Char bufP[255];

  UInt16 bufLen;

  Err retval;

  Int16    count,x,y; x=y=0;

  UInt8    checkSum;

  Char    checksumStr[2];

     // holds the dash and the checksum digit

 

  retval = SysGetROMToken (0, sysROMTokenSnum,(UInt8**)&bufP, &bufLen);

  if ((!retval) && (bufP) && ((UInt8) *bufP != 0xFF))

  {

     // there's a valid serial number!

     // Calculate the checksum:  Start with zero, add each digit,

     // then rotate the result one bit to the left and repeat.

        checkSum = 0;

        for (count=0; count<bufLen; count++)

        {

           checkSum += bufP[count];

           checkSum = (checkSum<<1) | ((checkSum & 0x80) >> 7);

        }

     // Add the two hex digits (nibbles) together, +2

     // (range: 2 - 31 ==> 2-9, A-W)

     // By adding 2 to the result before converting to ascii,

     // we eliminate the numbers 0 and 1, which can be

     // difficult to distinguish from the letters O and I.

     checkSum = ((checkSum>>4) & 0x0F) + (checkSum & 0x0F) + 2;

 

     // draw the serial number and find out how wide it was

     WinDrawChars(bufP, bufLen, x, y);

     x += FntCharsWidth(bufP, bufLen);

 

     // draw the dash and the checksum digit right after it

     checksumStr[0] = '-';

     checksumStr[1] =((checkSum < 10) ? (checkSum +'0'):(checkSum -10 +'A'));

     WinDrawChars (checksumStr, 2,x,y);

  }

    else // there's no serial number

        WinDrawChars("noNumberMessage",15,x, y);