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Loosely, a parameter is a type, and an argument is an instance. A parameter is an intrinsic property of the procedure, included in its definition. For example, in many languages, a procedure to add two supplied integers together and calculate the sum would need two parameters, one for each integer.
With named parameters, it is usually possible to provide the arguments in any order, since the parameter name attached to each argument identifies its purpose. This reduces the connascence between parts of the program. A few languages support named parameters but still require the arguments to be provided in a specific order.
Some programming languages almost always use curried functions to achieve multiple arguments; notable examples are ML and Haskell, where in both cases all functions have exactly one argument. This property is inherited from lambda calculus , where multi-argument functions are usually represented in curried form.
A copy of the argument is passed in and the value computed during the call is copied to the argument on return: Algol, Swift in-out parameters by name: Like a macro – replace the parameters with the unevaluated argument expressions, then evaluate the argument in the context of the caller every time that the callable uses the parameter: Algol ...
A free variable is a notation (symbol) that specifies places in an expression where substitution may take place and is not a parameter of this or any container expression. The idea is related to a placeholder (a symbol that will later be replaced by some value), or a wildcard character that stands for an unspecified symbol.
^c In Fortran, function/subroutine parameters are called arguments (since PARAMETER is a language keyword); the CALL keyword is required for subroutines. ^d Instead of using "foo" , a string variable may be used instead containing the same value.
This article makes a big deal about the distinction between the terms argument vs. parameter, but I asked several career programmers and computer scientists, and none are used to making this distinction in practice, and in looking at a variety of programming and computer science books, the names argument and parameter are often used ...
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 y = f(x) = x + 2, x is the formal parameter (the parameter) of the defined function.