INT 21 U - OS/2 v2.1+ Virtual DOS MachineA special type of virtual machine provided by OS/2 version 2.0, in which a copy of MS-DOS or an MS-DOS compatible operating system (or even an incompatible 8086 operating system) is run and appears to have full control of the system.  See also Virtual Machine, INT 21h Function 64h. - UNLOAD DOSKRNL SYMBOLS & LOAD PROGR
	AH = 64h
	DX = 0006h (function number)
	CX = 636Ch (magic value, "cl")
	BX = 0000h (indicates special request)
	ES:DI -> ASCIZA NUL-terminated ASCII string.	The ASCIZ string "ABC" consists of the four bytes 41h, 42h, 43h, and 00h.  Unless otherwise specified, maximum lengths given in the interrupt list do not include the terminating NUL. filespec
	DS = base address for loading
Notes:	if CX is not 636Ch on entry, INT 21/AH=6Ch is invoked, because a bug
	  in OS/2 1.x FAPI erroneously called AH=64h instead of AH=6Ch
	this function is only supported by the kernel debugging version of
	  OS2KRNL