System Design

We have discussed before about the first stage of the system life cycle, which is the system analysis. And based on the user requirements and the detailed analysis of a new system, the new system must be designed. This is the phase of system designing. It is a most crucial phase in the development of a system. Normally, the design proceeds in two stages :

preliminary or general design
Structure or detailed design
Preliminary or general design: In the preliminary or general design, the features of the new system are specified. The costs of implementing these features and the benefits to be derived are estimated. If the project is still considered to be feasible, we move to the detailed design stage.

Structure or Detailed design: In the detailed design stage, computer oriented work begins in earnest. At this stage, the design of the system becomes more structured. Structure design is a blue print of a computer system solution to a given problem having the same components and inter-relationship among the same components as the original problem. Input, output and processing specifications are drawn up in detail. In the design stage, the programming language and the platform in which the new system will run are also decided.

There are several tools and techniques used for designing. These tools and techniques are:

1-Flowchart
2-Data flow diagram (DFDs)
3-Data dictionary
4-Structured English
5-Decision table
6-Decision tree

Benefits:
1-Improved system performance; individually tailored configuration advice demonstrates where improvement is necessary, and how to improve the system to regain lost performance.

2-Customers gain a detailed understanding of how their users use their system. This Usage Profile can be leveraged to develop future architecture changes.

3-Potential to learn of future concerns, allowing customers to take proactive measures to avoid problems.

4-A baseline performance level is established against which benefits can be compared and changes to the system predicted or foreseen.

System Analysis

System analysis is the process of examining an existing system in detail, in simple terms analysis is to see what data comes in to the company, how it is processed and and what outputs they produce.The purpose of analysing the system is to see how data flows around the system. In particular the process of system analysis requires:

1-Collecting information on how the existing system works.
2-Establishing its inputs, outputs and processing.
3-Recording information, for example in the form of data flow diagrams.
4-Identifying problems.

As we have mentioned the first stage of system analysis is collecting information,and there are four methods of doing this:

1-Examination of documents
Examining all the documents within a system for example, bills, invoices, letters, order forms, payslips etc.

2-Questionnaires
The most common way of gathering information. It is a printed sheet given to the employees, which contains questions for them to answer about the system. For example, what details of the worker and their pay would you like to see on your worker's payslips?

3-Interviews
Preparing an interview with an employee on certain date, to discuss them about the system. But most probably employees will give false information.

4-Observation
Observing and having a look on the how the employees work, but most employees won't feel comfortable with this, and others might give wrong impressions while being observed, and so the analyst will get wrong information.