A constant is a number, character, or character string that can be used as a value in a program. Use constants to represent floating-point, integer, enumeration, or character values that cannot be modified.

constant:
 floating-point-constant
 integer-constant
 enumeration-constant
 character-constant

Constants are characterized by having a value and a type. Floating-point, integer, and character constants are discussed in the next three sections. Enumeration constants are described in Enumeration Declarations.

Elements of C