INT 16 U - PCIBM PC Tools v6.0+ PCRUN API(Application Program[ming] Interface) The defined set of calls which a program may make to interact with or request services of the operating system or environment under which it is running.  Because the inputs and outputs of the calls are well-defined, a program using the API can continue using the identical calls even if the internal organization of the program providing the API changes. - ???
	AX = FFDDh
	BX = 000Bh
	???
Return: CX = 5555h if PCRUN active
	DX = 5555h
Note:	also clears flag set by AX=FFDDh/BX=000Ah