31



     buffer size and line size equals 40 bytes; double-width print
     equals 20 bytes (most printers use their own control codes for
     expanded print); sideways printing equals 29 bytes (Atari 820
     printer only). Printer status request equals four. PBUFSZ is
     initialized to 40. The printer handler checks to see if the same
     value is in PBPNT and, if so, sends the contents of the buffer to
     the printer.

31             1F             PTEMP
     Temporary register used by the printer handler for the value of
     the character being output to the printer.

----------------------------------------------------------------------

Locations 32 to 47 ($20 to $2F) are the ZIOCB: Page zero Input-Output
Control Block. They use the same structure as the IOCB's at locations
832 to 959 ($340 to $3BF). The ZIOCB is used to communicate I/O con-
trol data between CIO and the device handlers. When a CIO opera-
tion is initiated, the information stored in the IOCB channel is moved
here for use by the CIO routines. When the operation is finished, the
updated information is returned to the user area.

32             20             ICHIDZ
     Handler index number. Set by the OS as an index to the device
     name table for the currently open file. If no file is open on this
     IOCB (IOCB free), then this register is set to 255 ($FF).

33             21             ICDNOZ
     Device number or drive number Called MAXDEV by DOS to in-
     dicate the maximum number of devices. Initialized to one.

34             22             ICCOMZ
     Command code byte set by the user to define how the rest of the
     IOCB is formatted, and what I/O action is to be performed.

35             23             ICSTAZ
     Status of the last IOCB action returned by the device, set by the
     OS. May or may not be the same status returned by the STATUS
     command.

36,37          24,25          ICBALZ/HZ
     Buffer address for data transfer or the address of the file name for
     commands such as OPEN, STATUS, etc.

38,39          26,27          ICPTLZ/HZ
     Put byte routine address set by the OS. It is the address minus
     one byte of the device's "put one byte" routine. It points to CIO's
     "IOCB not OPEN" on a CLOSE statement.

40,41          28,29          ICBLLZ/HZ
     Buffer length byte count used for PUT and GET operations;