1.2. Implementation The Regina Rexx Interpreter is implemented as a library suitable for linking into third-party applications. Access to Regina from third-party applications is via the Regina API, which is consistent with the IBM’s REXX SAA API. This API is implemented on most other Rexx interpreters. The library containing Regina is available either as a static library or as a dynamically loadable library. The only functional difference between the two libraries is that the ability to dynamically load Rexx external function packages via the built-in function; RxFuncAdd, is only available with the dynamically loadable library. The Regina distribution also includes a front end to the Regina library, to enable the execution of Rexx programs directly from the command line. The command line referred to here relates to the a Unix shell, an OS/2 or DOS command window or a Windows NT/95 command prompt.