In C programming language, identifiers are the building blocks of a program. Identifiers are unique names that are assigned to variables, structs, functions, and other entities. They are used to uniquely identify the entity within the program.
RULES FOR NAMING IDENTIFIERS IN C
- We can not use any keyword as an identifier.
- All the identifiers should have a unique name in the same scope.
- Identifiers can not start with a digit.
- The first character of an identifier should always start with an alphabet or underscore, and then it can be followed by any of the characters, digit, or underscore.
- The special characters such as '*','#','@','$' are not allowed within an identifier.
- All the identifiers are case sensitive means the identifiers "hello" and "Hello" will be treated differently. However, both names are identical, but one has a lowercase alphabet, and the other has an uppercase alphabet.
- Length of an identifier should not exceed 31 characters.
- Any blank spaces or commas are not allowed within an identifier.
EXAMPLES OF VALID IDENTIFIERS IN C
- length - It contains only lowercase alphabets.
- total_sum - It contains only '_' as a special character.
- _size - It starts with an underscore '_'.
- len_ - Contains lowercase alphabets and an underscore.
- num1 - Here, the numeric digit comes at the end.
- num_2 - It starts with lowercase and ends with a digit.
EXAMPLES OF INVALID IDENTIFIERS IN C
- 5size (it begins with a digit)
- \@hello (starts with a special character other than '_')
- int ( it is a keyword)
- m n (contains a blank space)
- m+n (contains a special character)
