HOME

TheInfoList




In
computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithmic processes and development of both computer hardware , hardware and software. It has sci ...

computing
and
telecommunication Telecommunication is the transmission of information by various types of technologies over wire A wire is a single usually cylindrical A cylinder (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Gr ...
, a control
character Character(s) may refer to: Arts, entertainment, and media Literature * ''Character'' (novel), a 1936 Dutch novel by Ferdinand Bordewijk * ''Characters'' (Theophrastus), a classical Greek set of character sketches attributed to Theophrastus M ...
or non-printing character (NPC) is a
code point In character encoding In computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithmic processes and development of both computer hardw ...
(a
number A number is a mathematical object A mathematical object is an abstract concept arising in mathematics. In the usual language of mathematics, an ''object'' is anything that has been (or could be) formally defined, and with which one may do deduct ...

number
) in a
character set Character encoding is the process of assigning numbers to Graphics, graphical character (computing), characters, especially the written characters of Language, human language, allowing them to be Data storage, stored, Data communication, transmit ...
, that does not represent a written symbol. They are used as
in-band signaling In telecommunications Telecommunication is the transmission of information by various types of technologies over wire, radio, Optical system, optical, or other Electromagnetism, electromagnetic systems. It has its origin in the desire of hu ...
to cause effects other than the addition of a symbol to the text. All other characters are mainly printing, printable, or
graphic character In ISO/IEC 646 (commonly known as ASCII) and related standards including ISO 8859 and Unicode, a graphic character is any character intended to be written, printed, or otherwise displayed in a form that can be read by humans. In other words, it is ...
s, except perhaps for the "
space Space is the boundless extent in which and events have relative and . In , physical space is often conceived in three s, although modern s usually consider it, with , to be part of a boundless known as . The concept of space is considere ...

space
" character (see ASCII printable characters). All entries in the
ASCII ASCII ( ), abbreviated from American Standard Code for Information Interchange, is a character encoding In computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the stu ...
table below code 32 (technically the C0 control code set) are of this kind, including
CR and LF
CR and LF
used to separate lines of text. The code 127 (
DEL Del, or nabla, is an operator used in mathematics (particularly in vector calculus Vector calculus, or vector analysis, is concerned with derivative, differentiation and integral, integration of vector fields, primarily in 3-dimensional ...
) is also a control character.
Extended ASCII Extended ASCII (EASCII or high ASCII) character encoding Character encoding is the process of assigning numbers to Graphics, graphical character (computing), characters, especially the written characters of Language, human language, allowing th ...
sets defined by
ISO 8859 ISO/IEC 8859 is a joint ISO The International Organization for Standardization (ISO; ) is an international standard are technical standards developed by international organizations (intergovernmental organizations), such as Codex Alimentarius ...
added the codes 128 through 159 as control characters, this was primarily done so that if the high bit was stripped it would not change a printing character to a C0 control code, but there have been some assignments here, in particular
NEL
NEL
. This second set is called the C1 set. These 65 control codes were carried over to
Unicode Unicode, formally the Unicode Standard, is an information technology standard Standard may refer to: Flags * Colours, standards and guidons * Standard (flag), a type of flag used for personal identification Norm, convention or requireme ...

Unicode
. Unicode added more characters that could be considered controls, but it makes a distinction between these "Formatting characters" (such as the
zero-width non-joiner The zero-width non-joiner (ZWNJ) is a non-printing character used in the computerization of writing system A writing system is a method of visually representing verbal communication Communication (from Latin ''communicare'', meaning "to sh ...
), and the 65 control characters. The
Extended Binary Coded Decimal Interchange Code Extended Binary Coded Decimal Interchange Code (EBCDIC; ) is an eight-bit character encoding used mainly on IBM mainframe and IBM midrange computer operating systems. It descended from the code used with punched cards and the corresponding six-b ...
(EBCDIC) character set contains 65 control codes, including all of the ASCII control codes plus additional codes which are mostly used to control IBM peripherals.


