About Application Resources

Much of the information that defines the appearance, behavior and functionality of a Symbian OS application is stored in a resource file external to the main body of the program. This is unlike some other programming environments where a single executable contains all the code and information used by the application.

Resource files can have the advantage that information is loaded only when needed. They can be compressed which reduces RAM requirements and they can be localized without needing to recompile the main program.

Resource files are developed as text files written in a Symbian OS-specific resource language. These source files are then compiled into a binary file format that can be loaded and read by programs. The source files can be compiled on their own using the command-line resource builder tool, epocrc, or as part of the standard project building process either from the command line or from within an IDE.

Resource files fulfill two purposes:

• Application user interfaces (APIs) in the C++ application programming framework require that some aspects of an application's layout and behavior, such as the menu, are defined in a resource file.

• Literal strings and other constant data, for example, dialog texts and error messages are stored in resource files. The resource tool chain provides support for localization of these.

The resource compilation process uses a number of file types: