Most of the character encodings in common current use are proper supersets of ASCII: these include the ISO 8859 family of encodings, the Windows 1252 code page and the UTF-8 encoding of the Unicode character set.

Each character is assigned a number from 0 to 127, encoded in binary. In addition to the 26 letters of the English alphabet in upper and lower case and all ten digits, many common punctuation symbols are assigned codes, as are control characters, such as backspace, carriage return and linefeed.

Because there are 128 separate codes, each ASCII character can be represented by 7 bits. Since one byte (8 bits) is allocated for each character, this leaves room for one checksum digit to guarantee that the character has not been corrupted in transmission or storage.

An ASCII character can be represented by a signed char type in the C programming language.

  • The complete ASCII code. Note that this table gives the hexadecimal values for the characters without a checksum digit; the hexadecimal values actually stored are almost always different.
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