The CHIPMUNK DISK PEEKER/POKER

                                  By Tim Ekdom


            DISKPP.BA is a disk  utility  program  that  enables  us  to
        discover how CDOS and the Chipmunk store our files on disk.   It
        also enables us to attempt recovery of files that have been lost
        due to corruption of data on  the  disk  or  due  to  unintended
        deletion.


        CDOS DISK FORMAT

            CDOS organizes the disk into 80 tracks, numbered  0  through
        79.  Each track has 18 sectors, numbered  1  through  18.   Each
        sector contains 256 bytes of data.  Each track is also organized
        into three clusters, each containing six  sectors.   Thus  there
        are 240 clusters per disk, numbered from 0 through 239.

            CDOS  organizes  the  files  stored   on   the   disk   into
        directories.  Each directory has room for up to 24 entries.  The
        type of file organization used is often called a "tree"  because
        the main directory is like the trunk of a  tree  which  branches
        into sub-directories like the  branches  of  a  tree.   The  top
        directory, or "trunk" will be referred to as the main directory.
        The  "branches"  will  be  referred  to  as  sub-directories  or
        "folders"  (which  is  the  term  that  CDOS  uses  for  a  sub-
        directory).  Each directory has a name: the main  directory  has
        the disk name and sub-directories  have  a  folder  name.   Each
        folder may contain both files and folders.   Files  and  folders
        are visible on the menu only when you  are  located  within  the
        directory in which they are contained.

            CDOS keeps track of where each  file  is  stored  through  a
        directory entry for each folder in combination  with  a  cluster
        allocation table.  The main directory and allocation  table  are
        stored in cluster 0, which is on track 0.  Each sub-directory is
        stored in its own cluster.

            A directory has space for  26  "slots",  each  18  bytes  in
        length.   The  directory  name  (or  disk  name  for  the   main
        directory) and the first twelve entries are in the first  sector
        of the directory cluster, and the name (again)  and  the  second
        twelve entries are in the third sector.  A copy of the same data
        is kept in the same format on second and fourth sectors  in  the
        cluster.  The directory name uses only 10 bytes of the first  18
        byte slot.  The rest have the following format:





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                Bytes    Usage
                    1    entry type
                 2-10    entry name (folder in lower case,
                         file in upper case)
                   11    number of bytes in last sector
                         of last unfilled cluster
                   12    number of cluster where entry starts
                13-14    date created
                15-16    date modified
                17-18    unused at present

            The entry types are as follows:

                Value    Type
                240      this entry is a folder
                128      BA file
                160      CO file
                192      DO file
                  0      this entry slot is available

            If the entry is a folder, the byte  containing  the  cluster
        number designates the cluster where the  sub-directory  will  be
        found.

            The allocation table is in sectors five and six  of  cluster
        0, one copy in each sector.  It uses 240  bytes,  one  byte  for
        each cluster, numbered 0 - 239.  If the value of the  associated
        byte is zero, then that cluster is available for use.  If it  is
        1 - 239, then that cluster is in use, is full, and the  file  it
        contains is continued in another cluster. The value of the  byte
        is the number of the cluster where the file is continued. If the
        end of the file is within that  cluster,  it  will  contain  the
        value 240-246, where the number of sectors the file occupies  in
        that sector can be found by subtracting 240.  For example:

                Byte     Contents
                   5            6
                   6            7
                   7          242

            The file  starting in cluster 5 is continued  in  cluster  6
        and on into cluster 7, where it ends.  It occupies  two  sectors
        of cluster 7. The directory entry for  that  file  contains  the
        number of bytes found in the second sector of cluster 7.  If the
        byte's value is 254, that cluster has been  marked  by  CDOS  as
        unavailable for use.










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