7.1 SDLC(System Development Life Cycle):
System development life cycle is a sequence of events carried out by analyst, designers and users to develop and important an information system.
Activities are carried out in different stages.
The phases are as follows:
- Preliminary Investigation (Feasibility Study)
- Determination Of System Requirement
- Design Of The System
- Design Of The System
- Development Of Software
- System Testing
- System Implementation
- System Maintenance
1. Preliminary Investigation (Feasibility Study):
An important outcome of this preliminary investigation is determining whether the System requested is feasible or not.
The major purpose of this study are listed below:
Identify the responsible users and develop an initial scope of the system.
Identify current deficiencies in the user’s environment determine objectives for the new system
Determine whether it is feasible to automate the system and if so suggest some acceptable options:
The three major areas to consider while determining the feasibility of a project are:
- Technical Feasibility
- Economical Feasibility
- Operational Feasibility
The Analyst finds out whether current technical resources, which are available in the organization, is capable of Handling user requirements.
Economical or financial feasibility is second part of resource determination. Basic resources to consider are:
- Management time
- Time spent by system analysis team
- Cost of doing the full system study
- Estimated cost of hardware
- Estimated cost of software
Operational feasibility is dependent upon determining human resources for the project. It refers to projecting whether the system will operate and be used once it is installed.
The document to be produced at the end of this activity is called “FEASIBILITY STUDY REPORT”
2. Determination Of Requirements (Analysis)
Determination of system requirement involves studying the current business system in Great detail to find out how it works and where improvements have to be made.
This activity is carried out in two phases
- Detailed investigation
- Analysis or determination of system requirement
The heart of the system analysis is aimed at having a detailed understanding of all-important facts of the project under consideration. Analyst working closely with employees and managers must be able to answer the following key question:
What is being done by the current system?
How is being done?
How frequently does it occur?
How big is the volume of transactions or decisions?
How well is the task being performed?
Does a problem exist?
If problem exists, how serious is it?
If a problem exists, what is the underlying cause?
To answer the above question system analyst talks to a variety of people to gather details about the project. Questionnaires are used to collect this information from large groups of people who Cannot be interviewed individually. Detailed investigations also require the study of Manual and reports, actual observation of work activities and collection of existing Forms and document to fully understand the project.
Analysis or determination of system requirement
It is during this phase that the analyst and the user come to an agreement on
what Functions the proposed system has to perform.
A detailed document has to prepare by system analyst containing the following:
- Inputs that must be received by the system
- The outputs to be produced by the system
- The data to be retained
- The procedures to get the output from the given inputs
- Audit and control requirements
- System acceptance criteria
This detailed document is called functional specification or proposed procedures
3. Design Of The System
The design process should take care of the following:
- Identification of reports and outputs the new system should produce.
- Scrutinize the data present on each report/output
- Sketch the form or display as expected to appear at the end of completion of the system. This may be done on paper or on a computer display using one of the automated system design tools description of data to be input calculated or stored individual data items and calculation procedure written in detail.
- The procedures written should tell how to process the data and produce the output
The document produced at the end of this activity is called design specification
4. Development Of Software
In this stage the actual coding / writing of the program is done. Analyst – programmers do analyst and designs well as code programs programmers are responsible for documenting the program including comments that explain both
how and why certain procedure was coded in specific way. Programs are individually tested using some test data. Documentation is also essential to test the programs and carry out maintenance once the application has been installed.
This activity of system development life cycle produces tested programs.
5. System Testing
Once the programs are tested individually the system as a whole needs to tested. During testing the system is used experimentally to ensure that the software does not Fail that it will run according to its specifications and in the way user accept it too. special test data is prepared as input for processing and the result are examined to Locate unexpected result.
6. System Implementation
in this stage the system analyst uses new software, which has been tested into use. user personnel are trained and any files of data needed by the new system are constructed. Thus new software is installed and then used.
7. System Maintenance
Once installed the software is often used for many years. However both the organization and user change. The environment may also change over a period of time; therefore The software has to be maintained.
7.2 DFD(Data Flow Diagram):
They are the versatile diagramming tools used for structured system analysis. They are specifically used for process modeling which involves graphically representing the function or process, which captures, manipulate, store, and distribute data between a system and its environment and between components within a system.
7.3 CONTEXT DIAGRAM:
This is the start point of data flow diagramming process. It is denoted as the highest-level diagram. It gives an overview of an organizational system that shows the system boundaries, external entities that interact with the system and the major information flows between the entities and the system