Demonstration of the cycles in a computer system

Developing and activating a new computer system is a long process. It is important to break the process down into smaller stages, each one requiring a different set of professional skills.

An important part of this process is the first stage – analysis. During this stage the systems analyst will investigate how the current system works and what needs to be improved. This involves finding out whether a new computer system is needed at all and exactly what it will be used for.

Analysis is all about looking at how a job is done at present and seeing if the job could be done better or more efficiently by upgrading or developing a new system.

With this goal in mind, the systems analyst might:

  • observe staff at work
  • interview staff about their work
  • send out questionnaires about working practices
  • inspect documents such as user guides, data capture forms and any printouts the current system creates

Feasibility study

Having investigated the present system, the systems analyst will produce a feasibility study. This will look at whether the new system is:

  • Technically feasible – is the new system technically possible to implement in the time available?
  • Economically viable – will the cost of the new system be offset by savings once it is implemented, ie will it save the organisation time, money or increase its performance?

The project will only continue to the next stage if the answer to both of these questions is yes. At this point the decision makers in the organisation, eg the board of directors, decide whether or not to go ahead.


The next step is to draw up a requirements specification that outlines exactly what the new system will do. For example, it will mention:

  • what hardware is needed
  • what software is needed
  • what inputs are needed
  • what processing must take place
  • what information needs to be output


A test plan will be included in the design phase to explain exactly how the new system will be tested and the expected outcomes for each test.

Testing is important because computer software is usually very complex. Any mistakes made by the designers or programmer can have a dramatic effect depending on what the software is used for.

Usually software is tested with three distinct types of data:

  • typical data – this is normal data the system should be working with
  • extreme data – this is data at the boundary between typical data and invalid data
  • invalid data (sometimes known as erroneous data) – this is data that should cause the system to tell the user that there is a problem with data entered into the system

Testing helps to ensure that the system always acts as expected.


Implementation is the next stage of developing a new system, after design. This is where the new system is created and installed.

Tasks that might take place include:

If the tests are not satisfactory then any problems will need to be corrected and the system tested again.

User documentation

User documentation will be written to help staff become familiar with the new system. It will include:

Methods of changeover

When the system is ready to go on-line there are different ways of moving from the old to the new system:

Parallel running

Running both the old and new system until you are certain the new system is working correctly. Parallel running is likely to be the most expensive as it involves doing the work twice for a period of time. However, it is the safest. If there are any bugs in the new system, you can always go back to the old system while the problems are corrected.


Once the system has been installed it will be monitored to check whether it is working correctly. Sometimes problems with a system will not be found until it is being used by a large number of people or an unusual situation occurs.

Evaluation is really re-analysing – starting the same systems analysis process all over again. Many of the same techniques can be used, such as interviewing staff or sending out questionnaires.


Once a system is running correctly it can still need maintenance. This may be because a bug is found or because the company needs a new feature.