System Analysis and Design Chapter 1

                 System Analysis and Design                 Chapter 1

1.1 What is a System ?

“A collection of interrelated components that work together to achieve some objectives”

Real world system

 •There are millions of systems in operation in the world     around us at every moment in time.
•Note : Not all systems are dependant on the involvement of computers
•Examples
•Family unit, school unit
•Digestive system
•Information systems•Radar systems

•A system has three stages...1.Something feeds into the system (the input)2.The system does something with the input (the process)3.The process gives a result (the output) 

 

1.1.2 Factors to be considered 

Factors to be considered when developing a system•Objective setting : What the system supposed to do.•System boundary : this defines the components that make up the system•System environment : anything outside the system boundary

What is subsystem? 

•“A system that is part of some larger system”•Each subsystem carries out part of the system function•Subsystems communicates by passing  messages between themselves•A good system will made up of highly independent subsystems with minimal flow between them•Advantages
•Help to handle system complexity
•Improve the understanding of the system

What is an Information System ? 

“Information system is an arrangement of people, data, processes, communications, and information technology that interact to support and improve day-to-day operations in a business, as well as support the problem-solving and decision-making needs of management and users ”

•Information systems are crucial to the success of modern business organizations

•New systems are constantly being developed to achieve

•Operational Excellence : efficiency, productivity
•New product services and business models : create opportunities to for products, services, and new ways to engage in business

•Customer and supplier intimacy : improved communication with customers and suppliers •Improved decision making : accurate and timely 
•Competitive advantage : effective and efficient information system improve profit than competitors.
•Survival : necessity of doing business 

 •The key to successful system development is through systems analysis and design••System analysis and design is used to analyze, design and implement improvements in the functioning of businesses that can be accomplished through the use of computerized information systems.

Software Development Process/ Systems Development Life Cycle (SDLC)

•Process used in the system development
•The process (as a whole) of developing system or software to meet certain requirements.
•SDLC is a process of gradual refinement/modification, meaning that it is done through several development phases.

4 fundamental phases 

 •4 fundamental phases which are common to all software processes

1.Software specification2.Software development3.Software validation
4.Software evolution
•Different software processes decomposes these activities in different ways

Waterfall Model 

 •The waterfall Model illustrates the software development process in a linear sequential flow.
•Any phase in the development process begins only if the previous phase is completed
•Does not define the process to go back to the previous phase to handle changes
•So suited for projects where the requirements can be clearly defined 

•The linear cycle is usually with structured teams and documentation systems••Documents flows also highly structured
••Documents produced at the end of the phase must be available for the input of next stage.

Waterfall Model 

Principal stages of the model map onto the fundamental development activities

•Requirement analysis and definition

•System and software design :

•Implementation and unit testing

•Integration and system testing

•Operations and maintenance 

•Advantages and disadvantages of waterfall model