Ivor Horton's Beginning Visual C++ 2012

UNDERSTANDING FUNCTIONS

Up to now, you haven’t really been able to structure your program code in a modular fashion, because you only know how to construct a program as a single function, main(); but you have been using library functions of various kinds as well as functions belonging to objects. Whenever you write a C++ program, you should have a modular structure in mind from the outset, and as you’ll see, a good understanding of how to implement functions is essential to object-oriented programming.

There’s quite a lot to structuring your C++ programs, so to avoid indigestion, you won’t try to swallow the whole thing in one gulp. After you have chewed over and gotten the full flavor of these morsels, you move on to the next chapter, where you get further into the meat of the topic.

First, I’ll explain the broad principles of how a function works. A function is a self-contained block of code with a specific purpose. A function has a name that both identifies it and is used to call it for execution in a program. The name of a function is global if it is not defined within a namespace, otherwise the name is qualified by the namespace name. The name of a function is not necessarily unique, as you’ll see in the next chapter; however, functions that perform different actions should generally have different names.

The name of a function is governed by the same rules as those for a variable. A function name is, therefore, a sequence of letters and digits, the first of which is a letter, ...