Variables in C

 A variable is data name that may be used to store a data value; a variable may take different values at different times during execution

1.       Variable name may consist of letters, digits and the underscore (_) characters.

2.       The first character in variable name must be an alphabet or underscore (_).

3.       Some 'C' compilers allow variables names whose length could be up to 40 characters; however the length should be normally more than eight characters.

4.       Only lower case letters are significant to use.

5.       Variable should not be a keyword

6.       No commas or blank space and symbols are allowed within variable name.

7.       If we want to initialize the variable, then we can use (=) symbol in front of the variable name and assign the value

Examples:        
                Student                      auto
                resultl23                    include
                roll_mark                   5type
                mm mark                   stud mark
                (valid)                         (invalid)