Purpose of analysis 
The main purpose- to investigate a problem(s) with an information system.
The solution to the problem can be either improvements within the existing system or creation of a new information system.
The systems analyst(s) who will be investigating the current system may have little or no knowledge of how the existing organisation works.
The systems analyst will have to investigate the present system to establish user requirements.
In order to do this the analyst needs to understand the purpose of the business or organisation and its existing system in terms of inputs, processing and outputs.

This will also include any constraints to be placed on the new system such as timescale, cost, existing hardware and software and staff capability.

Design
The purpose of the design stage is to produce a Systems Specification.
This document will include detail on a number of design components including:
Data capture methods and forms for the system
Data inputs and outputs for the system including screen designs, report specifications, query designs, storyboards, macros
Data processing within the system
Data structures such as: Database structure, Data Models, DFDs, normalisation.

Development

The purpose is to develop the software package required for the information system.

In order to do this appropriate programming code needs to be produced or the features of the software package need to be developed.

Aspects such as data structures, data checking procedures and the user interface also need to be developed.

As part of the development stage there also needs to be evidence of effective use of the hardware specification


uPrototyping Cont.
uThe result of these refinements may result into a fully working system which is known as Evolutionary Prototyping or produce a set of user requirement which is known as Throw-away prototyping.
uThis system is then fully developed using an alternative approach such as Waterfall method.
uA prototype which is usually a practical implementation of the system is produced to help discover requirements