History

Procedural signs in
Morse code Morse code is a method used in telecommunication to Character encoding, encode Written language, text characters as standardized sequences of two different signal durations, called ''dots'' and ''dashes'', or ''dits'' and ''dahs''. Morse code ...
are a form of control character. A form of control characters were introduced in the 1870
Baudot code The Baudot code is an early character encoding In computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithmic processes and developme ...
: NUL and DEL. The 1901
Murray code The Baudot code is an early character encoding for telegraphy invented by Émile Baudot in the 1870s. It was the predecessor to the International Telegraph Alphabet No. 2 (ITA2), the most common teleprinter code in use until the advent of ASCII. ...
added the
carriage return A carriage return, sometimes known as a cartridge return and often shortened to CR, or return, is a control character In computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It inclu ...
(CR) and
line feed Newline (frequently called line ending, end of line (EOL), next line (NEL) or line break) is a control character In computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes ...
(LF), and other versions of the Baudot code included other control characters. The
bell character A bell code (sometimes bell character) is a device control code In computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithmic processe ...
(BEL), which rang a bell to alert operators, was also an early
teletype A teleprinter (teletypewriter, teletype or TTY) is an electromechanical device that can be used to send and receive typed messages through various communications channels, in both point-to-point (telecommunications), point-to-point and point-t ...
control character. Control characters have also been called "format effectors".


In ASCII

The control characters in ASCII still in common use include: * 0 ( null, NUL, \0, ^@), originally intended to be an ignored character, but now used by many
programming language A programming language is a formal language In logic, mathematics, computer science, and linguistics, a formal language consists of string (computer science), words whose symbol (formal), letters are taken from an alphabet (computer science) ...

programming language
s including C to mark the end of a string. * 7 (
bell A bell is a struck idiophone, directly struck idiophone percussion instrument. Most bells have the shape of a hollow cup that when struck vibrates in a single strong strike tone, with its sides forming an efficient resonator. The strike may be ...
, BEL, \a, ^G), which may cause the device to emit a warning such as a bell or beep sound or the screen flashing. * 8 (
backspace Backspace () is the keyboard key that originally pushed the typewriter Video showing the operation of a typewriter A typewriter is a mechanical Mechanical may refer to: Machine * Mechanical system A machine is any physical system with ...

backspace
, BS, \b, ^H), may overprint the previous character. * 9 (
horizontal tab Image:Keyboard-left keys.jpg, Tab key (top left) on a standard Windows keyboard The tab key (abbreviation of tabulator key or tabular key) on a alphanumeric keyboard, keyboard is used to advance the cursor to the next tab stop. History The wo ...

horizontal tab
, HT, \t, ^I), moves the printing position right to the next tab stop. * 10 (
line feed Newline (frequently called line ending, end of line (EOL), next line (NEL) or line break) is a control character In computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includ ...

line feed
, LF, \n, ^J), moves the print head down one line, or to the left edge and down. Used as the end of line marker in most
UNIX systems
UNIX systems
and variants. * 11 (
vertical tab Image:Keyboard-left keys.jpg, Tab key (top left) on a standard Windows keyboard The tab key (abbreviation of tabulator key or tabular key) on a alphanumeric keyboard, keyboard is used to advance the cursor to the next tab stop. History The wo ...

vertical tab
, VT, \v, ^K), vertical tabulation. * 12 (
form feed A page break is a marker in an electronic document A document is a writing, written, drawing, drawn, presented, or memorialized representation of thought, often the manifestation of nonfiction, non-fictional, as well as fictional, content. T ...
, FF, \f, ^L), to cause a printer to eject paper to the top of the next page, or a video terminal to clear the screen. * 13 (
carriage return A carriage return, sometimes known as a cartridge return and often shortened to CR, or return, is a control character In computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It inclu ...
, CR, \r, ^M), moves the printing position to the start of the line, allowing overprinting. Used as the end of line marker in
Classic Mac OS The classic Mac OS (System Software) is the series of operating system An operating system (OS) is system software System software is software designed to provide a platform for other software. Examples of system software include operatin ...
,
OS-9 OS-9 is a family of real-time, process-based, multitasking, multi-user Multi-user software is software, computer software that allows access by multiple User (computing), users of a computer. Time-sharing systems are multi-user systems. Mos ...
, FLEX (and variants). A CR+LF pair is used by
CP/M CP/M, originally standing for Control Program/Monitor and later Control Program for Microcomputers, is a mass-market operating system An operating system (OS) is system software System software is software designed to provide a platform ...
-80 and its derivatives including
DOS DOS (, ) is a platform-independent acronym for disk operating system which later became a common shorthand for disk-based operating systems on IBM PC compatible IBM PC compatible computers are similar to the original IBM Personal Computer, IB ...

DOS
and
Windows Microsoft Windows, commonly referred to as Windows, is a group of several proprietary {{Short pages monitor