SAD-The System Development Life Cycle

System development life cycle is also referred as system study. The system analyst gives a system development project meaning and direction. A candidate system is approached after the analyst has a thorough understanding of user needs and problems.

System development life cycle has 6 phases. They are
1.Recognition of need
2.Feasibility study
3.Analysis
4.Design
5.Implementation
6.Post-implementation and maintenance

RECOGNITION OF NEED

One must know what the problem is before it can be solved. The basis for a candidate system is recognition of a need for improving an information system or a procedure. For eg: a supervisor may want to investigate the system flow in purchasing or a bank president has been getting complains about the long lines in the drive-in. This need leads to a preliminary survey or an initial investigation to determine whether alternative systems can solve the problems. It entails looking into the duplication of efforts, bottleneck, inefficient existing in procedures or whether parts of the existing system would be candidates for computerization.

FEASIBILITY STUDY.

Depending on the results of the initial investigations the survey is expanded to a more feasibility study. We can define feasibility study as a test to a proposed system according to its workability, impact on the organization, ability to meet user needs and effective use of reasources. The objective of a feasibility study is not to solve the problem but to acquire a sense of its scope. During this study, the problem definition is crystallized and aspects of the problem to be included in the system are determined.

The result of the feasibility study is a formal proposal. This is like a report. This report summarizes what is known and what is going to be done. It consists of the following.

1.Statement of the problem:- a carefully worded statement of the problem that led to analysis.
2.Summary of findings and recommendations:- a lists of the major findings and recommendations of the study
3.Details of findings:-an outline of the methods and procedures undertaken by the existing system
4.Recommendations and conclusions:-specific recommendations regarding the candidate system, including personnel assignments,costs,project schedules and target dates.

Then the management reviews this report. After the proposal is reviewed, it becomes a formal agreement that paves the way for actual design and implementation.

ANALYSIS

Analysis is a detailed study of the various operations performed by a system and their relationships within and outside of the system. A key question is: what must be done to solve the problem?. One aspect of analysis is defining the boundaries of the system and determining whether or not a candidate system should consider other related systems. During analysis data are collected on the available files, decision points and transactions handled by the present system.

Data flow diagrams, interviews, on site observations and questionnaires are some tools that are used in analysis.

DESIGN

The most creative and challenging phase of system life cycle is system design. The term design describes a final system and the process by which it is developed. It refers to the technical specifications that will be applied in implementing the candidate system. It also includes the construction of programs and program testing. The key question here is how should the problem be solved?

There are four steps in design phase. They are

Output design: This step is to determine how the output is to be produced and in what format.
Input design: In this step the samples of input and its format is finalized.
File design: In this step the master file , transaction files have to be designed.
Processing design: This is also called Operational Phase. In this step the program construction and testing is performed.

Finally details related to justification of the system and an estimate of the impact of the Candidate system on the user and the organization are documented and evaluated by management as a step to word implementation. The final report prior to the implementation phase includes procedural flow charts , report layout and a workable plan for implementing the candidate system.

IMPLEMENTATION:

The implementation phase is less creative than system design. It is primarily concerned with the user training , site preparation and file conversion . During the final testing user acceptance is tested followed by user training. Depending on the nature of the system extensive user training may be required .Conversion usually take place at about the same time the user is being trained or later.

System testing checks the readiness and accuracy of the system to access, update and retrieve data from new files. Once the programs become available test data are read into the computer and processed against the files provided for testing. If successful the programs is then run with live data . Otherwise a diagnostic procedure is used to locate and correct errors in the program.

POST IMPLEMENTATION AND MAINTENANCE:

Like any system there is an aging process that requires periodic maintenance of h/w and s/w . If the new information is inconsistent with the design specification, the changes have to be made. Hardware also requires periodic maintenance to keep into with the design specification. The importance of maintenance is to continue to bring new systems to standards
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