C++ Primer Plus

Use const Instead of #define to Define Constants

Symbolic constants make code more readable and maintainable. The constant’s name indicates its meaning, and if you need to change the value, you just have to change the value once, in the definition, and then recompile. C uses the preprocessor to create symbolic names for a constant:

#define MAX_LENGTH 100

The preprocessor then does a text substitution in your source code, replacing occurrences of MAX_LENGTH with 100 prior to compilation.

The C++ approach is to apply the const modifier to a variable declaration:

const int MAX_LENGTH = 100;

This treats MAX_LENGTH as a read-only int.

There are several advantages to using the const approach. First, the declaration explicitly names the type. With ...