# C program to find the 2’s complement of a binary number.

C Program to calculate the 2’s complement of a binary number. 2’s complement of a number is obtained by scanning it from right to left and complementing all the bits after the first appearance of a 1. Thus 2’s complement of 11100 is 00100. Read more about C Programming Language .

`/************************************************************ You can use all the programs on  www.c-program-example.com* for personal and learning purposes. For permissions to use the* programs for commercial purposes,* contact [email protected]* To find more C programs, do visit www.c-program-example.com* and browse!* *                                  Happy Coding***********************************************************/#include <stdio.h>#include<conio.h>void complement (char *a);void main(){ char a; int i; clrscr(); printf("Enter the binary number"); gets(a); for(i=0;a[i]!=''; i++) {  if (a[i]!='0' && a[i]!='1')  {   printf("The number entered is not a binary number. Enter the correct number");   exit(0);  } }complement(a);getch();}void complement (char *a){ int l, i, c=0; char b; l=strlen(a); for (i=l-1; i>=0; i--) {  if (a[i]=='0')  b[i]='1';  else  b[i]='0'; } for(i=l-1; i>=0; i--) { if(i==l-1) {  if (b[i]=='0')  b[i]='1';  else  {   b[i]='0';   c=1;  } } else {  if(c==1 && b[i]=='0')  {   b[i]='1';   c=0;  } else if (c==1 && b[i]=='1') {  b[i]='0';  c=1; }}}b[l]='';printf("The 2's complement is %s", b);}`
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