INT 21 U - DR DOS 5.0+ internal - GET POINTER TO INTERNAL VARIABLE TABLE        
	AX = 4458h
Return: ES:BX -> internal variable table (see #01584,#01585)
	AX = ??? (0B50h for DR DOS 5.0, 0A56h for DR DOS 6.0, 0FE4h for
		  Novell DOS 7)
SeeAlso: AX=4452h


Format of DR DOS 5.0-6.0 internal variable table:
Offset	Size	Description	(Table 01584)
 00h	WORD	???
 02h	WORD	segment of ???
 04h	WORD	offset within DOS data segment of history control structure
		  for COMMAND.COM history buffer (see #01586)
 06h	WORD	offset within DOS data segment of history control structure
		  for application history buffer (see #01586)
 08h	BYTE	initial history state flags (see #01583)
 09h  2 BYTEs	???
 0Bh	WORD	KB of extended memory at startup
 0Dh	BYTE	number of far jump entry points
 0Eh	WORD	segment containing far jumps to DR DOS entry points (see #01587)
 10h	WORD	(only if kernel loaded in HMAsee High Memory Area) offset in HMAsee High Memory Area of first free HMAsee High Memory Area
		  memory block (see #01588) or 0000h if none; segment is FFFFh
 12h	WORD	pointer to segment of environment variables set in CONFIG,
		  or 0000h if already used
---DR DOS 6.0---
 14h	WORD	(only if kernel loaded in HMAsee High Memory Area) offset in HMAsee High Memory Area of first used HMAsee High Memory Area
		memory block (see #01588) or 0000h if none; segment is FFFFh
 16h  8 BYTEs	???
 1Eh	WORD	offset in DOS data segment of full COUNTRY.SYS filename
 20h  8 BYTEs	???
 28h	WORD	offset in DOS data segment of SHARE hook table
 2Ah  2 BYTEs	???
 2Ch	WORD	offset in DOS data segment of far pointer to INT 2F/AX=1000h
		  handler
Notes:	the segment used for the DR DOS 6.0 CONFIG environment variables
	  (excluding COMSPEC, VER and OS) is only useful for programs/drivers
	  called from CONFIG.SYS. The word is set to zero later when the area
	  is copied to the COMMAND.COM environment space.  This allows
	  CONFIG.SYS to pass information to AUTOEXEC.BAT.
	the Novell DOS 7 KEYB uses offsets 10h,14h, and 2Ch in the same was
	  as for DR DOS 6.0, so it is likely that the entire table is the same


Format of Novell DOS 7 internal variable table:
Offset	Size	Description	(Table 01585)
 00h	???
 1Eh	WORD	offset of COUNTRY.SYS filename
 42h 16 DWORDs	pointers to ??? entry points
	???


Format of history control structure:
Offset	Size	Description	(Table 01586)
 00h	WORD	segment of buffer
 02h	WORD	size of buffer in bytes
 04h	WORD	???


Format of kernel entry jump table for DR DOS 5.0-6.0:
Offset	Size	Description	(Table 01587)
 00h  5 BYTEs	far jump to kernel entry point for CP/M(Control Program for Microcomputers) An early operating system for micros based on the 8-bit Intel 8080 CPU (and later the compatible 8085 and Zilog Z80 CPUs).  MSDOS version 1.0 was essentially a clone of CP/M for the Intel 8086. CALL 5
 05h  5 BYTEs	far jump to kernel entry point for INT 20
 0Ah  5 BYTEs	far jump to kernel entry point for INT 21
 0Fh  5 BYTEs	far jump to kernel entry point for INT 22 (RETF)
 14h  5 BYTEs	far jump to kernel entry point for INT 23 (RETF)
 19h  5 BYTEs	far jump to kernel entry point for INT 24
 1Eh  5 BYTEs	far jump to kernel entry point for INT 25
 23h  5 BYTEs	far jump to kernel entry point for INT 26
 28h  5 BYTEs	far jump to kernel entry point for INT 27
 2Dh  5 BYTEs	far jump to kernel entry point for INT 28
 32h  5 BYTEs	far jump to kernel entry point for INT 2A (IRET)
 37h  5 BYTEs	far jump to kernel entry point for INT 2B (IRET)
 3Ch  5 BYTEs	far jump to kernel entry point for INT 2C (IRET)
 41h  5 BYTEs	far jump to kernel entry point for INT 2D (IRET)
 46h  5 BYTEs	far jump to kernel entry point for INT 2E (IRET)
 4Bh  5 BYTEs	far jump to kernel entry point for INT 2F
Notes:	all of these entry points are indirected through this jump table
	  to allow the kernel to be relocated into high memory while leaving
	  the actual entry addresses in low memory for maximum compatibility
	some of these entry points (22h,23h,24h,2Eh,2Fh) are replaced as soon
	  as COMMAND.COM is loaded, and return immediately to the caller, some
	  returning an error code (the original handler for INT 2F returns
	  AL=03h [fail]).


Format of HMAsee High Memory Area Memory Block (DR DOS 6.0 kernel loaded in HMAsee High Memory Area):
Offset	Size	Description	(Table 01588)
 00h	WORD	offset of next HMAsee High Memory Area Memory Block (0000h if last block)
 02h	WORD	size of this block in bytes (at least 10h)
 04h	BYTE	type of HMAsee High Memory Area Memory Block (interpreted by MEM)
		00h system
		01h KEYB
		02h NLSFUNC
		03h SHARE
		04h TaskMAX
		05h COMMAND
 05h	var	TSR(Terminate and Stay Resident) A program which remains in memory after terminating in order to provide services to other programs or the user.  The name comes from the name of the DOS function call used to remain in memory after termination. (or system) code and data. DR DOS TSR(Terminate and Stay Resident) A program which remains in memory after terminating in order to provide services to other programs or the user.  The name comes from the name of the DOS function call used to remain in memory after termination.'s, such as KEYB,
		  hooks interrupts using segment FFFEh instead FFFFh.