Constant

Constant

Constant is an entity that does not change during program execution. Example when we write number=10 than 10 is constant in all program and never change value.
There are mainly two types constants:
1.    Primary constants
       i)Integer constant
       ii)Real Constant
       iii)character Constant


2.    Secondary Constants
       i)Array
      ii)Structure
      iii)Pointer
       iv)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..

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