Calling BIOS Interrupt routine

[Privida]

Hi all,
I want to call BIOS Interrupt routine from VB
how can I use API to do that ?
I use Windows 2000 and VB 6.

[Yonatan]

You will have to use ASM code to do that.
The code is:

int <interrupt number>
ret

You can use a CallWindowProc trick to do this in VB.
This passes 4 parameters to the function as well, so the 'ret' instruction has to be changed to fix the stack alignment thingie:

int <interrupt number>
ret 0010

And in VB:

Option Explicit

Public Declare Function CallWindowProc Lib "user32" Alias "CallWindowProcA" (ByVal lpPrevWndFunc As Long, ByVal hWnd As Long, ByVal Msg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long

Sub Main()
    Dim ASMCode(0 To 4) As Byte
    
    ' int <interrupt number> = CD <interrupt number>
    ASMCode(0) = &HCD
    ASMCode(1) = &H3 ' Testing: Interrupt 3h (debug break)
    
    ' ret 0010 = C2 10 00
    ASMCode(2) = &HC2
    ASMCode(3) = &H8
    ASMCode(4) = &H0
    
    Call CallWindowProc(VarPtr(ASMCode(0)), 0, 0, 0, 0)
End Sub

This will call interrupt 3h. You can change ASMCode(1) to the interrupt number you need.

[Privida]

Thank's Yonatan.

Some Interrupt have sub function dan return value
ie. calling int 1AH, function 0 (read clock)
returns cx= high word count
dx= low word count
al=0

what is the code ?

[Yonatan]

That specific interrupt might work in DOS (16-bit), but definitely not in a Windows program...
Interrupts are very rarely used in Win32 programs, not to mention VB programs.

In DOS, you can use this code:

xor ax, ax
int 1Ah

push cx
push dx
call SomeFunctionWhichDealsWithCxAndDx