Systems In Use

Context of Use

A key aspect of usability is that it refers to the quality of the system in use. The usability of interactive computer systems must be considered in the context of use, because many usability problems arise only when a system is being used by target users to carry out real tasks in the real working environment. Thus, the environment, tasks and user`s expertise must be properly considered in order to design usable systems.

Interactive computer systems are used to support people in their work and everyday activities. Some systems are used only by experts, whereas others are used by everyone. In fact, there are many different types of interactive computer system being used by different types of people in different environments.

Types of Interactive Computer System

It is possible to classify most interactive computer systems into one of five categories:

1) Walk-up-and-use Systems: everyday machines that can be found in public spaces (eg cash machines and vending machines)

2) Office Applications: desktop software (eg word processors, presentation and graphics packages)

3) Information Appliances: everyday devices (eg televisions, radio alarm clocks, and mobile phones)

4) Information Systems: business information systems (eg decision support systems and management information systems), or hypermedia and multimedia systems (eg interactive CD-ROMs)

5) Real-time Systems: including financial systems (eg share-dealing terminals), control systems (eg air-traffic control), and large plant processing and monitoring systems (eg chemical processing plant system).

Self-assessment Question 2

Below are five interactive computer systems. Place them all into one of the five categories introduced above, then check if you are right by pressing the 'feedback' button.

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Choose system! Walk-up-and-use system Office application Information appliance Information system Real-time system
Web site

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Choose system! Walk-up-and-use system Office application Information appliance Information system Real-time system
Spreadsheet

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Choose system! Walk-up-and-use system Office application Information appliance Information system Real-time system
Power stations

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Choose system! Walk-up-and-use system Office application Information appliance Information system Real-time system
Pager

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Choose system! Walk-up-and-use system Office application Information appliance Information system Real-time system
Photo booth

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When designing these different types of interactive computer system, certain attributes of the systems are more important than others, due to the nature of the tasks and environments in which they will be used. So, greater emphasis must be placed on these aspects during design to ensure a satisfactory level of usability. For example, a cash machine must be extremely easy to learn how to use, as it is intended to be used by everyone, whereas a spreadsheet application need not be as accessible because people expect to undergo training to master its powerful functionality. On the other hand, cash machines can be rigid in the functionality that they offer because there is a limited amount of things that customers would want to do, whereas a spreadsheet application must be flexible, providing a large, extendible range of functionality to support the variety of user tasks.

The important attributes of two of these types of system will now be considered in more detail.

Walk-up-and-use Systems

Walk-up-and-use systems exist in public spaces and take the place of human assistants or operators. They therefore need to be designed so that everyone can use them with the minimum of effort.

Making systems of this type complex makes them unusable, given the environment in which they are employed. They have to be quick to use and reliable, because of the time constraints and pressure their users are usually under when interacting with them. People do not wish, and may not be able, to spend time mastering complex functionality, so they must have simple features that can be used instantly without being learnt.

One way to achieve this level of simplicity is to design systems with a fixed sequence of interactions. For example, having entered your card into a traditional cash machine, you are taken through a fixed sequence of screens, with occasional choices, until your card is returned to you. It is difficult to make a mistake, but, if you choose to withdraw money, you can’t go back and order a statement.

More recently, a new breed of machine has emerged that enables you to navigate more freely through the screens, enabling you to use features in any order. This extra freedom has made the cash machine more complex and, although people with experience of the old machines can soon learn how to use the new machines and benefit from the flexibility, novice users, who have never used a cash machine before, can find it more difficult to learn how to use the new machines than the old ones.

Information Appliances

Similarly, information appliances need to be designed so that anyone can use them. However, it is often desirable for such appliances to perform complex procedures, as they are required to automate some of our routine tasks. Appliances can afford to be more complicated than walk-up-and-use systems, because once installed in the home users have time to learn how to benefit from the advanced features. Nevertheless, it is imperative that the basic features can be used instantly, because users may be unwilling, and should not be expected, to consult manuals to learn features that they have employed before on similar appliances.

The video recorder is a prime example of an information appliance that must have instantly usable basic features, such as play and record, but be able to perform more complex functions. Most information appliances offer some degree of flexibility in their usage. For example, video recorders provide a few different ways to record programs. Typically, the user can press record and then stop, record for a fixed length of time from that point onwards, program the machine to record in advance by entering times, dates, lengths and channels, or even by entering cryptic Video Plus numbers.

The complexity of video recorders is often reduced by hiding the most advanced features away under panels on the machine or remote control. By hiding complexity and by using standard buttons for the basic features, video recorders are instantly understandable. Thus, it is desirable that information appliances have basic features that are instantly understandable, and hidden, easy-to-learn advanced features, because the user has only a manual from which to receive operational instruction.