C Programming - C Tokens

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C Programming - C Tokens

In the C programming language, a token is the smallest unit of a program. The compiler identifies tokens during the compilation process to understand the program structure.

Types of Tokens in C

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

1. Keywords

• Reserved words with a predefined meaning in C.
• Cannot be used as identifiers (e.g., variable names or function names).
• Examples: :

 int, float, if, else, while, return, break, void, char 

• Example in Code:

  int number = 10;  // 'int' is a keyword  

2. Identifiers

• Names given to variables, functions, arrays, etc., defined by the programmer.
• Must begin with a letter or an underscore (_) and can be followed by letters, digits, or underscores.
• Case-sensitive.
• Rules:
• Cannot be a keyword.
• Should not contain spaces or special symbols (except _).
• Must be unique within its scope.
• Example in Code:

  int age = 25;  // 'age' is an identifier 

3. Constants

• Fixed values that do not change during program execution.
• Types:
• Integer Constants: Whole numbers (e.g., 10, -45).
• Floating-point Constants: Decimal numbers (e.g., 3.14, -0.99).
• Character Constants: A single character enclosed in single quotes (e.g., 'A').
• String Constants: A sequence of characters enclosed in double quotes (e.g., "Hello").
• Example in Code:

 const float PI = 3.14;  // 'PI' is a constant 

4. Strings

• A sequence of characters enclosed in double quotes.
• Represented as an array of characters internally.
• Example in Code:

 char greeting[] = "Hello, World!"; 

5. Operators

• Symbols used to perform operations on variables and values.
• Types:
• Arithmetic Operators: +, -, *, /, %
• Relational Operators: ==, !=, <, >, <=, >=
• Logical Operators: &&, ||, !
• Assignment Operators: =, +=, -=, *=, /=
• Bitwise Operators: &, |, ^, ~, <<, >>
• Example in Code:

 int sum = a + b;  // '+' is an arithmetic operator 

6. Special Symbols

• Special characters used in C for specific purposes.
• Examples:
• Braces {}: Define blocks of code.
• Parentheses (): Enclose function arguments or expressions.
• Brackets []: Enclose array elements.
• Comma ,: Separate multiple variables or parameters.
• Semicolon ;: End statements.
• Pound sign #: Preprocessor directives.
• Asterisk *: Pointer declaration or multiplication.
• Example in Code:

 int arr[5] = {1, 2, 3, 4, 5};  // '{}' and '[]' are special symbols 

Code Example with All Tokens

 


#include <stdio.h>  // Preprocessor directive
 
int main() {  // 'int' is a keyword, 'main' is an identifier
    int num = 10;  // 'int' is a keyword, 'num' is an identifier, '10' is a constant
    float pi = 3.14;  // 'float' is a keyword, 'pi' is an identifier, '3.14' is a constant
    char c = 'A';  // 'char' is a keyword, 'c' is an identifier, 'A' is a character constant
   
    printf("Number: %d\n", num);  // 'printf' is a function, "Number: %d" is a string
    return 0;  // 'return' is a keyword, '0' is a constant
}
 

Summary of Tokens

These tokens form the building blocks of any C program. Understanding them is crucial for writing and interpreting C code effectively.