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 Finding This 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 costs Personnel costs Installation costs Costs of developing system

Design Input – How the Data is Captured Decide where the data will come from Design the data capture forms Decide how the data needs to be structured Decide how the data will be input Design the input screen Decide how the data will be validated

Process – What Happens To It List the tasks that need to be done – based on original problem and objectives Write 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 Out Decide which data needs to be output Decide how to present the information Decide which output devices to use Design 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 Diagrams Shows 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 Charts Shows exactly how the data moves through the system

Testing There are 2 types of testing Systems 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 user Often involves a trial

User Documentation Written 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

Implementation There are 3 different ways of implementing a system: Direct – No change over. One begins as the other finishes Advantages: Happens as quickly as possible Disadvantage: Disastrous effect if bugs not found in testing

Phased – Introduced in different parts Advantage: Time to fully test Disadvantage: Takes long time to introduce full system Parallel – Run both systems together while new one is tested Advantage: system can be tested quickly Disadvantage: Tasks need to be done twice

Evaluation Does the system still meet its objectives Repeating research carried out at the beginning of the system’s life cycle – observing, interviewing and studying If 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?