title: How do I use DOS interrupt 21h/AH=25h (set interrupt vector)?
body: <p>I prompt the user for input:</p>
  
  <pre><code>mov ah, 0Ah
  mov dx, OFFSET buffer
  int 21h
  </code></pre>
  
  <p>My assignment tells me that ctrl-c should "abort the program with an appropriate error message".</p>
  
  <p>I was told that int 23h is called whenever ctrl-c is called or detected. Apparently I can register my own interrupt handler via int 21h / ah=25h. </p>
  
  <p>But I don't know how to make an interrupt handler, nor do I know where this is supposed to go in my code. Assistance would be appreciated, thank you in advance.</p>