INT 21 U - DR-DOS 5.0+ internal - GET POINTER TO TABLE OF ???
AX = 4458h
Return: ES:BX -> internal table (see below)
AX = ??? (0B50h for DR-DOS 5.0, 0A56h for DR-DOS 6.0)

Format of internal table:
Offset  Size    Description
00h    DWORD   pointer to ???
04h  7 BYTEs   ???
0Bh    WORD    K 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 below)
10h    WORD    ???
12h    WORD    pointer to segment of environment variables set in CONFIG,
or 0000h if already used (DR-DOS 6.0 only)
14h    ???     ???
Note:   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 and the area
lost.

Format of jump table for DR-DOS 5.0-6.0:
Offset  Size    Description
00h  5 BYTEs   far jump to entry point corresponding to CP/M CALL 5
05h  5 BYTEs   far jump to entry point corresponding to INT 20
0Ah  5 BYTEs   far jump to entry point corresponding to INT 21
0Fh  5 BYTEs   far jump to entry point corresponding to ???
14h  5 BYTEs   far jump to entry point corresponding to ???
19h  5 BYTEs   far jump to entry point corresponding to ???
1Eh  5 BYTEs   far jump to entry point corresponding to ???
23h  5 BYTEs   far jump to entry point corresponding to ???
28h  5 BYTEs   far jump to entry point corresponding to ???
2Dh  5 BYTEs   far jump to entry point corresponding to ???
32h  5 BYTEs   far jump to entry point corresponding to ??? (IRET)
37h  5 BYTEs   far jump to entry point corresponding to ??? (IRET)
3Ch  5 BYTEs   far jump to entry point corresponding to ??? (IRET)
41h  5 BYTEs   far jump to entry point corresponding to ??? (IRET)
46h  5 BYTEs   far jump to entry point corresponding to ??? (IRET)
4Bh  5 BYTEs   far jump to entry point corresponding to ???

See also: 214452

214458 - DR-DOS 5.0+ internal - GET POINTER TO TABLE OF ???