A UI designer wants to design an application for people with difficulty using keyboard. comment on selecting proper device based controls.

Selecting the proper device based controls: A number of studies have been performed comparing the various controls for assorted office tasks. significant findings include the following:

Keyboard versus mouse.

Why do many skilled typist prefer a keyboard to a mouse? speed is obviously one reason. An experienced typist, through kinesthetic memory, has memorized the location of keyboard keys, The keying process becomes exceptionally fast and well learned. The mouse is slower and it has a tendency to move ob-cut the desk. Its location cannot be memorized. The keyboard keys always remain in the same spot.

Consider the following : when using the mouse, the time to move ones hand from the keyboard grasp the mouse and point at a screen object ranges from 1.5 to 2 seconds. A very skilled typist can type 13 to 15 characters in the amount of time, an average typist can be typed 4 to 6 characters: No wonder the keyboard is often preferred

Control Research:

Which devices work better for which tasks and under what conditions has been addressed by a number of investigators, A survey of the research literature comparing and evaluating different devices yields the following summarization concerning tasks involving pointing and dragging:

• The fastest tools for pointing at station targets on screens are the devices that permit direct pointing, the touch screen and light pen.

• In terms of positioning speed and accuracy for stationery targets, the indirect point devices the mouse, trackball and graphic tablet, do not differ greatly from one another. The joystick is the slowest, although it is as accurate as the others.

• A separate confirmation action that must follow pointer positioning increases pointing accuracy but reduces speed. the mouse offers a very effective design configuration.

• For tracking small, slowly moving targets, the mouse, track ball and graphic tablet are proffered to the touch screen and light pen because the latter may obscure the user view of the target.

• Another common manipulation task is dragging an object across the screen.

• The graphic tablet yielded best performance during pointing.

• The mouse yielded best performance during dragging.

• The track all was a poor performance for both pointing and dragging and it had a very high error rate in dragging.

Guidelines for selecting the proper device based controls:

• Provide keyboards for tasks involving:

• Heavy text entry and manipulation.

• Movement through structured arrays consisting of a few discrete objects.

• Provide an alternative pointing device for graphical on drawing tasks.

• mouse-pointing, selecting, drawing and dragging.

• Joystick-selecting and tracking.

• Graphic tablet-pointing , selecting, drawing and dragging.

• Provide touch screens under the following conditions:

• The opportunity for training is minimal.

• Targets are large, discrete and spread-out.

• Frequency of use if low.

• Desk space is at a premium.

• Little or no text input requirements exist.

• consider user characteristics and preferences

• Provide keyboards for touch typists, selection of the proper device for an application then depends on a host of factors.

Task characteristics: Is the device suited be the task? standard type writer keyboards are always necessary for the tasks requiring text entry and manipulation. keyboards are usually faster when moving through structures arrays consisting of a dew discrete objects.

User characteristics and preferences: will the user be able to easily and comfortably operate the control? are the fine motor movements required by some devices capable of being performed? is the user familiar with the standard keyboard? what are the users preferences? while preferences do not always correspond to performance. it is important that the user be comfortable with the selected device.

Environmental characteristics: will the device fit easily into the work environment? If desk space is necessary, does it exists and is it large enough?

Hardware characteristics : Is the device itself of a quality that permits easy performance of all the necessary tasks? joysticks, for example are quite variable in their movement capabilities.

Flexibility: Often task and user needs will vary within an application. providing move than one kind of device will give the user choices in how to most efficiently accomplish whatever tasks must be performed, A keyboard paired with another kind of pointing device is almost always necessary.

Minimizing eye and hand movements: When multiple devices are used eye and hand movements between them must be minimized. Structure the task, if possible, to permit the user to stay in one working area. If shifts must be made, they should be as infrequent as possible. It is estimated that, for a good typist, it costs 3 to 8 keys tokes for each jump between the keyboard and a mouse, The general rule is that more than 80 percent of the tasks should be doable using only one device.