main()
{
 char b[50];
 int i,p=0,v=0,x=1;
 long int d=0,display=1;
 clrscr();
 while(x!=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\tType 0 to Exit and 1 to Continue : ");
 scanf("%d",&x);
 switch(x)
 {
  case 1:
    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'; )
    {
     i=i+1;
     if((b[i]!='1')&&(b[1]!=0))
      display=0;
     else
      display=1;
    if(display==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();
    break;

  case 0:
    printf("\n\n\n\n\n\n\n\n\t\t\t\tPROGRAM TERMINATED !");
    printf("\n\n\n\t\t\tPress any key to return to source file.....");

  default:
    clrscr();
    printf("\n\n\n\n\n\n\n\n\t\t\t\tINVALID INPUT !");
    printf("\n\n\n\t\t\tPress any key to continue.....");
    getch();
    break;
  }
  else
  {
   clrscr();
   printf("\n\n\n\n\n\n\n\n\t\t\t\tINPUT ERROR !");
   printf("\n\n\n\t\t\tThe number is not binary !");
   printf("\n\n\n\n\t\t\tPress any key to continue.....");
   getch();
   break;
  }
  }
  }
 }
}