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                    is used to determine if the clip posting data is
                    obsolete.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().