Mixing old and new style functions

ANSI C's most sweeping change to the language is the function prototype borrowed from the C++ language. By specifying for each function the number and types of its parameters, not only does every regular compile get the benefits of lint-like argument/parameter checks for each function call, but arguments are automatically converted (just as with an assignment) to the type expected by the function. ANSI C includes rules that govern the mixing of old- and new-style function declarations since there are numerous lines of existing C code that could and should be converted to use prototypes.