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A look at some of the unusual aspects of the EIKON graphical interface from Psion PLC in the United Kingdom, first introduced in 1997. E&OE.



Psion’s EPOC palmtop operating system – now Symbian OS – is a microkernel operating system and thus can support different graphical interfaces. EPOC releases 3 to 5 had a graphical interface called EIKON (Greek for image) which is illustrated here. Symbian OS 6 had a heavily modified EIKON, but later releases had new, competing graphical interfaces. The EIKON interface itself was split into separate components, including a window server and a widget set.

The screenshots on this page are from a Psion Revo Plus palmtop running EPOC32 release 5. There is little difference between the various releases and Psion models, however.


Due to being targeted at pocket devices, most EIKON software runs full-screen and as such, EIKON does not have a desktop of any kind. The shell task cannot be closed, and processes cannot be hidden by the user, so the minimum state of the system is to have the shell taking up the full screen:

The above image also illustrates some conventions of EIKON software. Most applications bear a toolbar down the right side of the screen, containing the active task title, a column of buttons, and the clock. The task title, when tapped or clicked, brings up the task list, but the caption may be freely set to any text. Customarily it is the document title or process name, but a game could show the high score or level instead.


To save screen space, the menu bar is opened on demand the same as with Palm OS. Perhaps unique amongst all graphical interfaces, the menu bar remains open when you switch process:

Two programs both visible with open menus

Normally both menus would not be visible simultaneously, because most EIKON programs run full-screen and the top-most process would have a main window that covers over those of lower processes. In the case of the example above, the main window has been hidden for effect.

Different graphical interfaces take different views on menus. In Mac OS prior to X, menus never had scroll bars, but all menu types were of identical appearance. Starting with Mac OS X, combo boxes alone now feature scroll bars. Windows has always treated pop-up menus differently to pull-down menus; the former take the form of floating list boxes and may possess scroll bars, whereas pull-down menus have very poor Mac-like slide scrolling.

EIKON software typically differentiates pull-down and pop-up menus only in terms of font and font size; both types of menu automatically gain a scroll bar as necessary:

Pop-up menus function the same, but in most cases use smaller type, and are not drawn with space to accommodate tick marks:

Pop-up menus created using the OPL environment appear the same as regular pull-down menus and support keyboard shortcuts, separators, and tick and bullet marks, but do not support horizontal scrolling.


Unlike most graphical interfaces, dialog boxes in EIKON do not visually indicate the default button in a dialog box. Dialog boxes which contain an OK button will have that button as the default, but Yes/No dialog boxes do not have a default: pressing enter has no effect. The following two screenshots show a typical OK/Cancel dialog box and a typical Yes/No dialog box. There is no visual indication that you should press enter for OK in one, but Y for Yes in the other.

Both styles of dialog box can be cancelled by pressing escape.

Psion chose not to use underlined accelerators for dialog boxes. All controls except buttons in a dialog box are aligned vertically and selected using the up and down arrow keys. To increase the capacity of a dialog box, tabs are introduced. Buttons, however, are not accessible via the arrow keys and instead have keyboard shortcuts indicated below them in small text:



After watching a tip about how Mac OS X supports text zoom in certain applications, I was reminded of how EIKON introduced a concept of display zoom in 1997. Implementation was arbitrary and left to the individual developer to design. Many of Psion’s own applications supported zoom. The Sketch drawing program used it to cycle between three zoom levels, and the file manager used it to toggle icon size:

The Jotter program also made use of zooming, which scales not just the text, but embedded objects as well:

At least one game – Mr Matt – makes use of zoom to scale the playfield:


The majority of the EIKON user interface is relatively mundane. Scrollbar buttons are at the same end as on the Amiga and, much later on, the Macintosh. Like Mac OS X, windows also have shadows. But unlike the Macintosh, where shadows are simply negative glow that floats in the air around the window, shadows in EIKON take vertical window distance into account. The shadows are cast by windows onto other windows, with the shadow size being drawn according to the relative height of the window casting the shadow. Shadow intensity, however, remains fixed.

The effect is rather pleasing.

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