C++ How to Program, 10/e

E.3 #define Preprocessing Directive: Symbolic Constants

The #define preprocessing directive creates symbolic constants—constants represented as symbols—and macros—operations defined as symbols. The #define preprocessing directive format is

• #define identifier replacement-text

When this line appears in a file, all subsequent occurrences (except those inside a string) of identifier in that file will be replaced by replacement-text before the program is compiled. For example,

#define PI 3.14159

replaces all subsequent occurrences of the symbolic constant PI with the numeric constant 3.14159. Symbolic constants enable you to create a name for a constant and use the name throughout the program. Later, if the constant needs to be modified throughout ...