Tokens in C
Sunny Bhaskar
10/28/20242 min read
In C programming, a token is the smallest unit of a program that is meaningful to the compiler. When a C program is compiled, the compiler breaks the source code into these tokens. There are six types of tokens in C, and they play a crucial role in defining the structure and syntax of the program.
Types of Tokens in C
1. Keywords
These are reserved words in C that have a predefined meaning and purpose. You cannot use them as identifiers (like variable names).
Examples: `int`, `float`, `if`, `else`, `while`, `return`, `void`, `for`, etc.
Example
int main() {
return 0;
}
Here, `int` and `return` are keywords.
2. Identifiers
Identifiers are names given to variables, functions, arrays, and other user-defined entities.
They must begin with a letter (uppercase or lowercase) or an underscore (`_`), followed by letters, digits, or underscores.
Identifiers are case-sensitive in C (e.g., `sum` and `Sum` are different).
Example
int sum, value;
// sum and value are identifiers
3. Constants
Constants are fixed values that do not change during the execution of a program. They can be integer constants, floating-point constants, character constants, or string literals.
Example
int a = 5;
// 5 is an integer constant
float pi = 3.14;
// 3.14 is a floating-point constant
char letter = 'A';
// 'A' is a character constant
4. Operators
Operators are symbols used to perform operations on variables and values. C supports various types of operators like arithmetic, relational, logical, bitwise, assignment, and more.
Example
int x = 5 + 3;
// + is an arithmetic operator
if (x > 3) { // > is a relational operator
// ...
}
5. Special Symbols
These include symbols that have a special meaning in C, such as braces, parentheses, brackets, commas, semicolons, and the pound sign (`#`).
Example
int main()
{
// { and } are special symbols
int arr[5];
// [ and ] are special symbols for arrays
return 0;
// ; is a semicolon that marks the end of a statement
}
6. Strings
Strings are a sequence of characters enclosed in double quotes. Strings are treated as arrays of characters.
Example
char name[] = "Sunny";
// "Sunny" is a string constant
Example Code with Tokens
#include <stdio.h>
// Special Symbol: #, Identifier: stdio.h
int main()
{
// Keywords: int, main, Special Symbols: (), {}
int a = 10;
// Keyword: int, Identifiers: a, Constant: 10
float b = 3.14;
// Keyword: float, Identifier: b, Constant: 3.14
char letter = 'A';
// Keyword: char, Identifier: letter, Constant: 'A'
// Operator: +, Identifier: sum
int sum = a + (int)b;
// Typecasting b from float to int
printf("Sum: %d", sum);
// Special Symbol: (), Identifier: printf, String: "Sum: %d"
return 0;
// Keyword: return, Constant: 0
}
Summary
Tokens are the smallest building blocks of a C program.
The six types of tokens are Keywords, Identifiers, Constants, Operators, Special Symbols, and Strings.
Each token plays a specific role in defining the structure and logic of the program.