<P> In computer programming, a parameter (often called formal parameter or formal argument) is a special kind of variable, used in a subroutine to refer to one of the pieces of data provided as input to the subroutine . These pieces of data are the values of the arguments (often called actual arguments or actual parameters) with which the subroutine is going to be called / invoked . An ordered list of parameters is usually included in the definition of a subroutine, so that, each time the subroutine is called, its arguments for that call are evaluated, and the resulting values can be assigned to the corresponding parameters . </P> <P> Unlike argument in usual mathematical usage, the argument in computer science is thus the actual input expression passed / supplied to a function, procedure, or routine in the invokation / call statement, whereas the parameter is the variable inside the implementation of the subroutine . For example, if one defines the add subroutine as def add (x, y): return x + y, then x, y are parameters, while if this is called as add (2, 3), then 2, 3 are the arguments . Note that variables (and expressions thereof) from the calling context can be arguments: if the subroutine is called as a = 2; b = 3; add (a, b) then the variables a, b are the arguments, not the values 2, 3 . See the Parameters and arguments section for more information . </P>

What is the difference between a parameter and a variable in programming
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