It is normal for a team of people to work on the development of a new information system.

GCSE ICT 3rd EditionGCSE ICT 3rd

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The system life cycle18The system life cycle is a series of stages that are

worked through during the development of a new information system.

A lot of time and money can be wasted if a system is developed that doesn’t work properly or do exactly what is required of it.

A new system is much more likely to be successful if it is carefully planned and developed.


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The system life cycle18It is normal for a team of people to work on the development of a new information system.

This group is called the system development project team.

Most of the members of this team will be systems analysts.

A systems analyst is responsible for finding out about the existing system, designing a new system to replace it and supervising its development.

The other members of the team are programmers.

Programmers write computer programs that match the design specifications given to them by systems analysts.


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The system life cycle18Stages of the system life cycle


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The system life cycle18The feasibility study is an investigation carried out by systems analysts to find out:

what the main problems are with the existing system

if it is technically possible and cost-effective to solve these problems by developing a computer based solution.

At the end of this stage a feasibility report is produced.


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The system life cycle18A feasibility report should contain:

a description of the existing system outlining what is being done and how it is being done;

a set of problem statements describing exactly what the problems are with the existing system;

a set of system objectives which describe what the new system must be able to do;

a description of some alternative solutions;

a description of the technical, economic, legal and social factors that have been considered;

a recommended course of action.


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The system life cycle18During the analysis stage systems analysts investigate the existing system to identify exactly what the problems are with the existing system

Systems analysts use a variety of fact-finding methods to gather information such as:

questionnaires;

interviews;

observation;

examining documents.


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The system life cycle18


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The system life cycle18Once systems analysts have completed their investigation they produce a detailed description of how the existing system works.

Methods used to help describe the system include data flow diagrams and systems flowcharts.


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The system life cycle18Symbols used in Data Flow Diagrams

External entity – data source or data destination, for example people who generate data such as a customer order, or receive information such as an invoice.

Process – an operation performed on data. The two lines are optional; the top section of the box can be used to label the process, the middle to give a brief explanation, the bottom to say where the process takes place.

Data store – such as a file held on disk or a batch of documents

Data flow – the arrow represents movement between entities, processes or data stores. The arrow should be labelled to describe what data is involved.


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The system life cycle18Symbols used in systems flowcharts


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The system life cycle18During the design stage:

alternative possible solutions are identified;

alternative solutions are evaluated;

the best solution is identified;

a design specification is produced containing information about:

input;output;data storage;user interface;backup and recovery procedures;security procedures;testing the new system.


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The system life cycle18Typical format for a test plan

Test No

Test Data Purpose Expected Result Actual Result

1 Enter a mark of ‘50’ ; this is within the range

Test input mark function Mark accepted

2 Enter a mark of ‘0’ ; this is on the limit of the range


3 Enter a mark of ‘100’ ;this is on the limit of the range


4 Enter a mark of ‘101’ ;this is out of the range

Test input mark function Mark rejected


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The system life cycle18The implementation stage involves:

Setting up the system so that it matches the design specification.

Testing to make sure that all the parts of the system work correctly with normal, extreme and erroneous data.

Normal test data is used to check that a system can handle the sort of data that would be expected during day-to-day use

Extreme test data is used to check that a system can cope with data that lies on the boundaries of what is acceptable

Erroneous (or exceptional) test data is used to check that a system can identify data that is wrong and reject it.


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The system life cycle18 Installing the new system – this might include:

installing any new hardware and software;

transferring data from the existing system to the new one;

training users how to operate the new system.

producing user documentation and technical documentation for the new system.


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The system life cycle18User documentation should contain:

a description of what the system is designed to do;minimum hardware and software requirements of the system;instructions on how to load and run the system;detailed instructions on how to operate each part of the system;error messages, their meaning and how to deal with them.where to get more help, such as telephone support lines and on-line tutorials.


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The system life cycle18

Part of the user documentation for a new video rental shop system.


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The system life cycle18Technical documentation should contain:

the system design specification;

systems flowcharts;

data flow diagrams;

a description of the various parts of the system and what each one does;

screen layouts and user interface designs;

a test plan.


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The system life cycle18A post implementation review or evaluation should be carried out after a new system has been running for a few weeks or months to identify any modifications that may need to be made.

Modifications identified as a result of a post implementation review or evaluation are made during the maintenance stage of the system life cycle.

It is normal for a team of people to work on the development of a new information system.

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