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. - OS/2 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. DosQFSAttach
	AH = 64h
	BX = 00B6h (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. ordinal)
	CX = 636Ch (magic value "cl")
	DS = user's data segment
	ES:DI -> FSQAttachStruc (see #01749)
Return: CF set on error
	    AX = error code (see #01680 at AH=59h/BX=0000h)
	CF clear if successful
	    AX = 0000h
	    data buffer filled
SeeAlso: AH=64h/CX=636Ch


Format of OS/2 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. FSQAttachStruc:
Offset	Size	Description	(Table 01749)
 00h	DWORDDoubleword; four bytes.	 Commonly used to hold a 32-bit segment:offset or selector:offset address.	reserved
 04h	DWORDDoubleword; four bytes.	 Commonly used to hold a 32-bit segment:offset or selector:offset address.	pointer to the offset of the data buffer length
 08h	DWORDDoubleword; four bytes.	 Commonly used to hold a 32-bit segment:offset or selector:offset address.	pointer to the offset of the data buffer
 0Ch	WORD	FSA Info level
 0Eh	WORD	ordinal index into table
 10h	DWORDDoubleword; four bytes.	 Commonly used to hold a 32-bit segment:offset or selector:offset address.	pointer to the offset of the device name
Notes:	The segment value of the buffer, buffer length, and device
	  name MUST all be the same.  It is defined on entry in the DS
	  register.  The details of each info level are defined in the
	  OS/2 CP Reference.