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C program to find ones complement of a binary number

C program to find ones complement of a binary number

Write a C program to input binary number from user and find ones complement of binary number using loop. How to find 1s complement of a binary number in C programming.

What is Ones complement?

Ones complement of a binary number is defined as value obtained by inverting all binary bits. It is the result of swapping all 1s to 0s and all 0s to 1s.

01101110  >>  10010001

Logic to find ones complement of a number

    Input a binary string from user. Store it in a variable say binary.
    Run a loop from 1 to length of binary string, increment 1 in each iteration. The loop structure should look like for(j=0; j<SIZE; j++) (where SIZE is the length of binary digit).
    Inside loop there are two possibilities -
        Print 0 for each 1 binary bit i.e. if(binary[j] == '1').
        Print 1 for each 0 binary bit i.e. if(binary[j] == '0').

#include <stdio.h>

#define SIZE 8

int main()
{
    char binary[SIZE + 1], onesComp[SIZE + 1];
    int j, error=0;

    printf("Enter %d bit binary value: ", SIZE);
    
    /* Input binary string from user */
    gets(binary);

    /* Store all inverted bits of binary value to onesComp */
    for(j=0; j<SIZE; j++)
    {
        if(binary[j] == '1')
        {
            onesComp[j] = '0';
        }
        else if(binary[j] == '0')
        {
            onesComp[j] = '1';
        }
        else
        {
            printf("Invalid Input");
            error = 1;

            /* Exits from loop */
            break;
        }
    }

    /* Marks the end of onesComp string */
    onesComp[SIZE] = '\0';

    /* Check if there are binary string contains no error */
    if(error == 0)
    {
        printf("Original binary = %s\n", binary);
        printf("Ones complement = %s", onesComp);
    }

    return 0;
}