Structured System Analysis and Design: System Concepts:

1. Structured System Analysis and Design:System Concepts:

2. Topics Covered: • System • Sub system • Characteristics of System • Elements of Systems • Types of System • Physical and Abstract System • Deterministic and Probabilistic System • Open and Closed System • Man made Information System

3. System: A set of components that work together to achieve a goal by: • Accepting inputs • Processing it • Producing outputs in an organized manner. • Examples:Computer System, Education System, Production System, Transportation System etc.

4. Sub System: Each system is composed of sub systems. The lowest level subsystem is called Black box system. • The subsystems are integrated to form a system because a full system is too large to analyze. Sub system A Sub system B Sub system C Inputs Output from A Output from B Outputs Input to B Input to C

5. Characteristics of a System: • Specific Objective: e.g. Business system has profit making as its objective or goal. • Components: Subsystems which collectively work to achieve goals of the system. • Organization: Arrangement of components that helps to achieve objectives.

6. e.g. General arrangement of a computer has • An input device • A CPU • An output device • One or more storage units • These work together as a computer system.

7. Interaction: e.g. In an organization purchasing interact with production, advertising with sales and payroll with personnel. • Interdependence:e.g. One subsystem depends on the input of another subsystem for proper functioning. Output of the one subsystem is the required input for another subsystem. • Integration: It means that parts of the system work together where each part (component) performs a unique function. • Behavior:A system responds according to its environment. E.g. a person may look left and right before crossing a road.

8. Elements of a System: • Outputs: The main objective of a system is to produce outputs. Therefore first of all we must determine goal or purpose of work. • Inputs: Inputs are the elements that are entered into the system for processing. Inputs can be easily determined if outputs are known.

9. The characteristics of inputs are: • Accuracy • Timeliness • Proper Format • Economy

10. Processor: This is the operational component. It converts inputs to outputs. Processor may totally or partially modify the input depending upon the specifications of outputs. • Control: The decision maker element that control the activities of the system This element makes the system to operate within tolerable performance levels. • Feedback: Feedback provides information about system performance and thus required modifications. It is of 2 types: Positive: Routine in nature & increases performance Feedback Negative: Provides information for action

11. Environment: The external elements which have an effect on the system forms an environment. e.g. An organization’s environment may consist of vendors, competitors, banks, government and others. • Boundaries and Interface: limits that identify system’s components, processes and interrelationships when it interfaces with another system. • e.g. A teller system in bank may include deposits, withdrawals etc. but may exclude mortgage, trust activities.

12. Types of system: • Physical and Abstract system: • Physical systems are tangible entities that may be static or dynamic in operation. e.g programmed computer is dynamic whereas tables, chairs, monitor etc are static. • Abstract systems are conceptual or non physical entities e.g A model which is a representation of real system is an abstract system .

13. Deterministic and Probabilistic system: • A Deterministic system is one in which occurrence of all events can be perfectly predicted. e.g a computer program. • A Probabilistic system is one in which occurrence of all events can not be perfectly predicted. e.g contents of a stock.

14. Open and Closed system: • An Open system is one which interacts with its environment being able to receive unexpected inputs. e.g Business Organization. • A Closed system is one which does not interact with its environment. Such systems are rare e.g A computer system is not really but relatively closed system.

15. Man made Information system: • Informationsystem is defined as interaction of man & machine which gathers data & provides information after analysis. Management can take decision based on information system. The major information systems are: • Formal Information system • Informal Information system • Computer based Information system

16. Formal Information system: It is based on the organization represented by the organization chart. It provides 3 types of information • Strategic Information • Managerial Information • Operational Information Top Middle Lower Strategic Information Managerial Information Operational Information

17. Informal Information system: It is an employee based system designed to meet personnel and vocational needs. • Computer based Information system: This information system depends on the computer for handling business application. It is classified as: • Transaction Processing System: • Management Information System:

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