__FORCETOC__ In the written form of many

language Language is a structured system of communication. The structure of a language is its grammar and the free components are its vocabulary. Languages are the primary means by which humans communicate, and may be conveyed through a variety of met ...

s, an indentation or indent is an empty space at the beginning of a line to signal the start of a new

paragraph A paragraph () is a self-contained unit of discourse in writing dealing with a particular point or idea. Though not required by the orthographic conventions of any language with a writing system, paragraphs are a conventional means of organizing e ...

. Many

computer languages A computer language is a formal language used to communicate with a computer. Types of computer languages include: * Construction language – all forms of communication by which a human can specify an executable problem solution to a comput ...

have adopted this technique to designate "paragraphs" or other logical blocks in the program. For example, the following lines are indented, using between one and six

spaces Spaces may refer to: * Google Spaces (app), a cross-platform application for group messaging and sharing * Windows Live Spaces, the next generation of MSN Spaces * Spaces (software), a virtual desktop manager implemented in Mac OS X Leopard * Spac ...

: This paragraph is indented by 1 space. This paragraph is indented by 3 spaces. This paragraph is indented by 6 spaces. In computer programming, the

neologism A neologism Greek νέο- ''néo''(="new") and λόγος /''lógos'' meaning "speech, utterance"] is a relatively recent or isolated term, word, or phrase that may be in the process of entering common use, but that has not been fully accepted int ...

s outdent, unindent and dedent are used to describe the reversal of the indentation process, realigning text with the page margin (or with previous, lesser, levels of indentation). In

right-to-left In a script (commonly shortened to right to left or abbreviated RTL, RL-TB or R2L), writing starts from the right of the page and continues to the left, proceeding from top to bottom for new lines. Arabic, Hebrew, Persian, Pashto, Urdu, Kashmiri ...

languages (e.g.

Hebrew Hebrew (; ; ) is a Northwest Semitic language of the Afroasiatic language family. Historically, it is one of the spoken languages of the Israelites and their longest-surviving descendants, the Jews and Samaritans. It was largely preserved ...

and

Arabic Arabic (, ' ; , ' or ) is a Semitic languages, Semitic language spoken primarily across the Arab world.Semitic languages: an international handbook / edited by Stefan Weninger; in collaboration with Geoffrey Khan, Michael P. Streck, Janet C ...

), indentation is used just the same, but from the right margin of the paper, where the line begins.

Indentation in typesetting

There are three main types of indentation, illustrated below in relation to borders representing the page dimensions.

Indentation in programming

In computer

programming language A programming language is a system of notation for writing computer programs. Most programming languages are text-based formal languages, but they may also be graphical. They are a kind of computer language. The description of a programming ...

s, indentation is used to format program

source code In computing, source code, or simply code, is any collection of code, with or without comments, written using a human-readable programming language, usually as plain text. The source code of a program is specially designed to facilitate the wo ...

to improve readability. Indentation is generally only of use to programmers;

compiler In computing, a compiler is a computer program that translates computer code written in one programming language (the ''source'' language) into another language (the ''target'' language). The name "compiler" is primarily used for programs that ...

s and

interpreters Interpreting is a translational activity in which one produces a first and final target-language output on the basis of a one-time exposure to an expression in a source language. The most common two modes of interpreting are simultaneous inter ...

rarely care how much

whitespace White space or whitespace may refer to: Technology * Whitespace characters, characters in computing that represent horizontal or vertical space * White spaces (radio), allocated but locally unused radio frequencies * TV White Space Database, a mec ...

is present in between programming statements. However, certain programming languages rely on the use of indentation to demarcate programming structure, often using a variation of the

off-side rule A computer programming language is said to adhere to the off-side rule of syntax if blocks in that language are expressed by their indentation. The term was coined by Peter Landin, possibly as a pun on the offside rule in association football. ...

. The

Haskell Haskell () is a general-purpose, statically-typed, purely functional programming language with type inference and lazy evaluation. Designed for teaching, research and industrial applications, Haskell has pioneered a number of programming lang ...

, Occam,

Python Python may refer to: Snakes * Pythonidae, a family of nonvenomous snakes found in Africa, Asia, and Australia ** ''Python'' (genus), a genus of Pythonidae found in Africa and Asia * Python (mythology), a mythical serpent Computing * Python (pro ...

MoonScript Lua ( ; from meaning ''moon'') is a lightweight, high-level, multi-paradigm programming language designed primarily for embedded use in applications. Lua is cross-platform, since the interpreter of compiled bytecode is written in ANSI C, an ...

, and Ya programming languages rely on indentation in this way. Opinions about where to indent, whether to use spaces or tabs, and how many spaces to use are often hotly debated among programmers, leading some to describe indentation disputes as akin to a

religious war A religious war or a war of religion, sometimes also known as a holy war ( la, sanctum bellum), is a war which is primarily caused or justified by differences in religion. In the modern period, there are frequent debates over the extent to wh ...

. In 2006 a third method of indentation was proposed, called

elastic tabstops A tab stop on a typewriter is a location where the carriage movement is halted by an adjustable end stop. Tab stops are set manually, and pressing the tab key causes the carriage to go to the next tab stop. In text editors on a computer, the same ...

. In addition to general indentation of statements, different bracket indentation styles are commonly used.

References

{{Commons cat, Indentation (typesetting) Typography Source code