2. the computer


Exercises 2.2 and 2.3 involve you examining a range of input and output devices in order to understand how they influence interaction.

A typical computer system is comprised of a QWERTY keyboard, a mouse, and a colour screen. There is usually some form of loudspeaker as well. You should know how the keyboard, mouse and screen work - if not, read up on it.

What sort of input does the keyboard support? What sort of input does the mouse support? Are these adequate for all possible applications? If not, to which areas are they most suited? Do these areas map well onto the typical requirements for users of computer systems?

If you were designing a keyboard for a modern computer, and you wanted to produce a faster, easier to use layout, what information would you need to know and how would that influence the design?

answer available for tutors only

The keyboard supports a single type of event, a keypress, which includes data that signals the value of the key pressed. This data is represented as an ASCII key value or some other international standard representation, such as UNICODE. Some keys on a keyboard introduce new modes, or interpretations of keystrokes, so you can use the same key to send uppercase and lowercase letters, or introduce special commands or modifiers (such as Control-A). Many keyboards also include special function keys, which produce non-ASCII keyboard events that must be handled in special ways. A mouse provides two main pieces of information. One piece of information is the location, in screen coordinates, of the mouse pointer. The other piece of information is any event information from the pressing and releasing of buttons of the mouse. Certain mouse designs include additional inputs, such as a wheel that sends discrete directional scroll events.

The information needed to redesign keyboard layout would include the frequency of letters or commands to be issued by the keyboard as well as empirical data on motor actions of the hands and fingers in performing typing actions. Various modified keyboard layouts do exist, such as the DVORAK keyboard, but none has been successful in supplanting the QWERTY standard.

Other exercises in this chapter

ex.2.1 (open), ex.2.2 (tut), ex.2.3 (open), ex.2.4 (tut), ex.2.5 (tut), ex.2.6 (tut), ex.2.7 (ans), ex.2.8 (ans), ex.2.9 (open)

all exercises for this chapter