1.13 Bit Manipulation in C Programming

Module 1.13 • Bitwise Logic Operations, Masking Formulas & Low-Level Data Modification

1.13.1 Introduction

Computers store all information using binary digits (bits).

A bit can have only two values:

Normally, programmers work with bytes, integers, characters, and other data types. However, some applications require direct control over individual bits. This process is called Bit Manipulation.

Bit manipulation is widely used in:

Embedded systems
Device drivers
Operating systems
Networking software
Cryptography
Real-time applications

1.13.2 What is a Bit?

A bit is the smallest unit of data.

Example:

Decimal Number = 45

Binary Representation

00101101

Each position represents a power of 2.

Bit Position

7	6	5	4	3	2	1	0
0	0	1	0	1	1	0	1

1.13.3 Why Use Bit Manipulation?

Advantages:

Faster execution
Reduced memory usage
Efficient flag handling
Better hardware control
Useful in low-level programming

1.13.4 Bitwise Operators in C

Operator	Name
`&`	AND
`\|`	OR
`^`	XOR
`~`	NOT (Complement)
`<<`	Left Shift
`>>`	Right Shift

1.13.5 Bitwise AND Operator (&)

The AND operator returns 1 only when both bits are 1.

Truth Table

A	B	A&B
0	0	0
0	1	0
1	0	0
1	1	1

Example

Calculation:

Result:

1.13.6 AND Program

#include <stdio.h>
 
int main()
{
    int a = 12;
    int b = 10;
 
    printf("%d", a & b);
 
    return 0;
}

Output:

1.13.7 Bitwise OR Operator (|)

Returns 1 if at least one bit is 1.

Truth Table

A	B	A\|B
0	0	0
0	1	1
1	0	1
1	1	1

Example

12 = 1100
10 = 1010

Result:

1.13.8 OR Program

#include <stdio.h>
 
int main()
{
    int x = 12;
    int y = 10;
 
    printf("%d", x | y);
 
    return 0;
}

Output:

1.13.9 Bitwise XOR Operator (^)

Returns 1 when bits are different.

Truth Table

A	B	A^B
0	0	0
0	1	1
1	0	1
1	1	0

Example

12 = 1100
10 = 1010

Result:

1.13.10 XOR Program

#include <stdio.h>
 
int main()
{
    int a = 12;
    int b = 10;
 
    printf("%d", a ^ b);
 
    return 0;
}

Output:

1.13.11 Bitwise NOT Operator (~)

NOT reverses every bit.

0 → 1
1 → 0

Example:

7 = 00000111

After NOT:

11111000

Result (2's complement):

-8

1.13.12 NOT Program

#include <stdio.h>
 
int main()
{
    int num = 7;
 
    printf("%d", ~num);
 
    return 0;
}

Output:

-8

1.13.13 Left Shift Operator (<<)

Moves bits toward the left. Each shift multiplies the number by 2.

Example

9 = 00001001
 
9 << 1

Result:

00010010

Decimal:

1.13.14 Left Shift Program

#include <stdio.h>
 
int main()
{
    int value = 9;
 
    printf("%d", value << 1);
 
    return 0;
}

Output:

1.13.15 Right Shift Operator (>>)

Moves bits toward the right. Each shift approximately divides by 2.

Example

20 = 00010100
 
20 >> 2

Result:

00000101

Decimal:

1.13.16 Right Shift Program

#include <stdio.h>
 
int main()
{
    int num = 20;
 
    printf("%d", num >> 2);
 
    return 0;
}

Output:

1.13.17 Multiplication Using Shift

Number × 2ⁿ can be performed as number << n

Example:

11 << 3

Calculation:

11 × 8 = 88

Result:

1.13.18 Division Using Shift

80 >> 4

Calculation:

80 ÷ 16

Result:

1.13.19 Checking Even or Odd

The least significant bit determines parity.

Even → Last bit = 0
Odd  → Last bit = 1

1.13.20 Program to Check Even/Odd

#include <stdio.h>
 
int main()
{
    int num = 37;
 
    if(num & 1)
        printf("Odd");
    else
        printf("Even");
 
    return 0;
}

Output:

Odd

1.13.21 Understanding Bit Positions

Bit Position

7	6	5	4	3	2	1	0

Position numbering begins from the right.

