6.1.2 Choosing programmes and parameters

Another part of the interface shown in Figure 15 allows the user to select one from a variety of predetermined washing programmes, and to change some of the parameters. If I choose the ‘cotton’ programme, for example, the microcomputer's program assumes that I wish to wash this load of laundry at 60°C, use the main wash programme, and spin the washing at the highest speed. Sometimes this programme is fine, but at other times I may want to select the higher temperature of 90°C in order, say, to sterilise the laundry (e.g. nappies), or a lower temperature (e.g. to prevent dark colours fading).
I may also select the pre-wash if my laundry is especially dirty or the additional rinse if a member of the family has sensitive skin which may react to residues of washing powder.
Finally, the microcomputer's program ensures I don't do anything silly. For example, if I select the ‘hand wash’ programme, it will not allow me to change the temperature to one higher than the pre-programmed 30°C.

Exercise 14

What kind of interface would you expect on a very simple microwave oven (one without predetermined programmes)?

Discussion

Since power level (e.g. defrost, low, medium and high) and time are important when microwaving food, the user needs to be able to select these two parameters.
Typically, a microwave interface will have buttons or a dial for selecting the power level, and a numeric keypad or dial for setting the time in terms of minutes and seconds. The display might indicate the power level chosen, and will certainly show the time remaining.
The interface will also have two other important controls: a ‘Start’ button and an ‘Open door’ button.
You may have said something a bit different, depending on your familiarity with microwave ovens.