C++ improvements over C
Programming in C++ language - Concepts

The C language is lax when it comes to declaring functions. Indeed, while it allows complete declarations (prototype with type of arguments and return value), it also authorizes partial declarations, and in some cases even no declaration at all.

C++ retains only the most reliable aspect of C, as it was already used by C programmers anxious to secure their programs. It requires any function used in a source file to be :

• or a declaration in the form of a prototype (specifying the function name, the type of any arguments and the type of return value), as in this example...