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System Life Cycle

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This is a revision guide for the GCE AS-level Applied ICT. Topic: Systems Life Cycle
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  Edited By. P. Materu Jaffery Academy 2012 Page 1   SYSTEMS LIFE CYCLE (SLC) The SLC consists of the following stages: 1.   Definition 2.   Investigation and analysis 3.   Design 4.   Implementation 5.   Testing 6.   Installation 7.   Documentation 8.   Evaluation 9.   Maintenance Although all projects should start with the definition stage and end with the maintenance stage, the process is not always completely linear. After completion of one stage, it might be necessary to return to an earlier stage. 5. Definition The very first part of the SLC is to define the problem. The system analyst must determine why  a new system is required. After all, if there isn't a problem to start with, why would an organisation incur huge costs to develop a new one? In the definition stage the role of the analyst is to scope out the problem. The analyst has a number of methods available to do this:- Interviews with management to get their viewpoint Interviews with staff to understand the limitations of the current system Other methods that will be discussed later in this mini-web  Edited By. P. Materu Jaffery Academy 2012 Page 2   6. Feasibility Study - constraints Once the system analyst is convinced that there is a problem which could be solved with a new IT system they have to determine whether it is feasible to actually go ahead and develop the system. Some of the questions that will need to be answered are: Cost How much would the new system cost to develop? Budget Would there be enough money available in the budget to develop the system? Time How long would it take to make the system from start to finish? Skills Does the company have the skills in-house or would it need to go to a specialist software development firm? Hardware to develop Does the company have the necessary hardware to develop the system? Hardware to run Would new hardware be needed to run the system and if so how much would that cost? Software Does the company have the necessary software to develop the system? Training What would the training implications be once the system had been developed? Technical feasibility After finding out what is required is it technically possible to create the system 7. Feasibility Study - alternative solutions The system analysis will consider all of the answers from the feasibility study and come up with a number of alternative solutions to present to management. It is then the management's job to consider going ahead with the new project. Some possible solutions that might be suggested to management could be: a) Company does not change anything Benefit No disruption to the business. Cost No cost. Performance No change, system remains outdated. Process becomes increasingly less efficient.  Edited By. P. Materu Jaffery Academy 2012 Page 3   b) Company makes alterations to half the system Benefit Best parts of the system are retained whilst the least efficient aspects are redesigned to enhance performance. Cost Moderate, training moderate. Performance Performance improvement: 30% c) Complete overhaul Benefit Reduces company cost base (more profitable). Cost High, given that new equipment / software will be required. Training for staff needed. Performance 70% improvement over the old system. As you can see, deciding on the best alternative is often not simple - management have to take many factors into account. There are often complicated relationships between cost, performance and benefit. So at this point of the system life cycle, you know what the problem is and you are considering options. The various options are usually presented to management at this stage and it is up to them to make a decision as to how much investment they wish to put into the project. If the decision is made that it is worth developing a new system, the SLC will progress onto the next stage, Investigation and Analysis. If management decides to stick with the current system, the SLC will stop here. 8. Investigation and Analysis: investigating the system In order to reach this stage in the SLC, management would have listened to the alternative solutions presented by the system analyst and have decided to either commission a brand new IT system or have changes made to their current system. During the earlier 'definition' phase the analysis looked superficially at the current system and the potential benefits of a new system. During this 'investigation and analysis' phase they will carry out very detailed investigations in order to fully understand the current system and the proposed new system. The current system    Edited By. P. Materu Jaffery Academy 2012 Page 4  how staff / customers interact with the current system i.e. how tasks are carried out how other systems interact with the current system what is good about the current system what causes problems with the current system which parts of the system are critical to the business The proposed new system  what the new system is expected to be able to do how the new system is expected to do this what people want from the new system which working methods from the old system should be incorporated into the new system 9. Investigation and Analysis: investigation methods In order to find the answers to the points on made on the previous page the system analyst will do some or all of the following: Face-to-face Interviews The analyst will interview selected staff who use the current system in order to get a detailed overview of how things work. They will want to know what the main problems are and whether users have any suggestions on how to improve the way things work. Observation The analyst will observe users actually using the system. They will  probably follow a complete process from start to finish and note down every interaction that happens Questionnaires Questionnaires enable the analyst to obtain the views of a large number of staff/ users. Questionnaires are also easier to analyse than face-to-face interviews but the trade-off is that they don't give as much detail. Examination of  business documents Most organisations have business documents and written processes/  procedures relating to the current IT system. These documents detail how the system works and the processes which users should follow. The analyst will examine these documents in detail. Paper trail Following information from the point it enters the system and observing what outputs are created at each point in the system.
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