ascii history

ASCII is, strictly, a seven-bit code, meaning it uses patterns of seven binary digits (a range of 0 to 127 decimal) to represent each character. When ASCII was introduced, many computers used eight-bit bytes (groups of bits), also called octets, as the native data type. In seven-bit ASCII encoding, the eighth bit was commonly used as a parity bit for error checking on communication lines or for other device-specific functions. Machines that did not use parity checking typically set the eighth bit to 0.

The American National Standards Institute (then called the American Standards Association or ASA, and later the United States of America Standards Institute or USASI) developed ASCII based on earlier teleprinter encoding systems. Circa 1956, Ivan Idelson, at Ferranti in the UK, had proposed the Cluff-Foster-Idelson coding of characters on 7 track paper tape to a British Standards committee. This was one of the influences on ASCII. ASCII itself first entered commercial use in 1963 as a seven-bit teleprinter code for American Telephone & Telegraph's TWX (Teletype Wide-area eXchange) network. TWX originally used the earlier five-bit Baudot code, which was also used by the competing Telex teleprinter system. The Bell System had planned to upgrade to a six-bit code derived from the Fieldata project, which contained many punctuation and control characters that the Baudot code did not, but was persuaded instead to join the American Standards Association (part of ANSI) subcommittee that had started to develop ASCII.[citation needed] Compared with 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.[7] His British colleague Hugh McGregor Ross helped to popularize this work — according to Bemer, "so much so that the code that was to become ASCII was first called the Bemer-Ross Code in Europe".

ASCII was published as ASA X3.4-1963 and then subsequently updated as USASI X3.4-1967, USASI X3.4-1968, ANSI X3.4-1977, and finally, ANSI X3.4-1986.

Other international standards bodies have ratified character encodings such as ISO/IEC 646 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 only suited the needs of the USA and a few other countries. For example, Canada had its own version that supported French. Although these encodings are sometimes referred to as ASCII, true ASCII is strictly defined only by ANSI standard.

ASCII has been incorporated into the Unicode character set as the first 128 symbols, so the ASCII characters have the same numeric codes in both sets. This allows UTF-8 to be backward compatible with ASCII, a significant advantage.