C program to toggle or invert nth bit of a number

Write a C program to input any number from user and toggle or invert or flip nth bit of the given number using bitwise operator. How to toggle nth bit of a given number using bitwise operator in C programming. C program set nth bit of a given number if it is unset otherwise unset if it is set.

Example

Input

Input number: 22
Input nth bit to toggle: 1

Output

After toggling nth bit: 20 (in decimal)

Required knowledge

Bitwise operators, Data types, Variables and Expressions, Basic input/output

Logic to toggle nth bit of a number

Toggling bit means setting a bit in its complement state. Means if bit is currently set then change it to unset and vice versa.

To toggle a bit we will use bitwise XOR ^ operator. Bitwise XOR operator evaluates to 1 if corresponding bit of both operands are different otherwise evaluates to 0. We will use this ability of bitwise XOR operator to toggle a bit. For example - if Least Significant Bit of num is 1, then num ^ 1 will make LSB of num to 0. And if LSB of num is 0, then num ^ 1 will toggle LSB to 1.

Step by step descriptive logic to toggle nth bit of a number.

  1. Input number and nth bit position to toggle from user. Store it in some variable say num and n.
  2. Left shift 1 to n times, i.e. 1 << n.
  3. Perform bitwise XOR with num and result evaluated above i.e. num ^ (1 << n);.

Program to toggle or invert nth bit

/**
 * C program to toggle nth bit of a number
 */

#include <stdio.h>

int main()
{
    int num, n, newNum;

    /* Input number from user */
    printf("Enter any number: ");
    scanf("%d", &num);

    /* Input bit position you want to toggle */
    printf("Enter nth bit to toggle (0-31): ");
    scanf("%d", &n);

    /*
     * Left shifts 1, n times
     * then perform bitwise XOR with num
     */
    newNum = num ^ (1 << n);

    printf("Bit toggled successfully.\n\n");
    printf("Number before toggling %d bit: %d (in decimal)\n", n, num);
    printf("Number after toggling %d bit: %d (in decimal)\n", n, newNum);

    return 0;
}

Output

Enter any number: 22
Enter nth bit to toggle (0-31): 1
Bit toggled successfully.

Number before toggling 1 bit: 22 (in decimal)
Number after toggling 1 bit: 20 (in decimal)

Happy coding 😉

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