*** FilePacked ZipCode (A!xxxxxx, B!xxxxxx, etc)
*** Document revision: 1.4
*** Last updated: March 11, 2004
*** Compiler/Editor: Peter Schepers
*** Contributors/sources: Joe Forster/STA

  This is another rarely seen format, and is very similar to the Diskpacked
(4-pack) Zipcode in structure. It is comprised of a series of files denoted
by A!xxxxxx and B!xxxxxx, with letters instead  of  numbers  as  the  first
characters of the filename. It also contains one other file called X!xxxxxx
which contains a directory of the files stored in the overall archive. Here
is the layout of the files:

      00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F        ASCII
      -----------------------------------------------   ----------------
0000: FF 03 A6 11 0A 01 08 0E 08 CE 07 9E 20 28 32 30   �������������(20
0010: 36 34 29 00 00 00 78 A9 34 85 01 A2 05 BD 42 08   64)���x�4�����B�
0020: 9D 2D 00 CA 10 F7 9A A0 00 C6 32 CE 2C 08 B1 31   �-��������2�,��1
0030: 99 00 00 C8 D0 F8 A5 32 C9 08 D0 ED B9 48 08 99   �������2�����H��
0040: 00 01 C8 D0 F7 4C 00 01 01 08 46 4D F3 BB B1 2F   �����L����FM�/

  Bytes: 00-01: Load Address, low/high format, usually $FF $03, or $03FF)
            02: Number of sectors in the file (maximum 166, or $A6)
         03-??: Zipcoded sector data starts here

  If 166 sectors was not enough to store the file then more x!xxxxxx  files
are needed, and the layout is the same. This makes the resulting file  size
of each section approximately the same as the 4-pack zipcode would  be,  as
166 sectors is 1/4 of a normal D64 (664 sector) disk.

  The sector information is zipcoded  in  the  same  manner  as  Diskpacked
4-pack Zipcodes, but the sector size (excluding the t/s link) is 254 bytes,
not 256 as in 4-pack zipcode. The compression is still stored  in  the  top
two bits of the track link, and the remainder of the sector (254 bytes)  is
encoded. Each block of the file is stored  in  full,  even  the  last  one,
though it is rarely completely used.

  Bits
  ----
   00 - No compression, the sector is stored in full. The  next  254  bytes
        contains the remainder of the sector information.
   01 - Sector is filled with *one* character. The next  character  is  the
        fill byte. Repeat it 254 times, and fill the sector.
   10 - Sector is compressed using RLE compression (see 4-pack ZipCode  for
        details)
   11 - Unused

  If the track is decoded as $00, then we are on  the  last  block  of  the
file, and the sector represents the number of bytes used.


  The special file, X!xxxxxx, as mentioned above, contains a listing of all
the files in the archive. It has most of the information that the  D64/1541
entry would. Here is the layout:


