C++ Primer Plus

User-Defined Functions

The standard C library provides more than 140 predefined functions. If one fits your needs, by all means use it. But often you have to write your own, particularly when you design classes. Anyway, it’s fun to design your own functions, so now let’s examine that process. You’ve already used several user-defined functions, and they have all been named main(). Every C++ program must have a main() function, which the user must define. Suppose you want to add a second user-defined function. Just as with a library function, you can call a user-defined function by using its name. And, as with a library function, you must provide a function prototype before using the function, which you typically do by placing the prototype above ...