Functions can return any type except an array or a function type. If no type is included, the default is 'int'. Functions that return nothing have a return type of void. One can consider the declaration of the return type as a description of one of the mechanisms a function has to communicate with the rest of the program. Each element of the parameter list is declared using a format similar to that used in variable and constant declarations.
Commas separate the elements of the list and a semicolon appears after the closing parenthesis.
Such parameters are called reference parameters . Arrays types do not need this symbol. Such default declarations must come at the end of the parameter list. In order for a function to be used, it must be called by another function. The parameters included in function declarations are called formal parameters while the parameters listed in a function call are called the actual parameters .