Copyright: Copyright will automatically protect the original aspects of the software. In some countries (Canada, China, Russia, US) registration of software copyright is highly recommended. Copyright grants automatic protection in a lot of countries internationally based on their membership to an international convention on copyright protection (this is the Berne Convention. It has 179 members). So in practice you get almost full international protection. Copyright protection in countries that are not a member to this convention depends on their national laws and national legal requirements (since copyright laws remain linked to a specific country).
Trade Secret: Trade secrets grant international protection in theory, but in practice protection may vary per country.
Patent: You can file a national, European or international patent application, depending on your market objectives. Be aware that some countries are more flexible in protecting software patents than others.