ISO/IEC 646 ISO/IEC 646 ''Information technology — ISO 7-bit coded character set for information interchange'', is an International Organization for Standardization, ISO/International Electrotechnical Commission, IEC standard in the ...

(commonly known as

ASCII ASCII ( ), an acronym for American Standard Code for Information Interchange, is a character encoding standard for representing a particular set of 95 (English language focused) printable character, printable and 33 control character, control c ...

) and related standards including

ISO 8859 ISO/IEC 8859 is a joint International Organization for Standardization, ISO and International Electrotechnical Commission, IEC series of standards for 8-bit character encodings. The series of standards consists of numbered parts, such as ISO/IEC ...

and

Unicode Unicode or ''The Unicode Standard'' or TUS is a character encoding standard maintained by the Unicode Consortium designed to support the use of text in all of the world's writing systems that can be digitized. Version 16.0 defines 154,998 Char ...

, a graphic character, also known as printing character (or printable 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 any encoded character that is associated with one or more

glyph A glyph ( ) is any kind of purposeful mark. In typography, a glyph is "the specific shape, design, or representation of a character". It is a particular graphical representation, in a particular typeface, of an element of written language. A ...

ISO/IEC 646

In ISO 646, graphic characters are contained in rows 2 through 7 of the

code In communications and information processing, code is a system of rules to convert information—such as a letter, word, sound, image, or gesture—into another form, sometimes shortened or secret, for communication through a communicati ...

table. However, two of the characters in these rows, namely the

space character A whitespace character is a character data element that represents white space when text is rendered for display by a computer. For example, a ''space'' character (, ASCII 32) represents blank space such as a word divider in a Western scri ...

SP at row 2 column 0 and the delete character DEL (also called the rubout character) at row 7 column 15, require special mention. The space is considered to be ''both'' a graphic character and a control character in ISO 646. It can be considered as a character with a visible form or, in contexts such as

teleprinter 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- ...

s, a control character that advances the print head without printing a character. The delete character is strictly a control character, not a graphic character. This is true not only in ISO 646, but also in all related standards including Unicode. However, many other character sets deviate from ISO 646, and as a result a graphic character might occupy the position originally reserved for the delete character.

Unicode

In Unicode, Graphic characters are those with General Category Letter, Mark, Number, Punctuation, Symbol or Zs=space. Other code points (General categories Control, Zl=line separator, Zp=paragraph separator) are Format, Control, Private Use, Surrogate, Noncharacter or Reserved (unassigned).https://www.unicode.org/versions/Unicode5.2.0/ch02.pdf#G25564 Chapter 2, table 2.3

Spacing and non-spacing characters

Most graphic characters are spacing characters, which means that each instance of a spacing character has to occupy some

area Area is the measure of a region's size on a surface. The area of a plane region or ''plane area'' refers to the area of a shape or planar lamina, while '' surface area'' refers to the area of an open surface or the boundary of a three-di ...

in a graphic representation. For a

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 and point-to-multipoint configurations. Init ...

or a

typewriter A typewriter is a Machine, mechanical or electromechanical machine for typing characters. Typically, a typewriter has an array of Button (control), keys, and each one causes a different single character to be produced on paper by striking an i ...

this implies moving of the carriage after typing of a character. In the context of

text mode Text mode is a computer display mode in which content is internally represented on a computer screen in terms of characters rather than individual pixels. Typically, the screen consists of a uniform rectangular grid of ''character cells'', ea ...

display, each spacing character occupies one rectangular character box of equal sizes. Or maybe two adjacent ones, for non-alphabetic characters of East Asian languages. If a text is rendered using proportional fonts, widths of character boxes are not equal, but are positive. There exist also ''non-spacing'' graphic characters. Most of non-spacing characters are '' modifiers'', also called

combining character In digital typography, combining characters are Character (computing), characters that are intended to modify other characters. The most common combining characters in the Latin script are the combining diacritic, diacritical marks (including c ...

s in Unicode, such as

diacritic A diacritic (also diacritical mark, diacritical point, diacritical sign, or accent) is a glyph added to a letter or to a basic glyph. The term derives from the Ancient Greek (, "distinguishing"), from (, "to distinguish"). The word ''diacrit ...

al marks. Although non-spacing graphic characters are uncommon in traditional

code page In computing, a code page is a character encoding and as such it is a specific association of a set of printable character (computing), characters and control characters with unique numbers. Typically each number represents the binary value in a s ...

s, there are many such in Unicode. A combining character has its distinct glyph, but it applies to a character box of another character, a spacing one. In some historical systems such as

line printer A line printer Printer (computing), prints one entire line of text before advancing to another line. Most early line printers were printer (computing)#Impact printers, impact printers. Line printers are mostly associated with unit record eq ...

s this was implemented as

overstrike In typography, overstrike is a method of printing characters that are missing from the printer's character set. The character is created by placing one character on another one – for example, overstriking ⟨L⟩ with ⟨-⟩ results in prin ...

. Note that not all modifiers are non-spacing – there exists

Spacing Modifier Letters Spacing Modifier Letters is a Unicode block containing characters for the IPA, UPA, and other phonetic transcriptions. Included are the IPA tone marks, and modifiers for aspiration and palatalization. The word ''spacing'' indicates that these ...

Unicode block.

Notes

References

{{Reflist Character encoding

ISO/IEC 646

Unicode

Spacing and non-spacing characters

See also

Notes

References