Systems Life Cycle PowerPoint - Intro to Systems

							The System Life Cycle

The systems lifecycle is the set of stages that are
followed when developing an information system
Summary Slide
 Systems Life Cycle
 What prompts a new system?
 Feasibility study
 Analysis
 System design
 Implementation
 System maintenance
 Systems Life Cycle
Systems Life Cycle

                     Feasibility
                       Study


   Maintenance                     Analysis




   Implementation                  Design



                    Programming
What prompts a new system?
 The current system may no longer be suitable for its
  purpose
 Technological developments may have made the
  current system redundant or outdated
 The current system may be too inflexible or
  expensive to maintain
Feasibility study
  – does the technology exist to implement the
    proposed system, or is it a practical proposition?


  – is proposed system cost-effective – if benefits do
    not outweigh costs, it’s not worth going ahead.

  – how long will the system take to develop, or can
    it be done in a desired time-frame?
Feasibility Study
The results of the investigation are provided
in a feasibility report:
•What needs to be done – a set of objectives
•A description of some alternative solutions
•A recommended course of action
Analysis
 The analysis is the first stage you must tackle
 when developing an information system.

 Analysis is the process of deciding what (if
 anything) the information system should do.
Method           Description

                 People who operate the current system can be interviewed to find out
                 what they think of it. Interviews can be in more depth than a
Interviews       questionnaire could be. If an interviewee makes a useful point about the
                 system then the person doing the interview can follow the point up to get
                 further information. This is not possible with a questionnaire.

               Questionnaires are useful when information about a system has to be
               gathered from a lot of people. Information can be obtained far more
Questionnaires quickly by using questionnaires than carrying out interviews. Because
               people can remain anonymous they may be more likely to tell the truth
               than they would in an interview.


                 Observation of how the current system works and what each person does
                 to use it can give an unbiased view of how the system works. Because the
Observation      person designing the information system is doing the observation himself
                 it is possible to get first hand information about how the system works.


              Manuals describing how the current system operates can be
              collected. Any forms used to collect information for the current
Documentation
              system or reports produced by the current system can be looked
System design

Design is the process of deciding how you will set up your
information system using the software packages you choose.

To produce a good design you need to show how you have
arrived at the design you are going to use, and not simply state
one design. i.e. you need to justify the choices you have made
and perhaps consider alternatives at each step in the design.
System design
The design stage will need to consider:
Input – what data will need to be input
Output – what output is required from the system
Data storage – what data files are needed; what field will be
used
Test plan – a plan for testing the system should be carried
out. This needs to consider the details of the purpose of each
test and the test data that will be used.
Implementation
 Implementation is using appropriate
  software packages to create the system
  you have designed
 During the implementation you need to
  collect evidence to show how the
  information system was created. If you
  decide to make any changes from your
  design then you will need to explain why
  the changes have been made, e.g.. Lists of data
  entered into the database; Example reports / queries
System maintenance
 Maintenance may need to take place when:
 – the system runs satisfactorily but there is still room
   for improvement.
 – All systems will need to adapt to changing needs
   within a company.
 – Problems frequently surface after a system has been
   in use for a short time, however thoroughly it was
   tested. Any errors must be corrected.
Systems Life Cycle

                     Feasibility
                       Study


   Maintenance                     Analysis




   Implementation                  Design



                    Programming
Summary Slide
 Systems Life Cycle
 What prompts a new system?
 Feasibility study
 Analysis
 System design
 Implementation
 System maintenance
 Systems Life Cycle