IDENTIFIERS IN C

IDENTIFIERS:

Identifiers are the names given to the variables, functions, data types and labels in a program. They are user-defined names, consisting of alphabets (letters) and numbers. Other characters are not allowed in the name of a 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

Lower case letters are generally preferred.  However, upper case letters are also permitted.

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

The following variable names are invalid and the reasons are stated.

·        123 - The first character is a number

·        1abc - The first character is a number

·        x value - A blank character is used

·        x&y - A character other than alphabet and number is used & is not a valid character in a variable name.

·        for - It is a keyword