The discipline of usability or man/machine interface design is the study of communication between machines and humans. A machine can be anything from a wristwatch to a big factory. The communication can be the human pushing of a button or the machine flashing a lamp.

You have probably often been frustrated when trying to use some apparatus, whether it's a simple thing like a vending machine or a complicated thing like a new computer program: Which button should I press now? Why does it beep now? Why does it do something else than I want it to? The study of usability is very useful for knowing how to design things so that they are easy to use.

Some examples of usability problems:

  • How to design a TV so that the user can easily find the desired channel.
  • How to design a car so that the driver can use all the instruments without taking their eyes away from the traffic.
  • How to design a toilet so that users can choose between small flush and big flush even if they cannot read instructions in the local language.
  • How to design a piece of software so that novice users can find out how to use it without reading a big manual, and so that experienced users don't get delayed by having to click their way through a lot of menus.
  • How to design an information system at a train station so that passengers can easily find the right train.
  • How to design the control room of a big factory plant so that the operator can overview all the processes and also get detailed information about a particular process.
  • How to design a medical apparatus so that the doctor doesn't harm the patient by accidentally pushing a wrong button.
  • How to design an apparatus so that children, old people, and people with various handicaps can use it.
  • How to design an alarm system so that surveillance staff don't get too annoyed by false alarms and don't get lazy or fall asleep when there are no alarms.
  • How to design a computer mouse so that users don't get strain injury when using it all day.

Every serious company developing machines, user hardware, software, household appliances, or any other technical product used by humans should include usability considerations in their design process. Unfortunately, even the biggest and most renowned companies sometimes sell products with quite a poor and confusing user interface.

The study of usability will teach you what kind of usability problems to be aware of in the design process, how to test the quality of a particular user interface, and how to improve it.