ASCII, an acronym for American Standard Code for Information Interchange, is a character encoding standard for electronic communication. ASCII codes represent text in computers, telecommunications equipment, and other devices. Because of technical limitations of computer systems at the time it was invented, ASCII has just 128 code points, of which only 95 are printable characters, which severely limited its scope. Modern computer systems have evolved to use Unicode, which has millions of code points, but the first 128 of these are the same as the ASCII set.
In computing and telecommunication, a control character or non-printing character (NPC) is a code point in a character set that does not represent a written character or symbol. They are used as in-band signaling to cause effects other than the addition of a symbol to the text. All other characters are mainly graphic characters, also known as printing characters, except perhaps for "space" characters. In the ASCII standard there are 33 control characters, such as code 7, BEL, which rings a terminal bell.
ISO/IEC 646 is a set of ISO/IEC standards, described as Information technology — ISO 7-bit coded character set for information interchange and developed in cooperation with ASCII at least since 1964. Since its first edition in 1967 it has specified a 7-bit character code from which several national standards are derived.
ISO/IEC 2022Information technology—Character code structure and extension techniques, is an ISO/IEC standard in the field of character encoding. It is equivalent to the ECMA standard ECMA-35, the ANSI standard ANSI X3.41 and the Japanese Industrial Standard JIS X 0202. Originating in 1971, it was most recently revised in 1994.
Extended Unix Code (EUC) is a multibyte character encoding system used primarily for Japanese, Korean, and simplified Chinese (characters).
GB/T 2312-1980 is a key official character set of the People's Republic of China, used for Simplified Chinese characters. GB2312 is the registered internet name for EUC-CN, which is its usual encoded form. GB refers to the Guobiao standards (国家标准), whereas the T suffix denotes a non-mandatory standard.
The ATASCII character set, from ATARI Standard Code for Information Interchange, alternatively ATARI ASCII, is a character encoding used in the Atari 8-bit home computers. ATASCII is based on ASCII, but is not fully compatible with it.
ArmSCII or ARMSCII is a set of obsolete single-byte character encodings for the Armenian alphabet defined by Armenian national standard 166–9. ArmSCII is an acronym for Armenian Standard Code for Information Interchange, similar to ASCII for the American standard. It has been superseded by the Unicode standard.
The C0 and C1 control code or control character sets define control codes for use in text by computer systems that use ASCII and derivatives of ASCII. The codes represent additional information about the text, such as the position of a cursor, an instruction to start a new line, or a message that the text has been received.
T.51 / ISO/IEC 6937:2001, Information technology — Coded graphic character set for text communication — Latin alphabet, is a multibyte extension of ASCII, or more precisely ISO/IEC 646-IRV. It was developed in common with ITU-T for telematic services under the name of T.51, and first became an ISO standard in 1983. Certain byte codes are used as lead bytes for letters with diacritics (accents). The value of the lead byte often indicates which diacritic that the letter has, and the follow byte then has the ASCII-value for the letter that the diacritic is on.
JIS X 0201, a Japanese Industrial Standard developed in 1969, was the first Japanese electronic character set to become widely used. The character set was initially known as JIS C 6220 before the JIS category reform. Its two forms were a 7-bit encoding or an 8-bit encoding, although the 8-bit form was dominant until Unicode replaced it. The full name of this standard is 7-bit and 8-bit coded character sets for information interchange (7ビット及び8ビットの情報交換用符号化文字集合).
The Unicode Consortium and the ISO/IEC JTC 1/SC 2/WG 2 jointly collaborate on the list of the characters in the Universal Coded Character Set. The Universal Coded Character Set, most commonly called the Universal Character Set, is an international standard to map characters, discrete symbols used in natural language, mathematics, music, and other domains, to unique machine-readable data values. By creating this mapping, the UCS enables computer software vendors to interoperate, and transmit—interchange—UCS-encoded text strings from one to another. Because it is a universal map, it can be used to represent multiple languages at the same time. This avoids the confusion of using multiple legacy character encodings, which can result in the same sequence of codes having multiple interpretations depending on the character encoding in use, resulting in mojibake if the wrong one is chosen.
Many Unicode characters are used to control the interpretation or display of text, but these characters themselves have no visual or spatial representation. For example, the null character is used in C-programming application environments to indicate the end of a string of characters. In this way, these programs only require a single starting memory address for a string, since the string ends once the program reads the null character.
OCR-A is a font issued in 1966 and first implemented in 1968. A special font was needed in the early days of computer optical character recognition, when there was a need for a font that could be recognized not only by the computers of that day, but also by humans. OCR-A uses simple, thick strokes to form recognizable characters. The font is monospaced (fixed-width), with the printer required to place glyphs 0.254 cm apart, and the reader required to accept any spacing between 0.2286 cm and 0.4572 cm.
Extended ASCII is a repertoire of character encodings that include the original 96 ASCII character set, plus up to 128 additional characters. There is no formal definition of "extended ASCII", and even use of the term is sometimes criticized, because it can be mistakenly interpreted to mean that the American National Standards Institute (ANSI) had updated its ANSI X3.4-1986 standard to include more characters, or that the term identifies a single unambiguous encoding, neither of which is the case.
KPS 9566 is a North Korean standard specifying a character encoding for the Chosŏn'gŭl (Hangul) writing system used for the Korean language. The edition of 1997 specified an ISO 2022-compliant 94×94 two-byte coded character set. Subsequent editions have added additional encoded characters outside of the 94×94 plane, in a manner comparable to UHC or GBK.
JIS X 0208 is a 2-byte character set specified as a Japanese Industrial Standard, containing 6879 graphic characters suitable for writing text, place names, personal names, and so forth in the Japanese language. The official title of the current standard is 7-bit and 8-bit double byte coded KANJI sets for information interchange. It was originally established as JIS C 6226 in 1978, and has been revised in 1983, 1990, and 1997. It is also called Code page 952 by IBM. The 1978 version is also called Code page 955 by IBM.
ISO 2047 is a standard for graphical representation of the control characters for debugging purposes, such as may be found in the character generator of a computer terminal; it also establishes a two-letter abbreviation of each control character. The graphics and two-letter codes are essentially unchanged from the 1968 European standard ECMA-17 and the 1973 American standard ANSI X3.32-1973. It became an ISO standard in 1975. It is also standardized as GB/T 3911-1983 in China, as KS X 1010 in Korea, and was enacted in Japan as "graphical representation of information exchange capabilities for character" JIS X 0209:1976.
ISO/IEC 10367:1991 is a standard developed by ISO/IEC JTC 1/SC 2, defining graphical character sets for use in character encodings implementing levels 2 and 3 of ISO/IEC 4873.
Code page 897 is IBM's implementation of the 8-bit form of JIS X 0201. It includes several additional graphical characters in the C0 control characters area, and the code points in question may be used as control characters or graphical characters depending on the context, similarly in concept to OEM-US, but with different graphical characters. The C0 rows are shown below.
