Ascii definition

ăskē
A standard computer code used to facilitate the interchange of information among various types of data-processing equipment.
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A standard for assigning numerical values to the set of letters in the Roman alphabet and typographic characters.
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A code that assigns the numbers 0 through 127 to the letters of the alphabet, the digits 0 through 9, punctuation marks, and certain other characters. For example, the capital letter A is coded as 65 (binary 1000001). By standardizing the values used to represent written text, ASCII enables computers to exchange information. Basic, or standard, ASCII uses seven bits for each character code, giving it 27 , or 128, unique symbols. Various larger character sets, called extended ASCII, use eight bits for each character, yielding 128 additional codes numbered 128 to 255.
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A standard coding scheme specifically oriented toward data processing applications, ASCII was developed in 1963 and modified in 1967 by the American National Standards Institute (ANSI). ASCII employs a 7-bit coding scheme, supporting 128 (2 7 ) characters, which is quite satisfactory for both upper case and lower case letters of the English alphabet and similarly simple Roman alphabets, Arabic numerals, punctuation marks, a reasonable complement of special characters, and a modest number of control characters. As ASCII was designed for use in asynchronous communications (involving non-IBM computers, in those days), relatively few control characters were required, making a 7-bit scheme acceptable. IBM computers, which were relatively complex mainframes, required the 8-bit EBCDIC coding scheme to accommodate the necessary complement of control characters.Table A-2 shows the ASCII code. Although the full explanations of all control codes are outside the scope of this book, the following control characters are representative: 1. NUL (NULl): A transmission control character used to serve a media-fill or time-fill requirement, i.e., a stuff character or padding character. 2. SOH (Start Of Header): A transmission control character that indicates the start of a message heading. 3. STX (Start of TeXt): A transmission control character that alerts the receiving device to start the reading, transmission, reception, or recording of text. 4. ETX (End of TeXt): A transmission control character that alerts the receiving device to terminate the reading, transmission, reception, or recording of text. 5. EOT (End Of Transmission): A transmission control character that alerts the receiving device to terminate a transmission that may include one or more texts or messages. 6. ENQ (ENQuiry): A transmission control character to request a response from a station to which a connection has been established.The request may be for the station identification, type of equipment, and station status. 7. NAK (Negative AcKnowledgement): A transmission control character sent by the receiving device to the transmitting device to indicate that a received block of data contained one or more errors. A NAK will trigger the transmitting device to retransmit that errored block. 8. ACK (ACKnowledgement): A transmission control character sent by the receiving device to the transmitting device to indicate that a received block of data contained no errors. 9. BEL (BELl): A transmission control character that alerts the receiving device that causes a bell to ring or activates some other audio or visual device to gain the attention of the operator at the receiving station. 10. ETB (End of Transmission Block): A code-extension character used to indicate the end of the transmission of a block of data. 11. CAN (CANcel): A transmission control character indicating that the associated data is in error or is to be ignored. 12. EM (End of Medium): A control character indicating the physical end of a data storage medium, or the usable portion of the medium. 13. SUB (SUBstitute): Used in place of a character that is known to be invalid, i.e., in error. Also used to indicate a character used in place of one that cannot be represented on a given device, e.g., e may be used in place of (epsilon) or d may be used in place of (delta). 14. ESC (ESCape): A code-extension character used to indicate a change in code interpretation to another character set, according to some convention or agreement.This is much like the use of the shift key in Baudot code to indicate a shift between figures and characters. 15. CR (Carriage Return): A format-control character that causes the print or display position to move to the first position, or left-hand margin, of the screen or print medium. Now often associated with an LF (Line Feed), which moves the print position down to the next line In Unicode terms, ASCII is known as Unicode Transformation Format-7 (UTF-7). See also asynchro-nous, code set, EBCDIC, and Unicode.
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(obsolete) Plural form of ascian.
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(computing) American Standard Code for Information Interchange.
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Origin of ascii

  • A(merican) S(tandard) C(ode for) I(nformation) I(nterchange)

    From American Heritage Dictionary of the English Language, 5th Edition

  • (computing) Alternative form of ASCII.

    From Wiktionary