main()
{
 char b[50];
 int i,p=0,v=0;
 long int d=0;
 clrscr();
 printf("\n\n\t\tThis program will help you to find the decimal equivalent");
 printf("\n\t\t\t\tof a given binary number.");
 printf("\n\n\t\t       Enter number in front of the '->' prompt : ");
 printf("\n\n\t\t\t\t      -> ");
 scanf("%s",b);
 for(i=0;b[i]!='\0'; )
 {
   if((b[i]!='0')&&(b[i]!='1'))
   {
    clrscr();
    printf("\n\n\n\n\n\n\n\n\t\t\t\t  INPUT ERROR !");
    printf("\n\n\n\t\t\tThe number entered is not binary !");
    printf("\n\n\n\n\n\t\t   Press any key to return to source file.....");
    getch();
    exit();
   }
   else
     i=i+1;
 }
 i=i-1;
 while(i>=0)
 {
  p=p*2;
  if(p==0)
    p=1;
  if(b[i]=='1')
  {
   v=p*1;
   d=d+v;
   i=i-1;
  }
  else
    i=i-1;
 }
 printf("\n\n\n\n\t\t\t\t    - A N S W E R -");
 printf("\n\n\t\t\tThe decimal equivalent of ");
 for(i=0;b[i]!='\0';i++)
   printf("%c",b[i]);
 printf(" is %d.",d);
 getch();
}