IDENTIFIERS

Identifiers are the names that are to be given to the variables, functions, data types and labels in a program. the names  of a variable can consist of alphabets (letters)and numbers. Other characters are not allowed in the name of variable.An underscore character can be used as a valid character in the variable name.The variable name starts with an alphabet and its length may vary from one character to 32 characters.The first character in a variable's name should be an alphabet. ie..,a number is not allowed as a first character in the variable name.The valid variable names are:
             
                 x
                 length
                 x_value
                 y_value
                 a123

Keywords (which have special meaning in C) cannot be used as identifiers.