Psion Handheld Computers
Psion Organiser I 1984, Organiser II 1986
The early Organisers (the I and II) in 1984 and 1986 were really designed as a sort of database. Calendar events are just items of data, many other things can be minimised to a bit of text identified by some primary key. I did not use my Organiser II as a calendar (a Filofax made a much better job of it) but I did use it to store lots of basic information on everything else. This was in my Army days so it could store parts lists, organisation lists, anything which you really wanted to have handy and it was certainly tidier and more exciting than sheets of paper. It was not the prettiest of devices and its shape made it impossible to carry around in a normal pocket. The basic storage (2K of memory on the I, 8 or 16K on the II) could be supplemented by up to two plug-in memory modules which each could hold a further 256K of data. The internal memory was battery backed (by a single 9v battery) so if your battery went flat (which it did a lot) then you lost the lot. The memory modules were usually EPROM (this means they needed electrical current to write the data but then retained that data even when switched off) so were a safe storage location. Writing an EPROM hammered the battery making an external power supply just about essential. Data could also not be deleted. If you modified a record then the old record was flagged as deleted and a new record saved. The space of the deleted record was lost forever. Actually, not quite true. An EPROM can be entirely erased by UV light, either an EPROM eraser or just put the EPROM on the windowsill on a sunny day for hours. Of course, that lost everything so the usual technique was to only store to one module then write the active records to the second module, erase the first and wait until the second one was full. And remember your power supply as no battery in existence could write all those records to the second module!
The other, obvious difference between the I and the II was the display, the I had an LCD display of one line of 16 characters, the II had two lines of 16 characters. The II also had a connection port able to communicate with other computers or add-on devices.
Other details, they had a horrible little keyboard, calculator keys you could live with but whoever thought putting the keys in alphabetical order rather than QWERTY needed to be shot! On the positive side, they were incredibly robust, almost unbreakable. Any you see today will almost certainly still be working. These were taken up by some of the supermarkets (Marks and Spencer for one) where they were used for stock-taking applications. You will see them with custom keypads of perhaps 10 or 15 keys. These are very cheap to obtain though of no use whatsoever!