# C Program to Find Twos Complement of a Binary Number

In this C program, we will learn about how to find two complement of a binary number.

#### Required Knowledge

Algorithm to find twos complement of a binary number
• 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.
• 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;

printf("Enter a Binary Number\n");
scanf("%s", binaryNumber);

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
```

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