Hi Gaurav,
SIGNAL : One kind of IPC.
HARDWARE INTERRUPT: Also refered to as asynchronous interrupts and are generated by hardware devices at arbitrary times with respect to the CPU clock signals.
SOFTWARE INTERRUPT: Also refered to as synchronous interrupts. These are produced by the CPU control unit while executing instructions. The control unit issues them only after terminating the execution of an instruction (eg: exceptions, trap etc).
On 4/10/07, Rajat Jain <rajat.noida.india@xxxxxxxxx> wrote:
> Hi,
>
> I am trying to understand the difference between terms used in Unix like
> harwdare interrupts,signal, software interrupts. I am totally confused be
> means of these terms. Please explain me the meaning of each term (preferably
> along with an example). I also read in one of Richard Steven's book that
> signals are software interrupts. Is this true? Isn't signals are means for
> an OS to report something to the user process and may be initiated by a
> software interrupt or a hardware interrupt? One more thing, When we use term
> interrupt, is this mean hardware interrupt or software interrupt?
>
Hi Gaurav,
SIGNAL: is a mechanism used for IPC (Inter Process Communication) ...
i.e. communication between processes. These have nothing to do with
hardware, and are entirely related to software (though it may be that
a hardware interrupt RESULTS in a signal being sent to a process)
HARDWARE INTERRUPT: is generated from the hardware. The CPU interrupts
what it is currently doing, and service the interrupt by executing the
corresponding Interuupt service routine.
SOFTWARE INTERRUPT: is similar to hardware interrupt but is generated
from the software. For eg. an exception caused by the software (dision
by zero for instance) or a system call from user land (in which case
the system call handler is executed)
Thanks,
Rajat
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