1.13.22 Creating a Mask

A mask helps manipulate a specific bit.

Formula:

mask = 1 << position;

Example:

mask = 1 << 4;

Result:

00010000

1.13.23 Testing a Bit

Check whether a bit is ON or OFF.

if(number & mask)

Example:

int number = 26;
int mask = 1 << 3;

1.13.24 Program to Test a Bit

#include <stdio.h>
 
int main()
{
    int number = 26;
    int position = 3;
 
    if(number & (1 << position))
        printf("Bit is ON");
    else
        printf("Bit is OFF");
 
    return 0;
}

Output:

Bit is ON

1.13.25 Setting a Bit

Setting means turning a bit ON.

Formula:

number |= mask;

Example

Number = 18

00010010

Set Bit 0:

00010011

Result:

1.13.26 Program to Set a Bit

#include <stdio.h>
 
int main()
{
    int number = 18;
 
    number |= (1 << 0);
 
    printf("%d", number);
 
    return 0;
}

Output:

1.13.27 Clearing a Bit

Clearing means turning a bit OFF.

Formula:

number &= ~(1 << position);

1.13.28 Example

22 = 10110

Clear bit 2:

Result:

1.13.29 Program to Clear a Bit

#include <stdio.h>
 
int main()
{
    int number = 22;
 
    number &= ~(1 << 2);
 
    printf("%d", number);
 
    return 0;
}

Output:

1.13.30 Toggling a Bit

Toggle means:

0 → 1
1 → 0

Formula:

number ^= (1 << position);

1.13.31 Toggle Example

20 = 10100

Toggle bit 1:

Result:

1.13.32 Program to Toggle a Bit

#include <stdio.h>
 
int main()
{
    int number = 20;
 
    number ^= (1 << 1);
 
    printf("%d", number);
 
    return 0;
}

Output:

1.13.33 Extracting a Bit

Formula:

(number >> position) & 1

Example

int value = 45;
int bit = (value >> 2) & 1;

Result:

1.13.34 Swapping Numbers Using XOR

No temporary variable required.

a ^= b;
b ^= a;
a ^= b;

1.13.35 Program to Swap Numbers

#include <stdio.h>
 
int main()
{
    int a = 14;
    int b = 25;
 
    a ^= b;
    b ^= a;
    a ^= b;
 
    printf("%d %d", a, b);
 
    return 0;
}

Output:

25 14

1.13.36 Counting Set Bits

Set bit means a bit whose value is 1.

Example:

29 = 11101

Set Bits:

1.13.37 Program to Count Set Bits

#include <stdio.h>
 
int main()
{
    int num = 29;
    int count = 0;
 
    while(num)
    {
        num &= (num - 1);
        count++;
    }
 
    printf("%d", count);
 
    return 0;
}

Output:

1.13.38 Binary Flag Storage

One integer can store many flags.

Example:

Bit 0 → Read Permission
Bit 1 → Write Permission
Bit 2 → Execute Permission
Bit 3 → Hidden File

1.13.39 Defining Flags

#define READ    0x01
#define WRITE   0x02
#define EXECUTE 0x04
#define HIDDEN  0x08

1.13.40 Enabling Flags

flags |= READ;
flags |= WRITE;

1.13.41 Disabling Flags

flags &= ~WRITE;

1.13.42 Checking Flags

if(flags & READ)
{
    printf("Read Enabled");
}

1.13.43 Binary Pattern Display Logic

To print all bits:

for(i=15;i>=0;i--)
{
    printf("%d", (num>>i)&1);
}

1.13.44 Applications of Bit Manipulation

Used in:

Embedded controllers
Device drivers
Communication protocols
Compression algorithms
Encryption systems
Network packet processing

1.13.45 Advantages

Very fast execution
Efficient memory usage
Low-level hardware access
Useful for flag management
Improves performance

Summary

Bit manipulation operates directly on binary digits.
C provides six bitwise operators.
AND tests and clears bits.
OR sets bits.
XOR toggles bits.
NOT complements bits.
Left shift multiplies by powers of 2.
Right shift divides by powers of 2.
Masks help manipulate specific bits.
Bit manipulation is widely used in systems and embedded programming.

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