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ASCII (American Standard Code for Information Interchange), generally pronounced , is a character encoding based on the English alphabet. more...
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ASCII codes represent text in computers, communications equipment, and other devices that work with text. Most modern character encodings—which support many more characters—have a historical basis in ASCII.
ASCII was first published as a standard in 1967 and was last updated in 1986. It currently defines codes for 33 non-printing, mostly obsolete control characters that affect how text is processed, plus the following 95 printable characters (starting with the space character):
Overview
Similar to other character representation computer codes, ASCII specifies a correspondence between digital bit patterns and the symbols/glyphs of a written language, thus allowing digital devices to communicate with each other and to process, store, and communicate character-oriented information. The ASCII character encoding — or a compatible extension (see below) — is used on nearly all common computers, especially personal computers and workstations. The preferred MIME name for this encoding is "US-ASCII".
ASCII is, strictly, a seven-bit code, meaning that it uses the bit patterns representable with seven binary digits (a range of 0 to 127 decimal) to represent character information. At the time ASCII was introduced, many computers dealt with eight-bit groups (bytes or, more specifically, octets) as the smallest unit of information; the eighth bit was commonly used as a parity bit for error checking on communication lines or other device-specific functions. Machines which did not use parity typically set the eighth bit to zero, though some systems such as Prime machines running PRIMOS set the eighth bit of ASCII characters to one.
ASCII only defines a relationship between specific characters and bit sequences; aside from reserving a few control codes for line-oriented formatting, it does not define any mechanism for describing the structure or appearance of text within a document. Such concepts are within the realm of other systems such as the markup languages.
History
ASCII developed from telegraphic codes and first entered commercial use as a seven-bit teleprinter code promoted by Bell data services. The Bell System had previously planned to use a six-bit code, derived from Fieldata, that added punctuation and lower-case letters to the earlier five-bit Baudot teleprinter code, but was persuaded instead to join the ASA subcommittee that had started to develop ASCII. Baudot helped in the automation of sending and receiving telegraphic messages, and took many features from Morse code; however, unlike Morse code, Baudot used constant-length codes. Compared to earlier telegraph codes, the proposed Bell code and ASCII both underwent re-ordering for more convenient sorting (especially alphabetization) of lists, and added features for devices other than teleprinters. Bob Bemer introduced features such as the 'escape sequence'. His British colleague Hugh McGregor Ross helped to popularize this work, as Bemer said, "so much so that the code that was to become ASCII was first called the Bemer-Ross Code in Europe".
Read more at Wikipedia.org
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