Systems Development Life Cycle
The stages of developing a new system are sometimes referred to as the “systems development lifecycle”.
The term “lifecycle” implies, producing a new information system is not a one-off exercise involving a few months of activity.
Once developed it will need maintenance, and eventually will be seen as inadequate to meet the users’ needs so a new system will then need to be developed, and so on.
The lifecycle goes through a number of stages, but a particular one may need to be repeated.
Stages of SDLC
- Preliminary Study
- Feasability Study
- Construction the solution
- Installation and Conversion
- Review and Maintenance
· A brief look at whether or not the new system is needed
· Managers initiate the preliminary study of they feel the present system doesn’t function well or that a new system might lead to improvement in productivity or quality
· Looks at the existing system and possible alternatives, including a new system or upgrading the old one.It considers the 5 following factor:
technical. will the new system work?
economic.will a new system save money?
legal. does a new system comply with the law?
operational. will a new system really solve the problem?
schedule. can a new system be built in time to produce benefits?
· A feasibility study produces a formal report for the management of a company, which then decide whether to give the approval to continue.If they continue, management then decide on a budget for the system
Analysis of the problem and proposed solution
An investigation (by interview, questionnaire, observation and detailed study of documents) into the current system to see how it works and what is required from the new system
Final deliverables need to be agreed at this stage and noted down to prevent confusion and arguments later on
· Design stage determines how the requirements specification is implemented
· It involves breaking the problem down into smaller sub-problems, such as:
- The fields and tables of the database
- Input formats
- Output formats – both for screens and printed output
- Macro designs
- The test plan
· A system specification is made in sufficient detail for the programmers to create the system
· Clear timescales are needed to prevent the project from over-running: A project timetable and milestones – deadlines for each part of the work – will be included in the design
Constructing the Solution
· This is the stage when the system is produced by the development of programs or customisation of software package
· Programs are coded, tested and documented
· Apart from the smallest projects, a team of programmers will be involved
· Vital that work is monitored very carefully, and that timescales are kept to
· Files need to be converted into a form suitable for the new system
· Hardware must also be installed and thoroughly tested
· Installation may require extensive cabling and alteration of buildings
Test data should test that all branches of the program perform to specification. Data should be used to test extreme cases.Testing should also include invalid data to ensure it is rejected
· It’s crucial that the results produced by the program are compared with expected results. Any discrepancies should be investigated and corrected if necessary. Types of testing include:
Installation and conversion
Hardware must be purchased, staff trained, user documentation written and data files converted for the new system.
Review and maintenance
· Once a system is in full operation it’s monitored to check it has met the objectives set out in the original specification.
· Obviously, will need to be made to the systems – changes known as systems maintenance.
· It’s necessary to evaluate the success of the project and review its effectiveness – such evaluation will involve returning to the original objectives and performance criteria to assess how well they have been met.
· Evaluation – involves discussions with management and users of the system some time after it has been installed to gather their opinions as to the new system’s effectiveness.
· Surveys can be used to find out if the information flows are correct and whether or not the information that is delivered is of high quality.