>># 
>># Copyright 1990, 1991 by the Massachusetts Institute of Technology and
>># UniSoft Group Limited.
>># 
>># Permission to use, copy, modify, distribute, and sell this software and
>># its documentation for any purpose is hereby granted without fee,
>># provided that the above copyright notice appear in all copies and that
>># both that copyright notice and this permission notice appear in
>># supporting documentation, and that the names of MIT and UniSoft not be
>># used in advertising or publicity pertaining to distribution of the
>># software without specific, written prior permission.  MIT and UniSoft
>># make no representations about the suitability of this software for any
>># purpose.  It is provided "as is" without express or implied warranty.
>># 
>># $XConsortium: bll.m,v 1.6 92/06/11 17:11:26 rws Exp $
>># 
>>#
>>TITLE XBell CH07
>>ASSERTION D XBell-1
If it is possible to ring a bell on the display: When the
percent argument is nonnegative, then the volume at which
the bell rings, where base is the base volume of the bell,
is base - [(base*percent)/100]+ percent.
>>STRATEGY
Try out some nonnegative values.
>>ASSERTION D XBell-2
If it is possible to ring a bell on the display: When the
percent argument is negative, then the volume at which the
bell rings, where base is the base volume of the bell, is
base+ [(base*percent)/100].
>>STRATEGY
Try out some negative values.
>>ASSERTION A XBell-3
When the value for the percent argument is not in the range
-100 to 100 inclusive, then a BadValue error occurs.
>>STRATEGY
Call XBell with invalid percent argument.
Verify that BadValue error occurs.
