Interrupts

    While a calculation is in progress, you can generate the SIGINT
    signal, and the calculator will catch it.  At appropriate points
    within a calculation, the calculator will check that the signal
    has been given, and will abort the calculation cleanly.  If the
    calculator is in the middle of a large calculation, it might be
    a while before the interrupt has an effect.

    You can generate the SIGINT signal multiple times if necessary,
    and each time the calculator will abort the calculation at a more
    risky place within the calculation.	 Each new interrupt prints a
    message of the form:

	    [Abort level n]

    where n ranges from 1 to 3.	 For n equal to 1, the calculator will
    abort calculations at the next statement boundary.	For n equal to 2,
    the calculator will abort calculations at the next opcode boundary.
    For n equal to 3, the calculator will abort calculations at the next
    lowest level arithmetic operation boundary.

    If a final interrupt is given when n is 3, the calculator will
    immediately abort the current calculation and longjmp back to the
    top level command level.  Doing this may result in corrupted data
    structures and unpredictable future behavior, and so should only
    be done as a last resort.  You are advised to quit the calculator
    after this has been done.

## Copyright (C) 1999  Landon Curt Noll
##
## Calc is open software; you can redistribute it and/or modify it under
## the terms of the version 2.1 of the GNU Lesser General Public License
## as published by the Free Software Foundation.
##
## Calc is distributed in the hope that it will be useful, but WITHOUT
## ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
## or FITNESS FOR A PARTICULAR PURPOSE.	 See the GNU Lesser General
## Public License for more details.
##
## A copy of version 2.1 of the GNU Lesser General Public License is
## distributed with calc under the filename COPYING-LGPL.  You should have
## received a copy with calc; if not, write to Free Software Foundation, Inc.
## 59 Temple Place, Suite 330, Boston, MA  02111-1307, USA.
##
## @(#) $Revision: 29.1 $
## @(#) $Id: interrupt,v 29.1 1999/12/14 09:15:54 chongo Exp $
## @(#) $Source: /usr/local/src/cmd/calc/help/RCS/interrupt,v $
##
## Under source code control:	1991/07/21 04:37:21
## File existed as early as:	1991
##
## chongo <was here> /\oo/\	http://reality.sgi.com/chongo/
## Share and enjoy!  :-)	http://reality.sgi.com/chongo/tech/comp/calc/
