Constants:

A Constant is a quantity whose value cannot be changed ,it cannot be changed like a Variable. There are Numeric Constants and String Constants.

Numeric Constant:

                Numeric Constant consists of integers, single-precision or double- precision numbers.

String Constant:

                A String Constant  is a sequence of alphanumeric characters enclosed in double quotation marks. The maximum length of a String Constant is 255 characters.