Int 21H [1.0] Function 25H (37) Set interrupt vector

Initializes a CPU interrupt vector to point to an interrupt handling routine.

Call with:

AH = 25H

AL = interrupt number

DS:DX = segment:offset of interrupt handling routine

Returns:

Nothing

Notes:

This function should be used in preference to direct editing of the interrupt-vector table by well-behaved applications.

Before an interrupt vector is modified, its original value should be obtained with Int 21H Function 35H and saved, so that it can be restored using this function before program termination.

Example:

Install a new interrupt handler, named zdiv, for "divide by zero" CPU exceptions.

.

.

.

mov ah,25h ; function number

mov al,0 ; interrupt number

mov dx,seg zdiv ; address of handler

mov ds,dx

mov dx,offset zdiv

int 21h ; transfer to MS-DOS

.

.

.

zdiv: ; int 00h handler

iret ; (does nothing)