Environment > Distributing IDL Applications > Callable IDL Applications > Limitations of Runtime Applications

# Limitations of Runtime Applications

IDL applications that run without an IDL development license — whether native IDL or Callable IDL — do not have access to the IDL compiler and thus cannot compile IDL source code from `.pro` files. As a result, operations that require the compiler will not execute when a development license is not present. In addition, if you are writing an IDL application to be distributed to users who do not have a development IDL license, you should be aware of the following limitations.

Note: Since runtime applications do not provide access to the IDL command line, startup files are not executed.

- Because the ON_ERROR procedure has the potential to force the IDL interpreter into an idle state when an error is encountered, use the CATCH procedure instead if your application will be distributed to users without a development IDL license.
- When a SAVE file is executed with a runtime or embedded license, IDL’s current working directory will be the directory that contains the SAVE file.
- Support for the IDL help system is not included in a runtime distribution by default. This means that applications that use the ONLINE_HELP procedure to display IDL help topics will fail unless you explicitly include the required support. If you use the MAKE_RT procedure to create a runtime distribution, you can use the IDL_HELP keyword to include the necessary files. Support for the IDL Assistant help viewer (IDL’s standard help viewer for releases 6.2 thorugh 6.4) is not included in a runtime distribution by default. If your application uses an IDL Assistant help system (that is, if it includes a `.adp` file), you will need to explicitly include the IDL Assistant help viewer. If you use the MAKE_RT procedure to create a runtime distribution, you can use the IDL_ASSISTANT keyword to include the necessary files.