944-959



     Bit  7   6   5   4   3   2   1   0
     Use  ....unused....  W   R   D   A

     W equals write, R equals read, D equals directory, A equals
     append.

     ICAX2     11      1     Auxiliary byte two, referred
     to as AUX2. Special use by each device driver; some serial port
     functions may use this byte. Auxiliary bytes two to five have no
     fixed use; they are used to contain device-dependent and/or
     user-established data.

     ICAX3/4   12,13   2     Auxiliary bytes three and
     four; used to maintain a record of the disk sector number for the
     BASIC NOTE and POINT commands.

     ICAX5     14      1     Auxiliary byte five. Used by
     NOTE and POINT to maintain a record of the byte within a sector.
     It stores the relative displacement in sector from zero to 124
     ($7C). Bytes 125 and 126 of a sector are used for sector-link
     values, and byte 127 ($7F) is used as a count of the number of
     data bytes in actual use in that sector.

     ICAX6     15      1     Spare auxiliary byte.

     Offset is the number you would add to the start of the IOCB in
     order to POKE a value into the right field, such as POKE 832 +
     OFFSET, 12.

     The following is a list of the values associated with OPEN
     parameter number 1. Most of these values are listed in Your Atari
     400/800. These are the values found in ICAX1, not the ICCOM
     values.

     Device        Task #    Description
     ----------------------------------------------------------------------
     Cassette       4        Read
     recorder       8        Write (can do either, not both)

     Disk           4        Read
     file           6        Read disk directory
                    8        Write new file. Any file OPENed in
     this mode will be deleted, and the first byte written will be at the
     start of the file.
                    9        Write--append. In this mode the
     file is left intact, and bytes written are put at the end of the file.
                   12        Read and write--update. Bytes
     read or written will start at the first byte in the file.

     D: if BIT 0 equals one and BIT 3 equals one in AUX1,then
     operation will be appended output.

     Screen         8        Screen output
     editor        12        Keyboard input and screen output