Int 21/AH=3Fh

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IFSHLP.SYS - GET ENTRY POINT

AH = 3Fh
BX = file handle for device "IFS$HLP$"
CX = 0008h (size of buffer in bytes)
DS:DX -> buffer for entry point record (see #01415)

Return:
CF clear if successful AX = number of bytes actually read (0 if at EOF before call) CF set on error AX = error code (05h,06h) (see #01680 at AH=59h/BX=0000h)

Program: IFSHLP.SYS is a support driver for Microsoft Windows for Workgroups

See Also: AX=4402h"IFSHLP"

Format of IFSHLP.SYS entry point record: Offset Size Description (Table 01415) 00h 4 BYTEs (call) required signature if called via IOCTL 70h E9h 34h 37h for Windows 3.11 70h E9h 35h 37h for Windows 3.11 (ret) signature 34h 37h 70h EFh (Windows 3.11) (ret) signature 35h 37h 70h EFh (Windows95) 04h DWORD (ret) pointer to FAR call entry point (see #01416)

(Table 01416) Call IFSHLP.SYS entry point with:.

STACK:
WORD function number (00h-0Ch) 00h get ??? data 01h set interrupt intercepts (trap) 02h remove interrupt intercepts (untrap) 03h ??? LPT2 04h ??? LPT1 05h revector INT 2F to trap and remove trap for others 06h set ??? flag 07h clear ??? flag 08h get ??? flag word ---Windows 3.11 only--- 09h ??? 0Ah ??? 0Bh ??? 0Ch get ??? ---if function 00h---

Return:
DX:AX -> ??? data (see #01417) BX destroyed ---if function 01h---.

STACK:
DWORD new intercept (trap) address

Return:
AX = status 0000h successful 0001h failed (already set) DX = 0000h BX destroyed

Note: The trap handler is called with a function number in BX, and the original BX on top of the stack; a null handler must perform a POP BX and an IRET ---if function 02h---

Return:
AX = status 0000h successful 0001h failed (not set) DX = 0000h BX destroyed ---if function 03h,04h---.

STACK:
WORD ???

Return:
AX = 0000h DX = 0000h BX destroyed ---if function 05h--- ???

Return:
BX destroyed ---if function 06h---

Return:
AX = 0001h and DX = 0000h if already set AX,DX unchanged if successful BX destroyed ---if function 07h---

Return:
AX = 0001h and DX = 0000h if not set AX,DX unchanged if successful BX destroyed ---if function 08h---

Return:
DX = 0000h AX = flags

bit 0:
Set/cleared by functions 06h and 07h

bit 1:
Trap is currently set (refer to functions 01h/02h). BX destroyed ---if function 09h---

Return:
AX = status 0000h successful 0001h failed (already called) BX destroyed ---if function 0Ah---.

STACK:
WORD ???. ???

Return:
BX destroyed ---if function 0Bh---

Return:
AX = status 0000h successful 0001h failed (not set) BX destroyed ---if function 0Ch---

Return:
AX = 0000h ES:BX -> ??? data ---if function > 0Ch---

Return:
AX = 0001h DX = 0000h BX destroyed

Format of IFSHLP ??? data: Offset Size Description (Table 01417) 00h DWORD -> DOS Swappable Data Area (see #01687,#01689) 02h WORD ??? offset in DOS data segment? 04h WORD offset in DOS data segment of current-PSP WORD 06h WORD ??? 08h WORD ??? 0Ah WORD ??? 0Ch DWORD -> DOS List of Lists (see #01627) 10h ???

See Also: #01416

Category: Uncatagorized - Int 21h - I

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