Command             Command Operation
-------             -----------------
CBD_CHANGEHOOK      Specify a hook to be called when the data on the
                    clipboard has changed (V36).

CBD_CURRENTREADID   Return the Clip ID of the current clip to read.  This
                    is used to determine if a clip posting is still the
                    latest cut.

CBD_CURRENTWRITEID  Return the Clip ID of the latest clip written.  This
                    is used to determine if the clip posting data is
                    obsolete.

CBD_POST            Post the availability of clip data.

CMD_READ            Read data from the clipboard for a paste.  Data can be
                    read from anywhere in the clipboard by specifying an
                    offset >0 in the I/O request.

CMD_UPDATE          Indicate that the data provided with a write command
                    is complete and available for subsequent read/pastes.

CMD_WRITE           Write data to the clipboard as a cut.


Exec Functions as Used in This Chapter
--------------------------------------
CloseDevice()       Relinquish use of the clipboard device.  All requests
                    must be complete before closing.

DoIO()              Initiate a command and wait for completion
                    (synchronous request).

GetMsg()            Get next message from a message port.

OpenDevice()        Obtain use of the clipboard device.

SendIO()            Initiate a command and return immediately
                    (asynchronous request).


Exec Support Functions as Used in This Chapter
----------------------------------------------
CreateExtIO()       Create an I/O request structure of type IOClipReq.
                    This structure will be used to communicate commands to
                    the clipboard device.

CreatePort()        Create a signal message port for reply messages from
                    the clipboard device.  Exec will signal a task when a
                    message arrives at the port.

DeleteExtIO()       Delete an I/O request structure created by
                    CreateExtIO().

DeletePort()        Delete the message port created by CreatePort().