Characters per line
Encyclopedia
In typography
and computing
characters per line (CPL) or terminal width refers to the maximal number of monospaced characters that may appear on a single line
. It is similar to line length
in typesetting.
age, most designs were geared toward 72 CPL, derived from a pitch of 12 characters per inch, multiplied by 6 inches (see for example IBM Selectric). This would ensure at least 1 inch for each margin, with the U.S. government at the time having standardized on 8×11" paper
. Early computer text editor
s used this measure as a baseline for their terminal interfaces. Other common measures were 80 CPL (historically descended from punched card
s and later broadly used in monitor text mode
), 40 CPL (in low-resolution screens) and 132 CPL.
| bgcolor=#000000 |
|-
|+ align=bottom |RFC 2046, which defines the text/plain MIME type, is itself a 72 CPL plain text. Top of page 3
|}>
With the advent of desktop computing and publishing, and technologies such as TrueType
used in word processing
and web browsing
, a uniform CPL has been made mostly obsolete. HTML
(and some other modern text presentation formats) uses dynamic word wrap
ping which is more flexible than characters per line restriction and may produce even a text block with non-rectangular shape, just like in paper typesetting
.
Many plain text
documents still conform to 72 CPL out of tradition.
found that CPL had only small effects on readability, including factors of speed and comprehension. When asked for preferences, however, 60% of respondents indicated a preference for either the shortest (35 CPL) or longest (95 CPL) lines used in the study. At the same time, 100% of respondents selected either one of these quantities as being the least desirable.
Typography
Typography is the art and technique of arranging type in order to make language visible. The arrangement of type involves the selection of typefaces, point size, line length, leading , adjusting the spaces between groups of letters and adjusting the space between pairs of letters...
and computing
Computing
Computing is usually defined as the activity of using and improving computer hardware and software. It is the computer-specific part of information technology...
characters per line (CPL) or terminal width refers to the maximal number of monospaced characters that may appear on a single line
Plain text
In computing, plain text is the contents of an ordinary sequential file readable as textual material without much processing, usually opposed to formatted text....
. It is similar to line length
Line length
In Typography Line length is the width occupied by a block of typeset text, measured in inches, picas and points. A block of text or paragraph has a maximum line length that fits a determined design....
in typesetting.
History
At the end of the typewriterTypewriter
A typewriter is a mechanical or electromechanical device with keys that, when pressed, cause characters to be printed on a medium, usually paper. Typically one character is printed per keypress, and the machine prints the characters by making ink impressions of type elements similar to the pieces...
age, most designs were geared toward 72 CPL, derived from a pitch of 12 characters per inch, multiplied by 6 inches (see for example IBM Selectric). This would ensure at least 1 inch for each margin, with the U.S. government at the time having standardized on 8×11" paper
Letter (paper size)
Letter or US Letter is the most common paper size for office use in several countries, including the United States, Canada, Mexico, Bolivia, Colombia, Venezuela, the Philippines, and Chile. It measures 8.5 by 11 inches ....
. Early computer text editor
Text editor
A text editor is a type of program used for editing plain text files.Text editors are often provided with operating systems or software development packages, and can be used to change configuration files and programming language source code....
s used this measure as a baseline for their terminal interfaces. Other common measures were 80 CPL (historically descended from punched card
Punched card
A punched card, punch card, IBM card, or Hollerith card is a piece of stiff paper that contains digital information represented by the presence or absence of holes in predefined positions...
s and later broadly used in monitor text mode
Text mode
Text mode is a kind of computer display mode in which the content of the screen is internally represented in terms of characters rather than individual pixels. Typically, the screen consists of a uniform rectangular grid of character cells, each of which contains one of the characters of a...
), 40 CPL (in low-resolution screens) and 132 CPL.
In modern computing
|-
|+ align=bottom |RFC 2046, which defines the text/plain MIME type, is itself a 72 CPL plain text. Top of page 3
|}>
With the advent of desktop computing and publishing, and technologies such as TrueType
TrueType
TrueType is an outline font standard originally developed by Apple Computer in the late 1980s as a competitor to Adobe's Type 1 fonts used in PostScript...
used in word processing
Word processor
A word processor is a computer application used for the production of any sort of printable material....
and web browsing
Web browser
A web browser is a software application for retrieving, presenting, and traversing information resources on the World Wide Web. An information resource is identified by a Uniform Resource Identifier and may be a web page, image, video, or other piece of content...
, a uniform CPL has been made mostly obsolete. HTML
HTML
HyperText Markup Language is the predominant markup language for web pages. HTML elements are the basic building-blocks of webpages....
(and some other modern text presentation formats) uses dynamic word wrap
Word wrap
In text display, line wrap is the feature of continuing on a new line when a line is full, such that each line fits in the viewable window, allowing text to be read from top to bottom without any horizontal scrolling....
ping which is more flexible than characters per line restriction and may produce even a text block with non-rectangular shape, just like in paper typesetting
Typesetting
Typesetting is the composition of text by means of types.Typesetting requires the prior process of designing a font and storing it in some manner...
.
Many plain text
Plain text
In computing, plain text is the contents of an ordinary sequential file readable as textual material without much processing, usually opposed to formatted text....
documents still conform to 72 CPL out of tradition.
Human perception
A study at Wichita State UniversityWichita State University
Wichita State University is a NCAA Division I public university in Wichita, Kansas with selective admissions. WSU is one of six state universities governed by the Kansas Board of Regents. The current president is Dr. Donald Beggs....
found that CPL had only small effects on readability, including factors of speed and comprehension. When asked for preferences, however, 60% of respondents indicated a preference for either the shortest (35 CPL) or longest (95 CPL) lines used in the study. At the same time, 100% of respondents selected either one of these quantities as being the least desirable.
See also
- IBM 80-column punched card format