System Analysis and Design

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CHAPTER 1

INTRODUCTION

1. Concepts
System Analysis and Design in this unit (SAD) is the application of the system approach to the study and solution of problem using computer-based systems

Systems approach is a way of thinking about the analysis and design of a computer –based application. It provides a framework of visualizing the organizational and environmental factors that operate on a system.

Organizations are complex systems that consist of interrelated and interlocking sub-systems.

Systems analysis and design focuses on;
- Systems
- Processes
- Technology

What is a system?
The term system is derived from a Greek word Systema meaning an organized relationship among functioning units or components. OR;
A system is an orderly grouping of interdependent components linked together according to a plan to achieve a specific objective.

A Component may refer to: Physical parts e.g.; engines, wings of air craft, wheels of a car etc; Managerial steps (planning, organizing, directing and controlling);A sub-system in a multi-level structure.

A system exists because it is designed to achieve one or more objectives. Examples of systems: Transpiration system, Telephone system, Computer system e.t.c

2. Characteristics of a system
1. Organization (order)
2. Interaction
3. Interdependence
4. Integration
5. A central objective

Organization: This implies structure and order. It is the organization of components that help to achieve the objectives. For example: A computer system is designed around as input device, a Central Processing Unit, an Output Device and a Storage Device. When linked together they work as a whole system for producing information. Fig. 1.1 [pic]

Fig. 1.1: Organization Structure

Interactions: Refers to the manner in which each component functions with other components of the system. Example: In computer system, the CPU must interact with Input Device to solve a problem. In turn, the Main Memory holds programs and data that the Arithmetic unit uses for computation.

Interdependence: Means that part of the organization in the computer system depend on one another. They are coordinated and linked together according to plan. One Sub-system depends on the input of another Sub-system i.e.: the output of one Sub-system is required input for another Sub-system. Fig. 1.2

Fig. 1.2: Task interdependence in a computer-based sub-system. Integration: Refers to the holism of systems. Integration is concerned with how a system is tied together, i.e.: parts of the system works together within the system even though each part performs a unique function.

Central objective: The objectives may be real or stated.
A stated Objective may be real objective. An organization can state one objective and operate to achieve another. Users must know the central objective of computer application early in the analysis for a successful design and conversion.

3. Elements of a system
1. Outputs and inputs.
2. Processor(s)
3. Control.
4. Feedback.
5. Environment.
6. Bouundaries and interface.

Outputs and Inputs
Inputs: Are the elements that enter the system for processing. Outputs: Are the outcome of processing.

Processor(s): They are elements of a system that involve the actual transformation of input into output. It is the operational component of a system.

Control: The control element guides the system. It’s the decision-making sub-system that controls the pattern of activities governing Input, Processing and Output.

Feedback: Control in dynamic system is achieved by feedback. Feedback may be positive or negative, routine or information.

Environment: The environment is the “suprasystem” within which an organization operates. It is the source of external elements that impinge on the system – determines how a system must function.

Boundaries and Interface: A system should be defined by its boundaries. The units that...
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