Tokens in C is the most important element to be used in creating a program in C. We can define the token as the smallest individual element in C. For `example, we cannot create a sentence without using words; similarly, we cannot create a program in C without using tokens in C. Therefore, we can say that tokens in C is the building block or the basic component for creating a program in C language.

Classification of tokens in C

C Supports 6 Types of Tokens

  1. Keywords
  2. Identifiers
  3. Strings
  4. Operators
  5. Constants
  6. Special Characters

1. Keywords

Keywords in C language are predefined or reserved keywords used to expose the behavior of the data. There are 32 keywords in C. Each keyword has its functionality to do.


2. Identifier

Identifier in C language is used for naming functions, variables, structures, unions, arrays, etc. The identifier is user-defined words. These identifiers can be composed of uppercase, lowercase letters, digits, underscore. Identifiers never used for keywords. Rules to construct identifiers is below

  • The first character should be either alphabet or underscore and then followed by any character, digit.
  • Identifiers are case sensitive as there is Aand a treated as different.
  • Commas and blank space are not allowed
  • Keywords can’t be used for identifiers.
  • The length of the identifiers should not be more than 31 characters.
  • Naming convention should understandable to the user.

3. Strings

Strings in C is an array of characters having null character ‘\0’ at the end of the string. Strings in C are enclosed in double-quotes(“”) and Characters are enclosed in single quotes(”).


char a[10]={'1','2','3'};
char a[]="Amardeep";
char a[10]="Paramesh";

4. Operators

This is used to perform special operations on data.

Unary Operator: A unary operator is an operator applied to the single operand. For example: increment operator (++), decrement operator (--), sizeof, (type)*.

Binary Operator: The binary operator is an operator applied between two operands. The following is the list of the binary operators:

  • Arithmetic Operators
  • Relational Operators
  • Shift Operators
  • Logical Operators
  • Bitwise Operators
  • Conditional Operators
  • Assignment Operator
  • Misc Operator

5. Constants in C

A constant is a value assigned to the variable which will remain the same throughout the program, i.e., the constant value cannot be changed.

There are two ways of declaring constant:

  • Using const keyword
  • Using #define pre-processor

Types of constants in C

6. Special Characters in C

Some special characters are used in C, and they have a special meaning which cannot be used for another purpose.

  • Square brackets [ ]: The opening and closing brackets represent the single and multidimensional subscripts.
  • Simple brackets ( ): It is used in function declaration and function calling. For example, printf() is a pre-defined function.
  • Curly braces { }: It is used in the opening and closing of the code. It is used in the opening and closing of the loops.
  • Comma (,): It is used for separating for more than one statement and for example, separating function parameters in a function call, separating the variable when printing the value of more than one variable using a single printf statement.
  • Hash/pre-processor (#): It is used for pre-processor directive. It basically denotes that we are using the header file.
  • Asterisk (*): This symbol is used to represent pointers and also used as an operator for multiplication.
  • Tilde (~): It is used as a destructor to free memory.
  • Period (.): It is used to access a member of a structure or a union.