PAL and NTSC

Restricting programs to a single mode
Many AMOS Professional programmers may decide to ignore these problems completely, satisfied that their work will not be seen outside of their immediate circle of contacts, let alone outside of their country. However, this is not a professional attitude, and if you have any intention of reaching a wider audience with your programming, there is nothing worse than allowing your work to fall apart before the eyes of an unsuspecting user.

So, if compatibility problems are not to be ignored, they can at least be avoided. This is achieved by adding a simple test at the start of a program, which will warn other users of potential problems, and abort the program if it is run on an incompatible machine.

NTSC
function: identify NTSC or PAL machines
mode=Ntsc

The NTSC function is provided to identify whether or not an NTSC machine is in use, and will return a value of -1 (True) if this is so. Otherwise a value of zero (False) is given, when a PAL machine is identified. The following example gives an idea of its use, and similar routines are essential for professional releases aimed at an international audience:

E> If Ntsc=0
    Print "Sorry, PAL version only!"
    Print "NTSC version coming soon!"
    End
   End If

Dual mode programs
Whereas synchronisation problems can be overcome, the difficulties caused by the two different sized screens causes a bigger problem. The smaller working area of NTSC displays has to be taken into account at the beginning of your program. To open a perfect screen in either display mode, you are recommended to save the screen height and position as global variables, which may be set at the start of a program, as follows:

E> Global YSIZE,YPOSITION
   YSIZE=256 : YPOSITION=49
   If Ntsc
    YSIZE=200 : YPOSITION=55
   End If
   Screen Open 0,320,YSIZE,16,Lowres
   Screen Display 0,,YPOSITION,,

NTSC users can easily provide their PAL cousins with a dormant screen area at the bottom of the display.

To return the complement, PAL users should restrict the size of their menus, activity buttons, dialogue boxes, and similar features, to no more than a quarter of the total screen area.