A monospaced font, also called a fixed-pitch or non-proportional font, is a font whose letters and characters each occupy the same amount of horizontal space. This contrasts to variable-width fonts, where the letters differ in size to one another.
The first monospaced typefaces were designed for typewriters, which could only move the same distance forward with each letter typed. This also meant that monospaced fonts need not be typeset like variable width fonts and were, arguably, easier to deal with.
Note that this article generally assumes Western (Latin-based, Cyrillic, or Greek) writing systems. East Asian rules of typography, for example, require CJK fonts to always be monospaced at least as far as the main characters for writing words (i.e. not punctuation) are concerned. Other scripts vary in their use of monospaced fonts. There's an attempt of monospaced Arabic font – "Simplified Arabic Fixed".
Use in computers
Monospaced fonts were widely used in early computers and computer terminals, which often had extremely limited graphical capabilities. Hardware implementation was simplified by using a text mode where the screen layout was addressed as a regular grid of tiles, each of which could be set to display a character by indexing into the hardware's character map. Some systems allowed colored text to be displayed by varying the foreground and background color for each tile. Other effects included reverse video and blinking text. Nevertheless, these early systems were typically limited to a single console font.
Even though computers can now display a wide variety of fonts, almost every commercial IDE and software text editor employs a monospaced font as the default typeface. This increases the readability of source code, which is often heavily reliant on distinctions involving individual symbols. Monospaced fonts are also used in terminal emulation and for laying out tabulated data in plain text documents. In technical manuals and resources for programming languages, a monospaced font is often used to distinguish code from natural language text.
The term modern is sometimes used as a synonym for monospace generic font family. The term modern can be used for a fixed-pitch generic font family name used in OpenDocument format (ISO/IEC 26300:2006) and Rich Text Format.
Use in ASCII art
A monospaced font is often used in making ASCII art.
Use in biology
Monospaced fonts are preferable for displaying nucleic acid and protein sequences, as they ensure that the letter representing each nucleotide or amino acid occupies the same amount of space, which enables alignment and visual comparison of different sequences.
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