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Does Size Matter? Towards a methodology for choosing the size of new devices Alistair D N Edwards Department of Computer Science University of York Heslington York YO10 5DD 1. Introduction There was a time when there was a simple correlation between the power1 of a computer and its size. This is rapidly becoming no longer true; with the continuing validity of Moore’s Law we are almost at a stage whereby as much power as you might desire is available in packages as small as you might choose. That being the case, the size that a designer will choose to make any device will be governed almost entirely by human factors. In anticipation, this paper explores that situation. 2. History It was once the case that if you wanted to do large-scale intensive computing, such as modelling the weather system, then you bought a supercomputer that filled a room. However, if you wanted portability, then you accepted that that you would have limited memory and a slow processor. This is no longer the case. We are almost at the point where it will be possible to have as much computing power as you want in as small a package as you might desire. In that circumstance other factors will dictate what size of device the designer will choose, and most of those factors relate to human characteristics, such as ergonomics. The objective of this paper is to support designers in thinking about matters of size and to stimulate new approaches to product design. The objective is not to speculate on new applications of technology, as such, not to add to the speculation about how convenient life will be when the computer in your fridge can talk to the computer in your phone. The paper does not present any research results and most of the points may seem obvious if you think about them – the objective is to make the reader think about them. 3. Assumptions There are a number of assumptions that should be made clear before the discussion proceeds. One is that speech input will be an option for all devices. The hardware required for speech is very small (a microphone) – and we are assuming that computing power (to perform speech recognition) is not in short supply. Hence, speech input would

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Throughout this paper the term ‘power’ is used in a loose manner to refer to computation speed and memory capacity.

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be an option for any of the devices discussed. In practice there may be other limitations as to its usefulness. Even the best speech recognition is less than 100% accurate, so that feedback is generally required so that the user can confirm correctness. Hence, output limitations may dictate whether speech input is practical. Furthermore we can assume that devices can be connected together. Wireless links are possible on even the smallest of devices. So, in the discussion below it may be suggested, for instance, that smallness constrains input to a particular appliance. We are aware that this limitation could be overcome by the (wireless) connection of a keyboard, but we will assume that this would be an exceptional circumstance and that for day-to-day usage the keyboard would not be available. By extension we can assume that everything is on the internet. Each device will be capable of connection to others, and hence ultimately to any computer on the net. As well as assuming that it will soon be possible to pack as much power as we may want into as small a package, we can presuppose that cost will not be a factor, that small devices will be just as inexpensive as large ones. As new uses are found for small devices this will become increasingly true due to economies of scale in manufacturing. 4. Sizes For the purposes of this paper we will consider the following classification of devices. Clearly the list is not comprehensive and it is possible to identify examples that will fit in gaps between these categories. Miniature A miniature device is so small that it is almost invisible. It is intended to be entirely portable. It might even be surgically implanted in the body. An example would be a hearing aid. Modern aids are more than just sound amplifiers. They comprise digital signal processors which can process the sounds input to enhance the presentation of the signal over the background noise. Users very much prefer that the aid should not be visible. So, ideally it should be small enough to be contained entirely within the ear canal and not be visible externally. Interaction with such a device is minimal. Some might have one or two buttons for input and one or two LEDs for output. Watch The modern watch is worn on the wrist in order to be not just portable, but very readily accessible. Once it was possible to make a timepiece small enough to be worn in this way, it came out of the fob pocket and was strapped to the wrist. That says something about the importance that we attach to time: we want to know it frequently, quickly and accurately. But now we can consider a watch as being a small device with a screen on which we can display a variety of different items and forms of information (possibly including the time). Interaction is limited. A small number of (small) buttons is practical – perhaps four or so. (Watches do exist with a larger number of buttons, comprising calculators, for instance, but they are not easy to use and generally confined to users with a particular need for that kind of device). Does Size Matter? (1.0)

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Phone The mobile phone is an interesting example of size. There is a desire to make the phone as small as possible. Originally this was a selling point in terms of portability, but once a convenient pocket size was attained manufactures tried to go still further, making it a point of fashion. On the other hand, what is possible is constrained by some basic ergonomics. The average distance between the ear and the mouth constrains the size and the shape of most phones. There is some flexibility thanks to the sensitivity of modern microphones. In other words, the phone may be so small that when held to the ear the microphone is quite far from the mouth and yet it picks up the speech. The second limitation on size is the need to dial numbers – and enter other, textual information. This means there must be a keypad with around 12–20 keys and they should be of a size to facilitate pressing. Smaller phones will come. There are plans for ones which will fit in the ear, containing both the speaker and the microphone. The interface to such a device will have to be speech-based. Handheld Handheld devices such as the 3Com Palm have been around for some time, but recently devices of that size have become available which are truly personal computers. They have quite a small screen. As a computer, textual input is required, but lacking a keyboard, novel input such as a pen is required. They are essentially pocket-sized. Palmtop/wearable The next size up is the palmtop computer. The difference from the handheld is that this does have a keyboard. The keys are generally quite small, so that rapid, efficient input is difficult. If a strap or belt loop is attached then it becomes a wearable. Laptop Once a full-sized keyboard is attached, the computer becomes a laptop. It is portable but cannot be carried around on the person; it generally is carried in a bag or case. Efficient typing is possible. The screen is of a size comparable to a sheet of paper. There is room for peripheral components such as DVD or other disc drives. Desktop Now we have reached the size that cannot be said to be portable. That very lack of mobility may be one of its assets, to the extent that they are less easy for the ‘wrong’ people to move; they are harder to steal. Components can afford to be larger, so that a generously sized screen can be used and so on. Bigger I seems unlikely that there is any need for any computer much bigger than the desktop machine. Even the modern supercomputer is not much larger. A large machine has a property of permanence: it is going to be even harder to steal. The only other attraction

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may be a matter of perception of worth; I may feel more comfortable about spending a lot of money on a computer if it looks large and substantial. 5. Implications For the most part it seems that we might as well design devices to be as small as possible. We can identify the largest component, as dictated by the tasks we want the user to be able to perform. For instance, we may decide that (efficient) keyboard input is required, and therefore we are looking at something in the laptop size range. Beyond that, for the most part, we will go for the smallest size – because the product might as well be portable. In this situation the way that we use the technology will certainly change. One trend will be to the information appliance paradigm, described by [Norman, 1998 #796]. To design a new device and decide on its size, one should go through a process along the lines of that outlined in Figure {F1}. First the designer must decide what are the priority features are, as listed in the column headings. Then you scan down the rows until you locate the highest shaded row in any of the categories you have identified. The relevant device size is then given by the label on the right of that row. For instance, if permanence is required, then the top row (mainframe) is the only one with that property. If permanence is not important, though, then you effectively choose the smallest device that can accommodate the I/O devices that you require. Notice that palmtops and phone have the same profile – but that is not a surprise given the convergence of those two technologies in currently available devices. ‘Permanence’

Large screen

Small Screen

Peripherals

Fullsized keyboard

Occasional text entry

Immediate access Mainframe Laptop Palmtop Phone Watch Miniature

Figure {F1}. Outline of a design process for deciding the size of a new device.

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6. Acknowledgements Thanks to the members of the HCI Research Group at the University of York for their input to the ideas in this paper. 7.

References

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