Variables in c

Variables

A variable is a name of the memory location where data value is stored. That data value may be change during the execution of a program.

Rules for defining variables

• The first letter variable name must be alphabet (uppercase & lowercase), or underscore.
• A variable can combinations of alphabets, digits and underscore.
• In variable name commas or blanks space are not allowed.
• In special symbol only underscore is allowed.
• Keyword not use as variable name.
• Uppercase letter and lower case letters are different. For example Sum is not same as sum or SUM.
• Length should not be more than 8 characters because only first 8 character are treated as significant by many compilers.

Followings are some valid and invalid variable examples

Variable Name	Valid or Invalid	If invalid then reason
Number	Valid
First Number	Invalid	Blank space is not allowed
First_Number	Valid
number	Valid
Number$	Invalid	$ sign not allowed
int	Invalid	Keywords not allowed
int_sum	Valid
1num	Invalid	First letter digit not allowed

 

§  Note that use meaningful variable name in the program.