C Language Operators

1. What is an Operator?

An expression is a combination of operators and operands that is evaluated to produce a result.

Example

2 + 3
        

• 2 + 3 → Expression
• + → Operator
• 2 and 3 → Operands

Examples of Expressions

2. Types of Operators Based on Number of Operands

3. Types of C Operators Based on Operation

4. Arithmetic Operators

Arithmetic operators are used to perform basic mathematical operations.

Example Program

#include <stdio.h>

int main()
{
    int res;

    res = 5 + 2;
    printf("Result = %d\n", res);

    res = 5 - 2;
    printf("Result = %d\n", res);

    res = 5 * 2;
    printf("Result = %d\n", res);

    res = 5 / 2;
    printf("Result = %d\n", res);

    res = 5 % 2;
    printf("Result = %d\n", res);

    return 0;
}
        

Output

5. Assignment Operator

Syntax

variable = value;
variable = expression;
variable = another_variable;
        

Example

#include <stdio.h>

int main()
{
    int a, b;

    a = 12;
    b = 24;

    printf("a = %d\n", a);
    printf("b = %d\n", b);

    a = b;

    printf("After a = b:\n");
    printf("a = %d\n", a);
    printf("b = %d\n", b);

    return 0;
}
        

6. Swapping Two Variables

Swapping means exchanging the values of two variables.

Using a Temporary Variable

#include <stdio.h>

int main()
{
    int x, y, temp;

    x = 12;
    y = 24;

    printf("Before swapping:\n");
    printf("x = %d\n", x);
    printf("y = %d\n", y);

    temp = x;
    x = y;
    y = temp;

    printf("\nAfter swapping:\n");
    printf("x = %d\n", x);
    printf("y = %d\n", y);

    return 0;
}
        

7. Short-Hand / Compound Assignment Operators

Compound assignment operators provide a shorter way of writing an expression where the same variable appears on both sides of an assignment.

Example

#include <stdio.h>

int main()
{
    int x = 10;
    int y = 20;

    printf("x = %d\n", x);

    x += 2;
    printf("After x += 2, x = %d\n", x);

    x += y;
    printf("After x += y, x = %d\n", x);

    y += x;
    printf("After y += x, y = %d\n", y);

    return 0;
}
        

8. Type Conversion and Type Casting

Type conversion occurs when a value of one data type is converted into another data type.

Implicit Type Conversion

When the compiler automatically converts one data type into another, it is called implicit type conversion.

int a = 10;
float b;

b = a;
        

Here, the integer value 10 is automatically converted to a floating-point value.

Explicit Type Conversion / Type Casting

When the programmer explicitly specifies the required data type, it is called type casting.

float x;

x = (float)'a';

printf("%f", x);
        

Example: Integer Division vs Type Casting

#include <stdio.h>

int main()
{
    int a = 5;
    int b = 2;

    printf("Integer division = %d\n", a / b);
    printf("Floating division = %.2f\n", (float)a / b);

    return 0;
}
        

9. Type Conversion Practice

10. Increment and Decrement Operators

Increment

x++ or ++x increases the value of x by 1.

Conceptually:

x = x + 1;
        

Decrement

x-- or --x decreases the value of x by 1.

x = x - 1;
        

Example

#include <stdio.h>

int main()
{
    int x = 10;

    printf("x = %d\n", x);

    x++;
    printf("After increment, x = %d\n", x);

    x--;
    printf("After decrement, x = %d\n", x);

    return 0;
}
        

11. Pre-Increment and Post-Increment

Post-Increment Example

#include <stdio.h>

int main()
{
    int a = 2;

    printf("a = %d\n", a++);
    printf("a = %d\n", a);

    return 0;
}
        

In a++, the old value is used first and then a is increased.

Another Example

#include <stdio.h>

int main()
{
    int x = 10;
    int y;

    y = x++ + 5;

    printf("x = %d\n", x);
    printf("y = %d\n", y);

    return 0;
}
        

Pre-Increment Example

int x = 10;
int y;

y = ++x + 5;
        

Here x becomes 11 first, so y becomes 16.

12. Relational / Comparison Operators

Relational operators are used to compare two values. The result of a comparison is either true or false.

In C, a true condition generally evaluates to 1, while a false condition evaluates to 0.

Example Program

#include <stdio.h>

int main()
{
    int res;

    res = 5 > 7;
    printf("5 > 7 = %d\n", res);

    res = 5 >= 7;
    printf("5 >= 7 = %d\n", res);

    res = 5 < 7;
    printf("5 < 7 = %d\n", res);

    res = 5 <= 7;
    printf("5 <= 7 = %d\n", res);

    res = 5 == 7;
    printf("5 == 7 = %d\n", res);

    res = 5 != 7;
    printf("5 != 7 = %d\n", res);

    return 0;
}
        

13. Logical / Boolean Operators

Logical operators are used to combine or modify conditions. Their result is either 1 (true) or 0 (false).

Truth Table

Example Program

#include <stdio.h>

int main()
{
    int res;

    res = (5 > 7) && (12 < 20);
    printf("AND result = %d\n", res);

    res = (5 > 7) || (12 < 20);
    printf("OR result = %d\n", res);

    res = !(5 > 7);
    printf("NOT result = %d\n", res);

    return 0;
}
        

14. Bitwise Operators

Bitwise operators work directly with the individual bits of integer values.

Example: Bitwise AND

4 = 0100
5 = 0101
    ----
4 & 5 = 0100 = 4
        

Example Program

#include <stdio.h>

int main()
{
    int res;

    res = 4 & 5;
    printf("4 & 5 = %d\n", res);

    res = 4 << 2;
    printf("4 << 2 = %d\n", res);

    return 0;
}
        

Bitwise AND Example

  4 = 0100
  5 = 0101
      ----
4 & 5 = 0100
        = 4
        

Bitwise OR Example

  4 = 0100
  5 = 0101
      ----
4 | 5 = 0101
        = 5
        

Bitwise XOR Example

  4 = 0100
  5 = 0101
      ----
4 ^ 5 = 0001
        = 1
        

Left Shift

4 = 0100

4 << 1 = 1000 = 8
4 << 2 = 10000 = 16
        

15. Quick Revision Table

16. Practice Questions

Level 1 – Basic

Level 2 – Predict the Output

int x = 10;
printf("%d", x++);
            

int x = 10;
printf("%d", ++x);
            

int x = 5;
int y;

y = x++ + 10;
            

int x = 5;
int y = 2;

printf("%d", x / y);
printf("%d", x % y);
            

printf("%d", 4 & 5);
            

Level 3 – Write Programs

17. Challenge Questions

int a = 5;
int b = 10;

a += b;
b += a;

printf("a = %d\n", a);
printf("b = %d\n", b);
            

int a = 10;
int b = 20;

a++;
++b;

a += b;
b -= 5;
            

int a = 4;
int b = 5;

printf("%d\n", a & b);
printf("%d\n", a | b);
printf("%d\n", a ^ b);
            

printf("%d\n", 5 / 2);
printf("%.1f\n", (float)5 / 2);
            

18. Important Points to Remember

• = is assignment; == is comparison.
• 5 / 2 gives 2 when both operands are integers.
• 5 % 2 gives the remainder 1.
• Post-increment uses the old value before incrementing.
• Pre-increment increments the value before it is used.
• Zero represents false in a logical context.
• Any non-zero value represents true in a logical context.
• Relational operators produce 0 or 1 in C.
• Bitwise operators work on individual bits of integer values.
• Type casting can be used to explicitly convert a value to another type.