Changing Interrupt Vector Table (Create your own interrupt!)
 Author: InternetNightmare

Another thing I want to write tutorial is about changing interrupts. There are two ways you can do that using DOS interrupts and modifying interrupt vector table directly. Both ways are pretty simple, you need to know these DOS interrupts:

It’s pretty simple, just take a look at the sample code here.

The other way to make your own interrupt is to modify interrupt vector table directly. It’s mapped from 0000:0000 to 0000:0400h in memory. The structure is very simple:

So getting interrupt offset is:
mov ax, [intnum*4]

 And segment:
mov ax [intnum*4+2]

Setting:
mov ax, [intnum*4] ; offset
mov ax [intnum*4+2] ; segment

Well and how to call the interrupt, I think we all know:
int intnum

Everything is pretty simple. NASM soruce code:

DOS interrupt version – here
Direct modifiying of intvec table - here