Constant

1.  Constant is an entity that does not change during program execution.    

Example: int i=10;  

                  when we write this i=10 then i is constant in all program and never change value until we give any other value for i. 

 

There are mainly two types constants:

1. Primary constants
   • Integer constant
   • Real Constant
   • character Constant
2. Secondary Constants
   • Array
   • Structure
   • Pointer
   • Union

Rules for construction Integer Constant

• At least one digit must have an integer constant
• It can be positive or negative. The general range of integer constant is -32768 to +32767.(NOTE : Normally range depend on compiler.)
• No commas or blank spaces are allowed within integer constant.
• Integer constant must not having decimal point.
• Example of integer constant are as 364,-66,+786,-1

Rules for constructing Floating point or Real constant

• At least one digit must have an real constant.
• Real constant must have decimal point.
• It may be positive or negative.
• No commas or blank spaces are allowed within real constant.
• Example of real point constant : +23.0, 786.786, -0.786, 0.0

 Rules for constructing Character constant

• Any single entity(like as single alphabet, single digit or single symbol) are enclosed within single inverted commas, are called character constant.
• Example of Character constant : 'a', 'A', '*', '4' etc..