signal SIGIO

[Ray Ward]

I assume you are referring to the SIGIOT signal, and that you have set up
a signal handler for this signal, and that you are now wondering under
what circumstances will this SIGIOT signal be generated.  ("when we requested
signal SIGIO" is a little confusing)

You did not mention what hardware or system software you are using.
According to the System V Interface Definition, the SIGIOT signal's
meaning is implementation dependent:  it may mean one thing on Company A's
machine and quite a different thing on Company B's.  You should look up
signal(BA_OS) or signal(S) or whatever designates your local man pages
for system calls, or call your manufacturer if you don't have on-line 
man pages.

The action and meaning of interrupts is a function of the hardware and
the operating system.  It is not fundamentally a part of the C language,
although some allowance for basic signals is in ANSI C (see section 4.7).
You will notice that SIGIOT is not described in the ANSI C definition.
A better place to post your questions concerning signals might be
comp.unix.questions or comp.unix.xenix or some newsgroup that is more
closely related to your hardware/operating system.
-- 
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Ray Ward                                          Email:  uunet!ctbilbo!ray  
Voice:  (214) 991-8338x226, (800) 331-7032        Fax  :  (214) 991-8968     
=-=-=-=-  There _are_ simple answers, just no _easy_ ones. -- R.R. -=-=-=-=