CONTROLS FOR COMMUNICATION WITH COMPUTERS

The traditional controls in administrative computer systems are various different types of keyboards. There is often a numerical keyboard as well as the traditional typewriter keyboard. These types of keyboards have been tested over a long period of time and can be well specified. They are also thought to be well suited to most forms of administrative computer systems.

For more specialised applications—for example, computer systems for the con­trol and monitoring of process industries—the situation is often very different. The requirement for control devices is unique to each type of process industry, depending on the process to be controlled and the type of computer system installed. It is thus impossible to give any specific guidelines for the control devices on computerised control systems. However, some overall guidelines may be given. The advantages and disadvantages of different control devices for computerised systems are exam­ined here. Traditional control devices are rarely applied to computerised systems.

TABLE 5.4

relative advantages of Different Forms of Control Devices for Computerized process systems for Four Common Tasks

Task

1

2

3

4

numeric

alphabetic

position

Graphic

Control

data

data

Cursor

information

Fixed-function keyboard

u

vg

nk

nr

Variable-function keyboard

vg

nk

nk

nr

Lever

nr

nr

su

nk

Wheel

nr

nr

su

nk

Light pen

nk

nk

u

nr

Electronic data board

nk

nk

nr

u

Touch screen

u

u

u

su

Mouse

nr

nr

u

su

Joystick (trackball)

nk

nk

su

nk

Notes: su, may sometimes be usable; u, usable; vg, very good; nr, not recommended; nk, the advantages and disadvantages of the application are not known.

Thus this makes it difficult to give detailed guidelines for all controls in this context. Finally, some more detailed design recommendations for the different types of key­boards will be presented.