The function is executed only when it is called. If it's never called, it's never executed. The block of code can be executed as many times as desired, by calling it many times. A function is executed by calling it. Its executable statements are executed Its local variables are destroyed Any return value is returned to the calling function.
Function calls can appear anywhere any other expression can appear.
The parameters have the value of the argument that is in the function call. Prototypes Like variables, functions must be defined before they are used. Prototypes define the function call interface. Prototypes mirror the function definition, without function body.