Function definition
type function_name(parameter list) {body}
semantic:
The type of a function depends on the value that a function returns ,if any. Parameter list are syntactically a comma-separated list, with each item a type declaration followed by an identifier (formal parameters). Upon function invocation, the value of the argument (actual parameter) corresponding to a formal parameter is used within the body of the executing function. (Call-By-Value/Call-By-Reference)