THERE seems to be no limit to the miniaturisation of computers, because in the wake of laptops comes pocket-sized computers that allow the user to write on a liquid crystal screen with a special pen and even fax messages.

Personal digital assistants (PDAs), as they are called, can store even scribbles and sketches as images and turn handwriting into type (New Scientist, Vol 138, No 1867).

One of the more attractive qualities of the PDA is its ability to communicate, using either a telephone socket or mobile phone link, and even send electronic "postcards". For example, if you are in a meeting and likely to be delayed, you could write a quick note to your home saying you will be home late.

But there is a catch: Manufacturers aren't agreed on standards and so each of these gadgets will need different software.