Int 21 Fn 4458 U - Dr Dos 5.0+ Internal - Get Pointer To Internal Variab [O]
AX = 4458h
Return: ES:BX -> internal variable table (see #1270,#1271)
AX = ??? (0B50h for DR DOS 5.0, 0A56h for DR DOS 6.0, 0FE4h for
Novell DOS 7)
See Also: AX=4452h
Format of DR DOS 5.0-6.0 internal variable table:
Offset Size Description (Table 1270)
00h WORD ???
02h WORD segment of ???
04h WORD offset within DOS data segment of history control structure
for COMMAND.COM history buffer (see #1272)
06h WORD offset within DOS data segment of history control structure
for application history buffer (see #1272)
08h BYTE initial history state flags (see #1269)
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 #1273)
10h WORD (only if kernel loaded in HMA) offset in HMA of first free HMA
memory block (see #1274) 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 HMA) offset in HMA of first used HMA
memory block (see #1274) 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 1271)
00h ???
1Eh WORD offset of COUNTRY.SYS filename
42h 16 DWORDs pointers to ??? entry points
???
Format of history control structure:
Offset Size Description (Table 1272)
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 1273)
00h 5 BYTEs far jump to kernel entry point for CP/M 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 HMA Memory Block (DR DOS 6.0 kernel loaded in HMA):
Offset Size Description (Table 1274)
00h WORD offset of next HMA Memory Block (0000h if last block)
02h WORD size of this block in bytes (at least 10h)
04h BYTE type of HMA Memory Block (interpreted by MEM)
00h system
01h KEYB
02h NLSFUNC
03h SHARE
04h TaskMAX
05h COMMAND
05h var TSR (or system) code and data. DR DOS TSR's, such as KEYB,
hooks interrupts using segment FFFEh instead FFFFh.