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What are computer systems?

A computer is an electronic device that processes data by following a set of instructions. A computer system is a set of parts, including the computer itself, that work together to perform tasks. These tasks may be relatively simple, as in a calculator, or they may be very complex, as in air traffic control systems. The computer system that you are using now, probably includes a monitor, keyboard, mouse and the computer itself. Together, these help you to carry out a variety of tasks such as write letters, play games and surf the internet. We will be looking in detail here, not at computers themselves, but at the design of systems that are run by computers - they are 'computer-based'.

You may have computer-based systems in your home, for example, in your washing machine, in your car or in your watch. Can you think of any other items in the home that are computer-based?

Computer-based systems

Designing a computer-based system

If you are designing a computer-based system, you need to consider more than just the electronic components that make up the computer itself. You should think of all the stages that the system will go through, such as design, manufacture and use. For each stage, you will need to think of all the people that might come into contact with the system - these are the 'users'. You need to consider all the various tasks that they will carry out, what additional equipment that they might need and where they will perform their tasks. There must be a good match between the user, the task, the equipment and the environment, for the system to be effective and achieve its purposes.

You could use a step-by-step approach to make sure that you consider everything and give yourself the best chance of designing a successful system. We will use a digital camera as an example of a computer-based system throughout the following steps. Please note that the considerations given for the camera example are in no way complete, but are there to give you starting points.

Step 1 List all the aims of the system.
  What are the main functions of the system? What are the individual tasks that make up the main functions? You will need to break these down into as much detail as you can at this stage.

Task description is an essential first consideration when designing a system. The task description may be based on previous similar systems, where they exist. For example, there is a long history of designing cockpit instrumentation. In this case, the designers may have a relatively precise idea very early in the design about the information that is required and the controls that must be provided. On the other hand, the design of games consoles demands innovative thinking as the technology for handling images changes rapidly.

cameraThe main functions are to record digital photographs and video. The individual tasks include opening the lens cover, focusing on the subject, opening the shutter, recording and storing the image, closing the lens cover. We also want to include the use of flashlight, viewing and editing the recorded images, and giving a choice of image quality.

Step 2 Decide what tasks the system is to carry out, and what tasks the user is to carry out.
  This is called 'allocation of function'. It is where you start to think about the abilities of the users and the system in greater detail. What is the user capable of doing to meet the aims of the system? The tasks that the system carries out depend largely on the level of technology available. It also depends on how much you want to 'automate' the system, and how much you want to leave to the user to carry out and control. Automation is the process where a task, previously carried out by a user, is to be carried out by the equipment. There are a number of things that people are better at doing than computer-based systems, and the other way around. Obviously, people can think, make decisions and react to what is happening around them, computers only ever do what they are programmed to do, without change (unless they break down). This is one strength of a computer, it does not get tired, and if programmed well, it is consistent and does not make mistakes.

Are the tasks for the user difficult or complicated? Will they need much training or instruction? Once they learn how to do the task, will they do it often enough that they won't need reminding? Do the users need particular skills or attributes, such as strength?

You need to think about maintenance at this point too. Will there be automatic fault-finding in your system or will someone need to track down faults? Would automating certain tasks introduce new technology? Would this mean that the system might break down and need repair more often?

At this stage, you may start to meet 'constraints' - things that restrict what you want to do. It may be cost; you might want a task to be carried out by the system that would add to the cost of manufacture so much that it would make it too expensive for people to buy. You might have no choice but to give that task to the user. Another constraint may be time; you might have a deadline to meet for producing your system and to introduce an automatic task might mean additional research and development that means you would miss your deadline.

cameraDo you want the user to focus on the subject or do you want the camera to do it? Will the user be able to focus properly? What if their sight is not good? Might children use the camera? Will they know that they have to focus? Are there times when the user would want to focus manually? Should we give them the option of both automatic and manual focus? What about the flash? Should it operate automatically when lighting levels are low or should the user switch it on? How will the user know if the lighting is not good enough?

