Systems Life Cycle

A summary of what needs to be done.

Identify problems with existing data

Evaluate the new system

Maintain the new system

Implement the new system

Produce Documentation for the users

Test the new system

Build the new system

Design the new system

Analyse the new system’s requirements

Carry out a Feasibility Study

Fact FindingThis is concerned with finding out about the

current system

There are 4 main ways of doing this:

Interviews

Questionnaires

Observing how a job is done at the moment

Study documents – reports, printouts, etc.

This identifies any problems and allows the Analyst to see how the present system works.

Analysis -Feasibility Study

This study analyses the requirements of the new system and helps decide if it is worthwhile creating it.Decide on the objectives of the new system Identify the Hardware and Software needed.Carry out a Cost-Benefit study.Make a recommendation – should they go ahead with the new system, which option would be the best solution.

Objectives Of A System

Data is processed faster

Objectives

Lower Costs

Better stock control

Fewer staff needed to process orders

Less paperwork

Fewer mistakes with orders

Costs Associated

Costs of a system

Equipment costs

Operating costsPersonnel

costs

Installation costs

Costs of developing system

Design

Input – How the Data is CapturedDecide where the data will come fromDesign the data capture formsDecide how the data needs to be

structuredDecide how the data will be inputDesign the input screenDecide how the data will be validated

Process – What Happens To ItList the tasks that need to be done – based

on original problem and objectivesWrite the commands that enable them to

be done – e.g. exchanging data between different applications

Produce a plan to test if the processing works – typical data, extreme data and invalid data

Output – Let it OutDecide which data needs to be outputDecide how to present the informationDecide which output devices to useDesign output screen – should be sketched

first and shown to the user to check.

Top Down – Main Tasks

Looks at the whole system by identifying the main tasks and then breaks them down into smaller tasks.

Reading from left to right tells you the order in which they happen

Shows what has to happen, but not how

Create new patient record

Collect patient data

Enter patient data

Print patient data

Give patient data capture form

Patient completes data capture form

Load patient file

Create new record

Enter new record

Print Preview

Print record

Data Flow DiagramsShows how data moves around the system and what happens to it at each stage

They don’t show what hardware or software is needed for this to happen

Each tasks is created separately and can be linked together to show the whole system

Systems Flow ChartsShows exactly how the data moves through the system

Testing

There are 2 types of testingSystems testing Tests to see if the design works. Test data is used – normal data (should

work); Invalid data (should be rejected)

Acceptance Testing Does the system meet the needs of the

userOften involves a trial

User DocumentationWritten to help people use the system. This

can consist of 3 guides

Installation guide Installing the system and loading software Which peripherals required and how to install

User guide How to perform tasks

Tutorials Short training manual explaining how the system

works

Technical Documentation

Written for computer engineers and programmers who maintain the system after it has been installed.

Often full of technical language and systems diagrams

Gives advice on problems which may occur and upgrading of the system

ImplementationThere are 3 different ways of

implementing a system:

Direct – No change over. One begins as the other finishesAdvantages: Happens as quickly as

possibleDisadvantage: Disastrous effect if bugs not

found in testing

Phased – Introduced in different partsAdvantage: Time to fully testDisadvantage: Takes long time to

introduce full system

Parallel – Run both systems together while new one is testedAdvantage: system can be tested quicklyDisadvantage: Tasks need to be done

twice

Evaluation

Does the system still meet its objectivesRepeating research carried out at the beginning of the system’s life cycle – observing, interviewing and studyingIf it does not meet its objectives then the analyst is back at the start working on a new system – reasons: increased work load; system unable to cope with demands

Quiz

1. What comes between analysing and implementing a new computer system?

2. What are the 3 ways of gathering information about an old system?

3. What does a cost-benefit study do?

4. List three things that should be done when designing a system’s input.

5. List three things that should be done when designing a system’s processes.

6. List three things that should be done when designing a system’s output.

7. What is the difference between systems testing and acceptance testing?

8. How is phased implementation different to parallel testing

9. List three different types of user guide.

10. Why might a system not meet its objectives?