SCIENCE:Fold a piece of paper in half and crease it. Tear the paper along the fold and you have two PDAs, writes Dick Ahlstrom

It is always a challenge around Christmas time to find practical and useful gifts for friends and relations. And given the themes and issues raised in this publication, one should also think in terms of promoting innovative thinking when selecting presents for under the Yuletide tree.

With this in mind, your columnist humbly offers a suggestion that will delight and impress even the most difficult to please person on your Christmas list. And, it fulfills the need to foster innovation and encourage people to become more efficient.

Why not give a PDA, or personal digital assistant as a gift this Christmas? PDAs are a must-have for the busy executive, student or home worker who needs to organise their time better and provide a place to jot down ideas and make notes.

These useful devices can store information, alert you to meetings and appointments, help you plan your day and keep you in touch with your busy life, for example, warning you if your wife's birthday or your anniversary is around the corner.

They hold addresses and phone numbers and allow quick retrieval if you need to make a call. They are lightweight and compact and so are easy to carry about, readily on hand as soon as you need them. And as your repository of information grows, you can add memory to increase the amount of information your PDA can handle.

But what about price, you might argue? The more expensive PDAs can run into hundreds of euro and if you want to combine them with a mobile phone, the cost soars.

Happily my brother Jim has cracked this little problem. He has found a PDA that is so cheap you could afford to give one to a hundred or more of your closest friends this Christmas without having to be the man who broke the bank at Monte Carlo.

All you need is a sheet of A4 paper. Fold this in half and crease it well. Then tear the paper along the fold and voila. You have two PDAs ready for use, one for yourself and one for that special friend.

There is a slightly technical bit that goes along with this PDA model, but it isn't too difficult. You must choose the size that most suits your favoured pocket. Most fold the piece of paper twice more to produce a pda that fits readily into a shirt pocket. Fold once more if you want a smaller but slightly thicker PDA.

The pointer is less of a problem, any pen or pencil will do and which ever implement is chosen then also serves as your data transfer device. Some cut a pencil in quarters to reduce the pointer size for a really compact PDA.

Jim points out that this device has many of the features associated with the much more expensive PDAs, the kind that actually use electricity. Memory is readily expanded with no more than the flick of the wrist once one face of the PDA is filled with data. You simply fold over your PDA to reveal a fresh, unmarked face.

You can also easily marshal your stored information, much the same as you can with an "ordinary" electronic (and much more bulky and heavy) PDA.

This "starter" PDA model offers eight faces for data (16-faces if you choose the smaller "nano" model with the extra fold), so you could use one face for your "to do" items, and then flip to another face for keeping your appointments in order or for a diary of events. Addresses, meanwhile, can be stored on a less readily accessible face as these are not needed as frequently.

The very low cost of this PDA's memory suggests that it be treated as Worm (write-once, read-many) memory, akin to the CD-R or DVD-R formats. Jim argues however that a determined user armed with an eraser or a bottle of correction fluid could easily convert this to a fully rewritable media format as a way to save money.

There is one drawback, the need to renew stored data once you discard an old pda and start a new one. One way to avoid this is to use a full A4 sheet and three folds to deliver a 16-face PDA. This gives you no less than double the memory in almost the same compact space as the eight-face PDA.

Real technophiles might want to consider the more complicated four-fold model which starts with a sheet of A3 but gives you no less than 32 full faces for data. Its use requires a bit more fiddling to reach fresh faces but it does give you all that extra memory space in a PDA that still slips easily into a shirt pocket.

The one thing to remember about Jim's PDA is that it really works, allows you to manage time and information and does most of what you want from an electronic PDA but at virtually zero cost. Go figure.