Step 3 Decide which are the best methods for control of the system and display of information, based on matching the user to the task, additional equipment and the environment.
  This is where you will need to consider your user's abilities and limitations in great detail. If the system has many complicated functions, it may need several control devices and several displays giving information about the status of the system. Each control and display will need to be matched to the user in terms of size, operation and understanding. See the topics on controls and displays for details. These features, together with the size of the remaining components, will determine the overall size of the system. Users may be able to carry the system around and use it (mobile phone), they may need or want to sit down to use it (supermarket checkout), or they may need to stand to see and reach all the features (power station control panel). You will need to think about positioning of controls and displays so that the user can see and reach everything they need to. If the system is portable, is it light enough for all users to carry it around when they need or want to, without strain?

Information flow should be considered. What does the user need to know and be able to communicate to the system, and what information does the user need from the system? The user can get information from the system in the form of light in a display, or sound, as in an alarm. Knowledge is created when the user receives the information, interprets its meaning, and turns it into an understanding of the system. Communication between the user and the system should be simple and quick. The rate at which information passes between the user and the system is an important characteristic of the system. The user may act infrequently, or there may a continuous interaction like a conversation. 

The overall effectiveness of the system will depend on how well the control devices match the task design. Some tasks are likely to be performed better with some types of controls than others:

  • Use a joystick, trackerball or mouse to move a cursor on a display
  • Use a keyboard or keypad to enter numbers or letters
  • Use a lightpen or touchscreen for immediate selection of items on a display
  • Use speech when the system can translate it into instruction.

There may be several reasons for choosing one control device over another. These may include the abilities of the users. The first three types of devices above depend on hand-eye co-ordination. Therefore, if the users are likely to have poor vision or poor hand control, then speech may become an important alternative. Similarly, if the users are likely to be busy with many hand controls, then foot controls or speech may be more effective. 

It is important to match features of the system to the way that users think, and to take account of their prior experience and expectations. If there is already a successful and well-known method of doing something, consider using it for your system. There is no problem with finding an alternative way of carrying out a task if it is an improvement, but it should not run against what the user might expect. In this case, users may make errors or become frustrated. An example is the three small boxes with symbols in them in the top right hand corner of windows on your computer screen. You know that they mean minimise, maximise and close window. It would be very frustrating to find that these functions have changed around and you closed a file when you meant to minimise it, for example.

You need to consider any other equipment that might have to be used with the system to achieve the system's aims, and make sure that the equipment is compatible with the system and the user.

If the system is to be operated by several people at once, or as part of a group of systems, then communication and interaction between all the users should be considered too. Will they need to talk to each other? Will they be close enough to hear? Will they need to use telephone or radios to talk to each other? This is where the physical environment will be important too. Will noise levels enable people to hear speech or alarms?

Will lighting be good enough to see displays? Lighting is a vital consideration as a display may be used in an areas where lighting varies hugely. For example, there is high illumination in an airport control tower during the day, with wide windows letting in lots of natural light, and low artificial lighting at night when the users may want to see out of the windows while at the same time using the display. This may mean designing a special workstation that has screening, or equipping the display with a light intensity adjustment. These are sometimes provided in cars to enable dashboard lights to be dimmed.

Does the system emit heat? Will it need special ventilation? Will it be used in particularly hot or cold environments. Will this affect the system, or the user? See the temperature topic for more information about suitable working temperatures.

cameraHow many controls will there be? Can they all fit on the camera and leave room to hold it without inadvertently operating one? Can controls be doubled up? Will this be confusing? Can all the information about the photographs and settings be displayed on one screen? Will the text be large enough? Will users understand symbols or do we need whole words? There needs to be a connection between the camera and a computer to download the photographs. Will this be a cable or will the camera plug directly into the computer, or a base unit? Will a cable have a standard connection? Will users understand what to do with it? Does the display light up for use in the dark? Does the camera need to be kept out of the sun, but not left in the cold?

