Constants & Variables

1 Constants

 

Constants in C are fixed value that does not change during the execution of a program. Constants can be of any of the basic data types.  There are basic two types of Constants:

1)    Primary Constants.

2)    Secondary Constants

In Primary constants we have three types of constants:

a)     Integer constants

b)    Real constants

c)     Character constants.

In Secondary constants we have various constants like Arrays, Pointer, structure, union and enum etc.

Rules for constructing Integer constants

1)    An integer constant must have atleast one digit.

2)    It must not have a decimal point.

3)    It can be either positive or negative.

4)    Default sign is positive.

5)    The allowable range is -32768 to 32767

6)    No commas or blanks are allowed.

For ex: 426, +782 ,-8000.

 Rules for constructing Real constants

1)    An real constant must have atleast one digit

2)    It must have a decimal point.

3)    It can be either positive or negative.

4)    Default sign is positive.

5)    No commas or blanks are allowed.

For ex: +325.34, -32.76, 426.0

 

Rules for constructing Character constants

1)    A character constant is a single alphabet, a single digit or a single special symbol enclosed within single inverted commas.

Ex: ‘ A’, ‘1’, ‘=’.

2)    Maximum length can be 1 character.