Even better practice is to use pull-down menus rather than dialogue boxes. Before "releasing" a program, you should simulate an NTSC screen by changing a simple screen variable, and checking that everything appears to be in order.
An examination of the Object Editor and all of the ready-made AMOS Professional HELP programs will show how they adapt themselves to the current display mode automatically!
Certain recent Amiga models have special monitors which are designed to accommodate both systems. For example, the A3000 can emulate both PAL and NTSC, and you should check your Amiga manual for details. As far as AMOS Professional is concerned, the current mode is dictated by the type of screen which occupies the front of the display when the machine is booted. Supposing you have an A3000 in PAL mode, and have set its preferences to NTSC. The Amiga will be in NTSC mode when the Workbench screen is the front screen, but it will return to its default PAL mode as soon as another screen is brought forward.
AMOS Professional relies on the current mode to establish the maximum display size, so if it is run from an NTSC Workbench, it will be in NTSC mode of 200 lines maximum, cycling at 60 hertz. However, if you flip to Workbench by pressing [Amiga]+[A], and start another program which opens a new screen, the A3000 will revert to PAL without informing AMOS Professional. This means that when you return to AMOS Professional, the size of the display will be limited to 200 lines, but the update frequency will be 50 hertz. A hybrid PAL/NTSC mode!
Nothing can prevent this, other than the purchase of a genuine NTSC machine!
International television standard systems
The following lists catalogue the different standard systems adopted in various territories
around the world.
PAL(I)
Gibraltar, Hong Kong, Malvinas, Republic of Ireland, United Kingdom
PAL(B/G/H)
Afghanistan, Algeria, Australia, Bahrain, Bangladesh, Belgium, Bosnia, Brunei, Central African
Republic, Denmark, Equatorial Guinea, Ethiopia, Finland, Germany, Ghana, Greenland, Iceland,
India, Indonesia, Jordan, Kenya, Kuwait, Liberia, Luxembourg, Malaysia, Maldives, Malta,
Mozambique, Netherlands, New Zealand, Nigeria, Norway, Oman, Pakistan, Portugal, Qatar,
Serbia, Seychelles, Sierra Leone, Singapore, Spain, Sri Lanka, Sudan, Swaziland, Sweden,
Switzerland, Tanzania, Thailand, Yemen Arab Republic, Turkey, United Arab Emirates, former
Yugoslavian territories, Zambia.
NTSC(M)
Antigua and Barbuda, Bahamas, Barbados, Belize, Bermuda, Bolivia, Burma, Canada, Chile,
Colombia, Costa Rica, Cuba, Dominican Republic, Ecuador, Guatemala, Haiti, Honduras,
Jamaica, Japan, Kampuchea, Mexico, Micronesia, Nicaragua, Panama, Peru, Philippines, Puerto
Rico, Saint Christopher and Nevis, Saint Lucia, Samoa, South Korea, Surinam, Taiwan, Trinidad
and Tobago, United States of America, Venezuela