C Constants
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.
Syntax
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.