Editing Macro (computer science) (section)

{{Short description|Rule for substituting a set input with a set output}}
{{Redirect|Macro language|ISO macrolanguages|ISO 639 macrolanguage}}
[[File:Jedit macro recorder.png|thumb|250px|[[jEdit|jEdit's]] macro editor]]
In [[computer programming]], a '''macro''' (short for "'''macro instruction'''"; {{ety|el|''μακρο''-|long, large}}<ref>''[[Oxford English Dictionary]]'', ''s.v.'' [https://www.oed.com/view/Entry/111926 macro], [https://www.oed.com/view/Entry/233194 macro-instruction], and [https://www.oed.com/view/Entry/111927 macro-]</ref>) is a rule or [[pattern]] that specifies how a certain input should be [[Map (mathematics)|mapped]] to a replacement output. Applying a macro to an input is known as '''macro expansion'''. 

The input and output may be a sequence of [[lexical token]]s or [[Character (computing)|characters]], or a [[abstract syntax tree|syntax tree]]. Character macros are supported in [[software application]]s to make it easy to invoke common [[Command (computing)|command]] sequences. Token and tree macros are supported in some [[programming language]]s to enable [[code reuse]] or to extend the language, sometimes for [[domain-specific languages]].

Macros are used to make a sequence of computing instructions available to the programmer as a single [[program statement]], making the programming task less tedious and less error-prone.<ref>{{cite journal |last1=Greenwald |first1=Irwin D. |last2=Kane |first2=Maureen |date=April 1959 |title=The Share 709 System: Programming and Modification |journal=Journal of the ACM |location=New York, NY, USA |publisher=ACM |volume=6 |issue=2 |pages=128–133 |doi=10.1145/320964.320967 |s2cid=27424222 |quote=One of the important uses of programmer macros is to save time and clerical-type errors in writing sequence of instructions which are often repeated in the course of a program. |doi-access=free}}</ref><ref>{{cite journal | last = Strachey| first = Christopher | title = A General Purpose Macrogenerator| journal = Computer Journal| volume = 8 | issue = 3 | pages = 225–241|date=October 1965 | doi = 10.1093/comjnl/8.3.225 |author-link=Christopher Strachey| doi-access = free}}</ref> Thus, they are called "macros" because a "big" [[Block (programming)|block of code]] can be expanded from a "small" sequence of characters. Macros often allow positional or keyword parameters that dictate what the [[Conditional assembly language|conditional assembler]] program generates and have been used to create entire [[Computer program|programs]] or program suites according to such variables as [[operating system]], [[Computing platform|platform]] or other factors. The term derives from "macro instruction", and such expansions were originally used in generating [[assembly language]] code.