Example 1:
 The first example is a very simple program that demonstrates the skeleton of
 a program based on BETATRON.
 The program creates a world 62x52 tiles and then lets the user scroll the view
 window in that world. The program takes as an argument the desired video mode
 which can be 0 (gmMODEX320x200) ,for modex 320x200, or any supported VESA 2.00
 video mode number.
 For example:
     C:\> ex1 257
 will try to use 640x480x256 VESA 2.00 video mode.
 To see VESA 2.00 modes your video card must support VESA 2.00 or you must
 have a VBE2 driver such as UNIVBE.

 Notice the use of exitaction(). This action funtion is called in every frame
 by TOworld::animate(). Notice how this function informs animate() to return
 by setting the 'exitbit' field of its owner TOworld object to 1.

 The code should be self-explanatory because of all those comments.
 However you may wonder what is CHECK(). CHECK() is a macro that takes a
 single argument.  If that argument is negative then CHECK() displays an
 error message and calls 'exit(1)' else it does nothing. CHECK() is designed
 to be used with all BETATRON functions that return a negative number as
 an error code. There are also some other BETATRON functions that return
 FALSE (0) as failure and TRUE as success. CHECK() can't be used with the
 latter ones.

 You should always use CHECK() or check yourself what a function returns
 because in many cases you can't continue if a function fails.
 For example TOworld::animate() cannot be succesfully executed if
 TOworld::initmode() or TOworld::setmode() fail.

 The order in which the various methods are called is important. This example
 demonstrates an apropriate order that you should follow.