Practical C Programming, 3rd Edition

Chapter 9. Variable Scope and Functions

But in the gross and scope of my opinion

This bodes some strange eruption to our state.

—Shakespeare [Hamlet, Act 1, Scene 1]

So far, we have been using only global variables. In this chapter, we will learn about other kinds of variables and how to use them. This chapter also tells you how to divide your code into functions.

Scope and Class

All variables have two attributes: scope and class. The scope of a variable is the area of the program in which the variable is valid. A global variable is valid everywhere (hence the name global), so its scope is the whole program. A local variable has a scope that is limited to the block in which it is declared and cannot be accessed outside that block. A block is a section of code enclosed in curly braces ({}). Figure 9-1 shows the difference between local and global variables.

Figure 9-1. Local and global variables

You can declare a local variable with the same name as a global variable. Normally, the scope of the variable count (first declaration) would be the whole program. The declaration of a second local count takes precedence over the global declaration inside the small block in which the local count is declared. In this block, the global count is hidden. You can also nest local declarations and hide local variables. Figure 9-2 illustrates a hidden variable.

Figure 9-2. Hidden variables

The variable count ...