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 ...

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 ...

) 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 ...

" 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
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
. 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 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) ...

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 ...

,
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 ...

,
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 ...

,
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
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 ...

,
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 ...

and
Windows
Microsoft Windows, commonly referred to as Windows, is a group of several proprietary
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