      00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F        ASCII
      -----------------------------------------------   ----------------
0000: 01 08 0B 08 00 00 9E 32 30 36 31 00 00 00 A0 00   �������2061�����
0010: 8C 20 D0 8C 21 D0 B9 C7 08 F0 06 20 D2 FF C8 D0   ��Ќ!й���������
0020: F5 85 FF 85 FB A0 0A 84 FC 85 FD 85 FE A0 11 B1   ����������������
0030: FB 48 AA C8 B1 FB 48 A8 20 4B 09 20 41 09 8A 20   �H�ȱ�H��K��A���
0040: 41 09 98 20 41 09 68 AA 68 18 65 FD 85 FD 8A 65   A���A�h�h�e����e
0050: FE 85 FE 20 39 09 20 3C 09 A0 00 B1 FB C9 A0 F0   ����9��<�����ɠ�
0060: 08 20 41 09 C8 C0 10 D0 F2 20 3C 09 C0 13 F0 06   ��A�������<�����
0070: 20 39 09 C8 D0 F6 A0 10 B1 FB 29 7F 20 41 09 20   �9��������)�A��
0080: 3F 09 A5 FB 18 69 15 85 FB 90 02 E6 FC E6 FF A5   ?����i����������
0090: FF CD FF 09 D0 97 AA A0 00 20 4B 09 8E 08 09 8C   ��������K�����
00A0: 09 09 A6 FD A4 FE 20 4B 09 8D 1A 09 8E 1B 09 8C   �������K��������
00B0: 1C 09 AD FE 09 09 30 8D 2D 09 A0 00 B9 F7 08 F0   ������0�-�������
00C0: 06 20 41 09 C8 D0 F5 60 93 9B 11 11 11 11 11 11   ��A����`��������
00D0: 11 11 11 11 11 11 11 11 11 11 48 4F 4C 44 20 53   ����������HOLD�S
00E0: 54 4F 50 20 54 4F 20 50 41 55 53 45 20 4C 49 53   TOP�TO�PAUSE�LIS
00F0: 54 49 4E 47 3A 0D 0D 00 0D 0D 54 4F 54 41 4C 20   TING:�����TOTAL�
0100: 46 49 4C 45 53 20 20 3D 20 30 30 0D 54 4F 54 41   FILES��=�00�TOTA
0110: 4C 20 42 4C 4F 43 4B 53 20 3D 20 30 30 30 0D 50   L�BLOCKS�=�000�P
0120: 41 43 4B 45 44 20 46 49 4C 45 53 20 3D 20 30 0D   ACKED�FILES�=�0�
0130: 05 5B 5A 43 20 49 49 5D 0D 00 A9 20 2C A9 22 2C   �[ZC�II]����,�",
0140: A9 0D 20 D2 FF A5 91 C9 7F F0 FA 60 8E 92 09 8C   ����������`����
0150: 93 09 A0 02 A9 30 99 96 09 88 10 FA A2 02 AD 92   �����0����������
0160: 09 38 FD 8F 09 8D 94 09 AD 93 09 E9 00 8D 95 09   �8��������������
0170: 90 11 AD 94 09 8D 92 09 AD 95 09 8D 93 09 FE 96   ����������������
0180: 09 D0 DB CA 10 D8 AD 98 09 AE 97 09 AC 96 09 60   �����ح��������`
0190: 01 0A 64 00 00 00 00 31 32 33 00 00 00 00 00 00   ��d����123������
01A0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00   ����������������
01B0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00   ����������������
01C0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00   ����������������
01D0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00   ����������������
01E0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00   ����������������
01F0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 04   ����������������
0200: 0E 4D 55 53 49 43 20 53 45 4C 45 43 54 4F 52 A0   �MUSIC�SELECTOR�
0210: A0 D0 B6 00 11 00 31 30 30 31 20 4C 45 54 54 45   ���1001�LETTE
0220: 52 20 2D 56 2D A0 D0 72 00 13 00 4E 45 57 20 4D   R�-V-��r���NEW�M
0230: 41 49 4C 2F 44 44 A0 A0 A0 A0 A0 D0 1E 00 19 00   AIL/DD����������
0240: 4A 41 43 4B 20 54 48 45 20 4E 49 50 50 45 52 A0   JACK�THE�NIPPER�
0250: D0 C0 00 1A 06 54 55 52 4E 45 52 20 49 49 A0 A0   �����TURNER�II��
0260: A0 A0 A0 A0 A0 D0 2B 00 07 00 53 43 52 45 45 4E   ������+���SCREEN
0270: 20 20 30 A0 A0 A0 A0 A0 A0 A0 D3 07 00 05 00 53   ��0������������S
0280: 43 52 45 45 4E 20 20 31 A0 A0 A0 A0 A0 A0 A0 D3   CREEN��1��������
0290: 0C 00 05 01 53 43 52 45 45 4E 20 20 32 A0 A0 A0   ����SCREEN��2���
02A0: A0 A0 A0 A0 D3 0B 00 04 00 53 43 52 45 45 4E 20   ���������SCREEN�
02B0: 20 33 A0 A0 A0 A0 A0 A0 A0 D3 02 00 04 01 53 43   �3������������SC
02C0: 52 45 45 4E 20 20 34 A0 A0 A0 A0 A0 A0 A0 D3 03   REEN��4���������
02D0: 00 04 03 53 43 52 45 45 4E 20 20 35 A0 A0 A0 A0   ���SCREEN��5����
02E0: A0 A0 A0 D3 07 00 04 07 53 43 52 45 45 4E 20 20   ��������SCREEN��
02F0: 36 A0 A0 A0 A0 A0 A0 A0 D3 08 00 03 00 53 43 52   6������������SCR
0300: 45 45 4E 20 20 37 A0 A0 A0 A0 A0 A0 A0 D3 07 00   EEN��7����������
0310: 03 01 53 43 52 45 45 4E 20 20 38 A0 A0 A0 A0 A0   ��SCREEN��8�����
0320: A0 A0 D3 0B 00 03 09 .. .. .. .. .. .. .. .. ..   �������.........

