INT 21,0 - Program Terminate

	AH = 00
	CS = PSP segment address

	returns nothing

	- restores the terminate, Ctrl-Break, and critical error
	  exit addresses, flushes all buffers, frees memory
	  and returns to DOS via the termination handler address
	- does not close FCBs
	- this function is no longer recommended, but can be used by
	  version of DOS before 2.0, see  INT 21,4C  and  INT 20