Bitwise Operators & Bit Manipulation in C

This document covers Bitwise Operators & Bit Manipulation in C.

Bitwise operators in C allow manipulation of individual bits within data types. They are used in low-level programming, memory optimization, encryption, and embedded systems.

In this section, we will cover:

• Bitwise AND (&), OR (|), XOR (^), NOT (~).
• Left Shift (<<) and Right Shift (>>).
• Bit Masks (Setting, Clearing, and Toggling Bits).
• Practical Use Cases in Optimization and Low-Level Programming.

Bitwise Operators in C

Overview of Bitwise Operators

Overview of Bitwise Operators

Operator	Symbol	Description	Example (a = 5, b = 3)
Bitwise AND	&	Performs AND on each bit	5 & 3 = 1 (0101 & 0011 = 0001)
Bitwise OR	`	`	Performs OR on each bit
Bitwise XOR	^	Performs XOR (exclusive OR) on each bit	5 ^ 3 = 6 (0101 ^ 0011 = 0110)
Bitwise NOT	~	Inverts each bit	~5 = -6 (Two's complement)
Left Shift	<<	Shifts bits to the left	5 << 1 = 10 (0101 → 1010)
Right Shift	>>	Shifts bits to the right	5 >> 1 = 2 (0101 → 0010)

• Bitwise AND (&) is useful for bit masking.
• Bitwise OR (|) is used to set bits.
• Bitwise XOR (^) is used for toggling bits and encryption.
• Left shift (<<) is equivalent to multiplying by powers of two.
• Right shift (>>) is equivalent to integer division by powers of two.

Practical Bitwise Operations

Setting a Bit (Bit Masking with OR |)

To set a specific bit to 1:

num = num | (1 << bitPosition);

Example: Setting the 3rd Bit of num (Starting from 0)

#include <stdio.h>
int main() {
    int num = 5;  // Binary: 0101
    num |= (1 << 2);  // Set bit at position 2
    printf("New value: %d\n", num);  // Output: 7 (0111)
    return 0;
}

tip

Use Case: Setting feature flags, permissions, or hardware registers.

Clearing a Bit (Using AND & and NOT ~)

To clear a specific bit (set it to 0):

num = num & ~(1 << bitPosition);

Example: Clearing the 2nd Bit of num

#include <stdio.h>
int main() {
    int num = 7;  // Binary: 0111
    num &= ~(1 << 2);  // Clear bit at position 2
    printf("New value: %d\n", num);  // Output: 3 (0011)
    return 0;
}

tip

Use Case: Disabling specific bits in configuration settings.

Toggling a Bit (Using XOR ^)

To toggle (flip) a specific bit:

num = num ^ (1 << bitPosition);

Example: Toggling the 1st Bit of num

#include <stdio.h>
int main() {
    int num = 5;  // Binary: 0101
    num ^= (1 << 1);  // Toggle bit at position 1
    printf("New value: %d\n", num);  // Output: 7 (0111)
    return 0;
}

tip

Use Case: Useful in encryption and bit manipulation algorithms.

Bitwise Shifting (<<, >>)

Left Shift (<<) – Multiplication by Powers of 2

Shifting left multiplies by 2^n.

#include <stdio.h>
int main() {
    int num = 3;
    printf("%d\n", num << 1);  // Output: 6
    printf("%d\n", num << 2);  // Output: 12
    return 0;
}

tip

Use Case: Fast multiplication without using *.

Right Shift (>>) – Division by Powers of 2

Shifting right divides by 2^n.

#include <stdio.h>
int main() {
    int num = 16;
    printf("%d\n", num >> 1);  // Output: 8
    printf("%d\n", num >> 2);  // Output: 4
    return 0;
}

tip

Use Case: Fast division without using /.

Checking If a Number is Even or Odd (Using &)

#include <stdio.h>
int main() {
    int num = 7;
    if (num & 1)
        printf("Odd\n");
    else
        printf("Even\n");
    return 0;
}

tip

Why? Even numbers end in 0 in binary, and odd numbers end in 1.