Re: INT problem

Daniel Tarbuck (tarbuck@ganymede.futurewest.ca) Sat, 21 Oct 2000 23:34:17 -0700 (PDT) 

Date: Sat, 21 Oct 2000 23:34:17 -0700 (PDT)
From: Daniel Tarbuck <tarbuck@ganymede.futurewest.ca>
Subject: Re: INT problem




The IRET instruction is executed by the interrupt 
handler.  INT   21H  actually loads a new value
into the IP and executes code somewhere else in
memory (DOS code).  The DOS code ends with an
IRET instruction which returns execution to your
code, just after the INT instruction.



Daniel Tarbuck


On Sat, 21 Oct 2000, Yiu Simon wrote:

> I have a little question.  On page 8 of the note "The
> 80386SX Processor Bus and Real-Mode Instruction Set",
> it says the processor will push the flag register, CS
> and IP when an interrupt occurs, use IRET instruction
> to pop the IP, CS and flags register.  However, on the
> subrountin printc of the example on page 9, after int
> 21h, iret is not called.  Then, wouldn't pop dx will
> pop the content of IP previously stored to dx, pop ax
> will pop the content of CS previously stored to ax,
> and ret will pop the content of the flag register
> previously stored to IP?  Thanks in advance.
> 
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