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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)
See Also: 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 HMA) offset in HMA of first free HMA 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 HMA) offset in HMA of first used HMA 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 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 01588) 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.
Category: Other Operating Systems - Int 21h - D
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