# C Program to Find Twos Complement of a Binary Number

• Write a C program to read a binary number and find its two’s complement.
• Wap in C to find two complement of a binary number.

Required Knowledge

Algorithm to find twos complement of a binary number
1. To find the twos complement of a number first find the ones complement by toggling the bits of the number. Change all 1's to 0's and all 0's to 1's.
2. Add binary 1 to the ones complement to get twos complement.


For Example :
Binary Number = 00101011
Ones Complement = 11010100
Twos Complement = 11010101

## C program to find two complement of a binary number #include <stdio.h>
#include <string.h>

int main() {
char binaryNumber, onesComplement, twosComplement;
int counter, error=0, digitCount, carry = 1;
/*
* Take a binary string as input from user
*/
printf("Enter a Binary Number\n");
scanf("%s", binaryNumber);

/*
* To get one's complement, we toggle
* 1's to 0's and 0's to 1's
*/
digitCount = strlen(binaryNumber);

for(counter=0; counter < digitCount; counter++) {
if(binaryNumber[counter]=='1') {
onesComplement[counter] = '0';
} else if(binaryNumber[counter]=='0') {
onesComplement[counter] = '1';
} else {
printf("Error :( ");
return 1;
}
}
onesComplement[digitCount] = '\0';

/*
*/
for(counter = digitCount-1; counter >= 0; counter--) {
if(onesComplement[counter]=='1' && carry==1){
twosComplement[counter] = '0';
} else if(onesComplement[counter]=='0' && carry==1) {
twosComplement[counter] = '1';
carry = 0;
} else {
twosComplement[counter] = onesComplement[counter];
}
}
twosComplement[digitCount] = '\0';

printf("Two's Complement : %s", twosComplement);

return 0;
}

Output

Enter a Binary Number
11100001
Two's Complement : 00011111