Parameter (computer programming)

In computer programming, a parameter, a.k.a. formal argument, is a variable that represents an argument, a.k.a. actual argument, a.k.a. actual parameter, to a subroutine call.^[a].^[1][2][3][4] A function's 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 def add(x, y): return x + y. Variables x and y are parameters. For call add(2, 3), the expressions 2 and 3 are arguments. For call add(a+1, b+2), the arguments are a+1 and b+2.

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.

Cite error: There are <ref group=lower-alpha> tags or {{efn}} templates on this page, but the references will not show without a {{reflist|group=lower-alpha}} template or {{notelist}} template (see the help page).