char * converti(char car)
   {
     switch(car)
      {
        case '0':
             return "0000";
        case '1':
             return "0001";
        case '2':
             return "0010";
        case '3':
             return "0011";
        case '4':
             return "0100";
        case '5':
             return "0101";
        case '6':
             return "0110";
        case '7':
             return "0111";
        case '8':
             return "1000";
        case '9':
             return "1001";
        case 'a':
             return "1010";
        case 'b':
             return "1011";
        case 'c':
             return "1100";
        case 'd':
             return "1101";
        case 'e':
             return "1110";
        case 'f':
             return "1111";
      }
     
     //  char stringa_bin[64];

     

   }