SYSTEM DEVELOPMENT LIFE CYCLE

A System development life cycle consists of the following five phases.

1. preliminary investigation
2. system analysis
3. system design
4. system acquisition
5. system implementation


PRELIMINARY INVESTIGATION

During this the analyst studies the problem briefly and suggests solutions to the management. it is one of the steps towards SDLC it is also called feasibility study. Feasibility Study — asks whether the managements' concept of their desired new system is actually an achievable, realistic goal, in-terms of money, time and end result difference to the original system. Often, it may be decided to simply update an existing system, rather than to completely replace one; The purpose of this study is to evaluate and define the problem area at hand relatively quickly, to see if it is worthy for study, and to suggest some possible courses for action.
In this phase analyst studies about the requirements of the system and the cost and benefit analysis.


SYSTEM ANALYSIS

It is an important stage of SDLC. In this phase the management decides that further development is wanted and the analyst studies the application area in depth. Analysis — free from any cost or unrealistic constraints, this stage lets minds run wild as 'wonder systems' can be thought-up, though all must incorporate everything asked for by the management in the Terms Of Reference section.
System analysis is a phase in which a problem is studied in depth and the needs of system users is assessed. The main activities conducted during system analysis are
· data collection
· data flow
· data analysis
· documentation

Data collection is to gather about the type of work being performed in the application under study and is ascertain what resources users need to better perform their jobs.
Data analysis the information gathered about the application, it must be analyzed that conclusions about the requirements about the new system can be drawn.

SYSTEM DESIGNS

System designs include the following things.

· DFD(data flow diagram)
· Data dictionary
· Normalization

Analyst designs a new model of the system and prepares a detailed list of benefits and costs. System design focuses on how the system will look like it consists of developing a model of new system and performing a detailed analysis of the system and costs.
Developing a Model of the New System
Once the analysis understands the nature of the design problem, it is usually helpful to draw the diagrams of the new system.
Analyzing Benefits and Costs
Most organization are actually sensitive to costs including computer system costs. Costs of a new computer system include both the initial investment in hardware and software and ongoing expenses such as personal and maintenance.
Design — designers will produce one or more 'models' of what they see a system eventually looking like, with ideas from the analysis section either used or discarded. A document will be produced with a description of the system, but nothing is specific — they might say 'touchscreen' or 'GUI operating system', but not mention any specific brands
o Designing the technical architecture – choosing amongst the architectural designs of telecommunications, hardware and software that will best suit the organization’s system and future needs
o Designing the systems model – graphically creating a model from graphical user interface (GUI), GUI screen design, and databases, to placement of objects on screen
o Write the test conditions - Work with the end users to develop the test scripts according to the system requirements



SYSTEM ACQUISITION

Upon the managments aproval of the design the analyst decides which vendors to use inorder to meet hardware software and servicing needs.In this phase the the software, hardware have been specified.
RFPs and RFQs
Many organizations formulate their byingor leasing needs by preparing a document called request for proposal.
Some organizations know exactly mhich hardware, software and server sources it sends a vendor a document called a request for proposal.