16-11-2012, 04:26 PM
System Analysis and Design
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Term system is derived from the Greek word ‘Systema’ which means an organized relationship among functioning units or components.
Definition of System
A system is an orderly grouping of interdependent components linked together according to a plan to achieve a specific objective.
Characteristics of a System
Organization
Interaction
Interdependence
Integration
Central Objective
Organization-It implies structure and order.
Interaction-It refers to manner in which each component functions with other components of the system.
Interdependence-Units/parts are dependent on each other.
Integration-The parts of a system work together within the system even though each part performs a unique function.
Central Objective-Objective may be real or stated. All the components work together to achieve that particular objective.
Elements of a System
Outputs and Inputs
Processor
Control
Feedback
Environment
Boundaries and Interface
Inputs and Outputs- Inputs are the elements that enter the system for processing and output is the result of processing.
Processor- It is the element that involves the actual transformation of input into output.
Control- The control element guides the system.
Feedback- Output is compared against performance standards.
Environment- It is the suprasytem within which an organization operates.
Boundaries and Interface- A system should be defined by its limits.
Types of System
Physical or Abstract System
Physical – These are tangible entities that may be static or dynamic in operation. For example- parts of a computer center are the desks, chairs etc. that facilitate operation of the computer. They are static and a programmed computer is dynamic.
Abstract System – These are conceptual or non physical entities. For example- the abstract conceptualization of physical situations. A model is a representation of a real or planned system. A model is used to visualize relationships.
Deterministic or Probabilistic System
Deterministic System – It operates in a predictable manner and the interaction between parts is known with certainty. For example: Two molecules of hydrogen and one molecule of oxygen makes water.
Probabilistic System – It shows probable behavior. The exact output is not known. For example: weather forecasting, mail delivery.
Social, Human Machine, Machine System
Social System- It is made up of people. For example: social clubs, societies
Human Machine System- When both human and machines are involved to perform a particular a particular task to achieve a target. For example:- Computer.
Machine System- Where human interference is neglected. All the tasks are performed by the machine.
Natural and Manufactured
Natural System- The system which is natural. For example- Solar system, Seasonal System.
Manufactured System- System made by man is called manufactured system. For example- Rockets, Dams, Trains.
Permanent or Temporary System
Permanent System- Which persists for long time. For example- policies of business.
Temporary System- Made for specified time and after that they are dissolved. For example- setting up DJ system.
Adaptive and Non Adaptive System
Adaptive System- respond to change in the environment in such a way to improve their performance and to survive. For example- Human beings, animals.
Non Adaptive System-The system which doesn’t respond to the environment. For example- Machines
Open System – It has many interfaces with its environment. It interacts across its boundaries, it receives inputs from and delivers outputs to the outside world. It must adapt to the changing demands of the user.
Closed System – It is isolated from the environmental influences. A completely closed system is rare.
Characteristics of Open Systems
Input from outside- Open systems are self adjusting and self regulating. When functioning properly open system reaches a steady state or equilibrium.
Entropy- Dynamic systems run down over time resulting in loss of energy or entropy. Open systems resist entropy by seeking new input or modifying the processes to return to a steady state.