In this tutorial, you are going to learn about Keywords and Identifiers in C Programming.
Introduction to Tokens
A sentence without words is impossible. Similarly a program in C is impossible to create without tokens. It is the smallest individual unit of a program which is meaningful to the compiler. Token is the building block or the basic component for creating a program in C. It is also known as Lexical Issue.
Tokens in C can be classified as follows: Keywords, Identifiers, Strings, Operators, Constant and Special Characters.
Keywords
- Predefined set of words which have special meaning within the compiler.
- Each keyword has its own functionality and they cannot be used as variable names.
- If the keywords are used as the variable names, it means that we are assigning a different meaning to the keyword which is not permitted.
- C language supports 32 keywords which are stated below:
Example: double a, b, c; Here double is a data type and is a keyword.
Supported Keywords in C
| int | double | auto | struct |
| break | else | long | switch |
| case | enum | register | typedef |
| char | extern | return | union |
| const | float | short | unsigned |
| continue | for | signed | void |
| default | goto | sizeof | volatile |
| do | if | static | while |
Identifiers
- Used for Naming variables, functions and arrays.
- These are user defined words composed of uppercase, lowercase letters, underscore, or digits but the starting letter should either be an underscore or an alphabet.
- Identifiers cannot be used as keywords.
Naming Rules of Identifiers
- The first character of an identifier should either be an alphabet or an underscore sign (_). The next characters can either be a digit, a character or underscore.
- There should not be any space between variable names.
- It should not begin with any numerical digit.
- Identifiers are case-sensitive as it distinguishes between uppercase and lower case letters.
- Commas or blank spaces cannot be specified within an identifier.
- An identifier cannot be a keyword.
Example:
void main()
{
int a=5;
}
Here main and a are identifiers.
This post is written by Divyanshu Shekhar (BTech CS, Chandigarh Engineering College). If you like TheCode11, then do follow us on Facebook, Twitter and Instagram.
