The function must be declared to have the same type as this value. If the function does not return a value then it must be given the type void .
Information is passed into a function via the parameter-list .
Each parameter must be given a type. If not declared to be otherwise then parameters are treated as value parameters If a parameter is a value parameter then the function operates on a copy of the value of the actual parameter hence the value of the actual parameter cannot be changed by the function. A function prototype provides information to the compiler about the return type of a function and the types of its parameters. The function prototype must appear in the program before the function is used. Any variable declared inside a function is local to that function and has existence and meaning only inside the function.