Example 1b:
 Three new issues are examined in this improved version of example 1.

First instead of having the user supply the desired mode as an argument
in the command line, we query the BETATRON vesa system to find out what
modes are supported. To do that we first have to call pl_initvesa() and
then pl_getmodes(). pl_getmodes() fills an array with the supported modes
and returns the number of records in this array. So we let the user choose
the mode.

The second thing is the call of pl_saveVESAstate() which saves the hardware
state of the VESA mode in an internal buffer so it can be later restored
by pl_restoreVESAstate(). pl_saveVESAstate() must be called after the desired
mode has been set with TOworld::setmode(). There are several cases (especially
when your program is running under windows 95 in a dos box) in which the video
mode and the view is corrupted. You should always give the user the opportunity
to restore the view and the VESA state. In this example the user can do so by
pressing 'R'. Take a look at exitaction().

Finally we use the hardware keyboard handler of BETATRON which can detect
multiple key presses. We set up the keyboard handler by calling
pl_installkeys() and then use pl_testkey() to check if a key is down.
Please not that when using the keyboard handler of BETATRON you can not use
standard BIOS functions to get input from the keyboard.