week 10a C program on 2's Compliment

/*
Write a C program to find the 2’s complement of a binary number
*/

#include <stdio.h>

#include<conio.h>

void complement (char *a);

void main()

{

 char a[16];

 int i;

 clrscr();

 printf("Enter the binary number");

 gets(a);

 for(i=0;a[i]!='\0'; 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[16];

 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]='\0';

printf("The 2's complement is %s", b);

}