)
Values for PC-IPC command code:
 01h "IPC_CMND_INQUIRE"	 inquire current status
	set status field, writes WORD to data buffer containing free
	  message space in bytes, and sets the "size" field to the
	  number of messages waiting
 02h "IPC_CMND_ENABLE"	reenable PC-IPC
	ignored unless called with the same ID that disabled PC-IPC
 03h "IPC_CMND_DISABLE" disable PC-IPC
 04h "IPC_CMND_INSTALL" reset PC-IPC
 06h "IPC_CMND_RDATA"	read data
	returns first message in data buffer, sets "size" to message length
	  and "to ID" field to sender's ID
	if no messages available, bit 4 of status is cleared and "size" is
	  set to zero
 07h "IPC_CMND_SDATA"	send data
 08h "IPC_CMND_REQID"	require user ID
	create a new recognized ID and return in "caller's ID" field
 09h "IPC_CMND_DELID"	cancel user ID
	delete caller's ID from pool of recognized IDs
 0Ah "IPC_CMND_RDATAW"	read data, wait if no messages available
 0Bh "IPC_CMND_VERS"	get PC-IPC version
	string representing version returned in data buffer, "size" field
	  set to length of string