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Computer programming

In computer programming, two notions of parameter are commonly used, and are referred to as parameters and arguments —or more formally as a formal parameter and an actual parameter.

For example, in the definition of a function such as

x is the formal parameter (the parameter) of the defined function.

When the function is evaluated for a given value, as in

3 is the actual parameter (the argument) for evaluation by the defined function; it is a given value (actual value) that is substituted for the formal parameter of the defined function. (In casual usage the terms parameter and argument might inadvertently be interchanged, and thereby used incorrectly.)

These concepts are discussed in a more precise way in functional programming and its foundational disciplines, lambda calculus and combinatory logic. Terminology varies between languages; some computer languages such as C define parameter and argument as given here, while Eiffel uses an alternative convention.