  Bytes: 0000-01FE: BASIC program which lists the contents of  the  archive
                    (a SYS 2061 call to an ML program)
              01FF: Number of archive (x!xxxxxx)  files.  Since  the  upper
                    value is  4,  we  have  A!xxxxxx,  B!xxxxxx,  C!xxxxxx,
                    D!xxxxxx and X!xxxxxx.
              0200: Number of C64 files contained in the directory (14)
              0201: Start of the directory

  Each file has a directory entry in the X!xxxxxx file, starting at  $0201,
each 21 bytes long, and laid out as follows:

      00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F        ASCII
      -----------------------------------------------   ----------------
0200: .. 4D 55 53 49 43 20 53 45 4C 45 43 54 4F 52 A0   .MUSIC�SELECTOR�
0210: A0 D0 B6 00 11 00 31 30 30 31 20 4C 45 54 54 45   ���1001�LETTE
0220: 52 20 2D 56 2D A0 D0 72 00 13 00 4E 45 57 20 4D   R�-V-��r���NEW�M
0230: 41 49 4C 2F 44 44 A0 A0 A0 A0 A0 D0 1E 00 19 00   AIL/DD����������
0240: 4A 41 43 4B 20 54 48 45 20 4E 49 50 50 45 52 A0   JACK�THE�NIPPER�
0250: D0 C0 00 1A 06 54 55 52 4E 45 52 20 49 49 A0 A0   �����TURNER�II��
0260: A0 A0 A0 A0 A0 D0 2B 00 07 00 53 43 52 45 45 4E   ������+���SCREEN
0270: 20 20 30 A0 A0 A0 A0 A0 A0 A0 D3 07 00 05 00 53   ��0������������S
0280: 43 52 45 45 4E 20 20 31 A0 A0 A0 A0 A0 A0 A0 D3   CREEN��1��������
0290: 0C 00 05 01 53 43 52 45 45 4E 20 20 32 A0 A0 A0   ����SCREEN��2���
02A0: A0 A0 A0 A0 D3 0B 00 04 00 53 43 52 45 45 4E 20   ���������SCREEN�
02B0: 20 33 A0 A0 A0 A0 A0 A0 A0 D3 02 00 04 01 53 43   �3������������SC
02C0: 52 45 45 4E 20 20 34 A0 A0 A0 A0 A0 A0 A0 D3 03   REEN��4���������
02D0: 00 04 03 53 43 52 45 45 4E 20 20 35 A0 A0 A0 A0   ���SCREEN��5����
02E0: A0 A0 A0 D3 07 00 04 07 53 43 52 45 45 4E 20 20   ��������SCREEN��
02F0: 36 A0 A0 A0 A0 A0 A0 A0 D3 08 00 03 00 53 43 52   6������������SCR
0300: 45 45 4E 20 20 37 A0 A0 A0 A0 A0 A0 A0 D3 07 00   EEN��7����������
0310: 03 01 53 43 52 45 45 4E 20 20 38 A0 A0 A0 A0 A0   ��SCREEN��8�����
0320: A0 A0 D3 0B 00 03 09 .. .. .. .. .. .. .. .. ..   �������.........

  Bytes:$00-0F: 16 character filename (PETASCII, padded with $A0)
            10: Filetype: (the character "P" "S" or "U"  OR'd  with  0x80).
                This means that the write-protect and splat bits are  *not*
                transferred, neither are custom file types, and REL is  not
                allowed either.
         11-12: Length of the file in sectors (0 for no size)
         13-14: Original starting track/sector of the file

  In order to extract *one* specific file,  you  would  have  to  read  the
entire archive until you came across the directory entry that  you  wanted,
then process that specific file. This format does not  contain  any  offset
references in the central directory for each file, just the  original  file
size, which means that we don't know anything about where a file  might  be
in the archive, since the original sector size doesn't apply as the  stored
file in compressed.

  Since this format seems to be uncommon, I can't see any benefit of  using
it over LNX as a  native  C64  file.  The  only  plus  is  it  uses  simple
compression, whereas LNX does not. However, LNX only uses one file for  the
entire file set stored.