The Series 5 uses language extensions provided in separate DLLs written specially for OPL support. These DLLs have the file extension OPX (OPL Extensions).

What is an OPX?

According to the Symbian website:

An OPX is an Symbian OS DLL containing functions written in C++. These functions can be called from OPL as efficiently as its language keywords. This mechanism gives OPL access to the full capabilities of the underlying Symbian OS operating system, meaning that the language can be extended as required.

John McAleely (see below) gives a good definition of what OPXs are, he writes,

"OPX's are a mechanism for developers to extend the OPL language built into every Psion Series 5 (And GeoFox One) with new features that Psion did not initially provide. Authors use them to access more sophisticated features in the built in database, write to Agenda files and many others. They offer several advantages - they are easy to use (they work just like built in OPL commands) and relatively straightforward to create. They can also be shared among applications, saving users disk space and authors time - by re-using already debugged code."

It is not within the scope of this page (or my current programming ability!) to cover how to develop OPXs yourself, as it requires knowledge of the C++ language.

If you require details of how to do this, you should obtain a copy of the EPOC32 C++ Software Development Kit (SDK).

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'Official' list of OPXs available

www.mcaleely.com/psion/OPX/

John McAleely is the keeper of what many regard as the 'Official' OPX list.

As he writes, "this page is intended as a resource for EPOC OPL developers. It is a list of all the language extensions, known as OPX's, that I am currently aware of."

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Symbian Project OPX

www.symbian.com/developer/downloads/project_opx.html

The aim of Project OPX is to efficiently achieve a comprehensive suite of OPX facilities. The Symbian website gives links to Beta OPXs (OPXs that are being tested before full release), Released OPXs (Symbian written OPXs that are available for you to use), and Third Party OPXs (OPXs written by third parties).

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Installing OPXs

McAleely also wrote an article on installing OPXs on your Psion device: www.mcaleely.com/psion/OPX/OPXInstall.html

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OPX for developers

McAleely also wrote an article for developers, about distributing OPXs with the same filename as another OPX. You can find this article at: www.mcaleely.com/psion/OPX/version.html

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Leigh Edwards on OPX

Leigh Edwards' book Programming Psion Computers (see below) has a section on OPXs (pages 14-8 to 14-10).

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Eric Lindsay on OPX

Eric Lindsay has a good section on his website about OPX at http://www.ericlindsay.com/epoc/mopx5.htm

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