Step 4 Design and build the system.
  Having selected types of displays and controls in general, you will need to specify the information to be provided on the displays and the precise means of exercising control. There are several ways of positioning displays and controls that will be helpful to the user. You will need to find out the information and knowledge required simultaneously, so that displays and controls can be grouped together. You also need to check the performance required in frequent, important or critical tasks to ensure that it is possible for the user to achieve the required levels and carry out the tasks. For example, will the user be quick enough to operate several controls in a certain sequence, in a certain time, if necessary? Ensure, too, that there is appropriate feedback to the user so that they have confirmation of their actions.

The detailed design of the screens for the system could conform to a 'style guide'. Style guides are detailed specifications of all the system's features, and are created and developed for  two main purposes:

  • To make the equipment recognisable as belonging to a particular brand.
  • To standardise the operation of a system and make it easy for the user to learn, or to bring their previous skills and learning into use.

Many examples of software now use the familiar style of windows, menus and icons, as this reduces learning time and programmers can concentrate on improving the functions of a system rather than the way it is used. International standards should be used where relevant for symbols, signs and colours.

The design of alarms and warnings needs to be considered very carefully, as they may have safety or operational implications, for example, lights or sounds may be used to warn drivers that a car door has been left open, or the car lights left switched on.

If at all possible, and time and money allow, build a mock-up of the entire system, or elements of it, and use it to try out the match between users and the system. It is quick and easy to test users' perceptions about the meanings of symbols - this can even be paper-based. Workstations can be mocked up full-size using cheap materials to make sure that displays and controls are within sight and reach of users. Feedback at this stage is invaluable and will improve the potential success of your system.

cameraThe camera will include a cable for connection to a computer and software to allow photographs to be downloaded from the camera to the computer. Standard computer connectors will be used to ensure compatibility with a high percentage of computers. A battery charger will be provided and a memory card to enable users to be able to operate the camera with no additional purchases. The camera will use menus and will give feedback to users by emitting a beep when menu selections are made.

Step 5 Test, install and evaluate the system
  Make sure that users can work the system to carry out the listed tasks and achieve the original aims. Test the system with a variety of users in real conditions. Make sure the system is safe. See the topic on product evaluation for more details.

The performance and effectiveness of a system should be checked. You should consider whether the system performs as specified. For example, if printing is a feature, does it provide a printout within a specified time when requested? What is the error rate? Is it acceptable? What are the causes of errors? Are they system or user errors? Are user errors due to mismatches between the user and the system?

cameraIs picture quality good enough? Is download of photographs successful? Is the casing strong enough to withstand outdoor use? How many times can the battery be recharged before it needs to be replaced?

Step 6  Provide users with training, instruction and support
  All systems need to have trained users before they can work effectively. Similarly they all need some maintenance and support even if it is only changing an ink cartridge in a printer or putting disks away carefully.

Ensure that users have all the information they need to operate the system. If the system is complicated, users should be given scenarios to enable practice without serious consequences for error. The amount of training and instruction needed will depend on the user and their knowledge and prior experience, and the complexity of the system. Users should be given training in a form and amount that they understand and are confident with.

Where performance is critical, it may be necessary to use simulators of actual operational conditions so that training can take place in a safe environment. For example, pilots can practice in flight simulators. Exercises may be conducted with larger systems to enable users to develop skills and knowledge in handling infrequent or hazardous operations. These might include medical response teams reacting to major emergencies. Military and public services exercise regularly to ensure that skills and knowledge are maintained in the use of large scale computer-based systems.

Provide maintenance manuals for complex systems. This should include removal (and possible dismantling) of the system. Troubleshooting guides are useful for home users of computer-based systems if solutions can be carried out by them without risk to safety.

Users should be given information about hazards - their effects and how to avoid them. This information should include disposal instructions, especially if there is hazardous material involved, for example, batteries.

cameraAn instruction booklet will be provided that includes use of software and computer connections. Use of the display will be shown in picture and text format. Battery and memory card maintenance will be explained. A simple troubleshooting guide will be included with contact information for further help.


Computer Systems FAQs

Q. Can you tell me how to apply ergonomics to computers? Answer

Galer, I (ed) (1987) Applied ergonomics handbook. (2nd ed) Oxford: Elsevier ISBN 0750617764

Content: Mike Tainsh, Tina Worthy
Images: IMSI's MasterClips Collection