Editing Parameter (computer programming) (section)

{{Short description|Representation of an argument in a function definition}}
{{Other uses|Parameter (disambiguation)}}
In [[computer programming]], a '''parameter''', a.k.a.  '''formal argument''', is a [[Variable (computer science)|variable]] that represents an argument, a.k.a. actual argument, a.k.a. actual parameter, to a [[subroutine]] call.{{efn|1=In this article, the term "subroutine" refers to any subroutine-like construct, which have different names and slightly different meanings depending on the [[programming language]] being discussed.}}.<ref name="Oracle">{{cite web | title=Passing Information to a Method or a Constructor (Learning the Java Language > Classes and Objects) | website=The Java™ Tutorials | url=https://docs.oracle.com/javase/tutorial/java/javaOO/arguments.html | access-date=2021-09-09 | quote=Parameters refers to the list of variables in a method declaration. Arguments are the actual values that are passed in when the method is invoked. When you invoke a method, the arguments used must match the declaration's parameters in type and order.}}</ref><ref>{{cite book|last1=Prata|first1=Stephen|title=C primer plus|date=2004|publisher=Sams|isbn=978-0-672-32696-7|pages=276–277|edition=5th}}</ref><ref>{{cite web|title=Working Draft, Standard for Programming Language C++|url=http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2005/n1905.pdf|archive-url=https://web.archive.org/web/20051214034042/http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2005/n1905.pdf|url-status=dead|archive-date=December 14, 2005|website=Open Standards |date=2005-10-19 |access-date=1 January 2018}}</ref><ref>{{cite web|last1=Gordon|first1=Aaron|title=Subprograms and Parameter Passing|url=http://rowdysites.msudenver.edu/~gordona/cs3210/lects/lect10.html|website=rowdysites.msudenver.edu/~gordona|access-date=1 January 2018|archive-url=https://web.archive.org/web/20180101140104/http://rowdysites.msudenver.edu/~gordona/cs3210/lects/lect10.html|archive-date=1 January 2018|url-status=dead}}</ref> A function's [[function signature|signature]] defines its parameters. A call invocation involves evaluating each argument expression of a call and associating the result with the corresponding parameter.

For example, consider subroutine <code>def add(x, y): return x + y</code>. Variables <code>x</code> and <code>y</code> are parameters. For call <code>add(2, 3)</code>, the expressions <code>2</code> and <code>3</code> are arguments. For call <code>add(a+1, b+2)</code>, the arguments are <code>a+1</code> and <code>b+2</code>.

Parameter passing is defined by a programming language. [[Evaluation strategy]] defines the semantics for how parameters can be declared and how arguments are passed to a subroutine. Generally, with [[call by value]], a parameter acts like a new, local variable initialized to the value of the argument. If the argument is a variable, the subroutine cannot modify the argument state because the parameter is a copy. With [[call by reference]], which requires the argument to be a variable, the parameter is an alias of the argument.