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Tuesday, January 30, 2018

Types of Systems

The systems can be divided into the following types:
 
Physical or Abstract Systems

  • Physical systems are tangible entities. We can touch and feel them. Physical System may be static or dynamic in nature. For example, desks and chairs are the physical parts of computer center which are static. A programmed computer is a dynamic system in which programs, data, and applications can change according to the user's needs.

  • Abstract systems are non-physical entities or conceptual that may be formulas, representation or model of a real system. 

Open or Closed Systems
 
  • An open system must interact with its environment. It receives inputs from and delivers outputs to the outside of the system. For example, an information system which must adapt to the changing environmental conditions.

  • A closed system does not interact with its environment. It is isolated from environmental influences. A completely closed system is rare in reality.

Adaptive and Non Adaptive System

  • Adaptive System responds to the change in the environment in a way to improve their performance and to survive. For example, human beings, animals. 
  • Non Adaptive System is the system which does not respond to the environment.For example, machines.

Permanent or Temporary System
  • Permanent System persists for long time. For example, business policies.
  • Temporary System is made for specified time and after that they are demolished. For example, A DJ system is set up for a program and it is dissembled after the program.

Natural and Manufactured System
  • Natural systems are created by the nature. For example, Solar system, seasonal system.
  • Manufactured System is the man-made system. For example, Rockets, dams, trains. 

Deterministic or Probabilistic System
 
  • Deterministic system operates in a predictable manner and the interaction between system components is known with certainty. For example, two molecules of hydrogen and one molecule of oxygen makes water.
  • Probabilistic System shows uncertain behavior. The exact output is not known. For example, Weather forecasting, mail delivery.

Social, Human-Machine, Machine System
 
  • Social System is made up of people. For example, social clubs, societies.
  • In Human-Machine System, both human and machines are involved to perform a particular task. For example, Computer programming.
  • Machine System is where human interference is neglected. All the tasks are performed by the machine. For example, an autonomous robot.


Man–Made Information Systems
  • It is an interconnected set of information resources to manage data for particular organization, under Direct Management Control (DMC).
  •  This system includes hardware, software, communication, data, and application for producing information according to the need of an organization. Man-made information systems are divided into three types:

  •  Formal Information System: It is based on the flow of information in the form of memos, instructions, etc., from top level to lower levels of management.
  • Informal Information System: This is employee based system which solves the day to day work related problems.
  •  Computer Based System: This system is directly dependent on the computer for
managing business applications. For example, automatic library system, railway
reservation system, banking system, etc.

Properties of a System

Properties of a System

A system has the following properties:
 
Organization
Organization implies structure and order. It is the arrangement of components that helps to achieve predetermined objectives.


Interaction
It is defined by the manner in which the components operate with each other. For example, in an organization, purchasing department must interact with production department and payroll with personnel department.


Interdependence
Interdependence means how the components of a system depend on one another. For proper functioning, the components are coordinated and linked together according to a specified plan. The output of one subsystem is the required by other subsystem as input.


Integration
Integration is concerned with how a system components are connected together. It means that the parts of the system work together within the system even if each part performs a unique function.


Central Objective
The objective of system must be central. It may be real or stated. It is not uncommon for an organization to state an objective and operate to achieve another. The users must know the main objective of a computer application early in the analysis for a successful design and conversion.
 

What is a System?

What is a System?
The word System is derived from Greek word Systema, which means an organized relationship between any set of components to achieve some common cause or objective. A system is “an orderly grouping of interdependent components linked together accordingto a plan to achieve a specific goal.”
Constraints of a System
A system must have three basic constraints:
1. A system must have some structure and behavior which is designed to achieve
a predefined objective.

2. Interconnectivity and interdependence must exist among the system components.
3. The objectives of the organization have a higher priority than the objectives of its subsystems.

For example, traffic management system, payroll system, automatic library system,
human resources information system.

Thursday, November 30, 2017

Frequency Spectrum


Band
Range
Uses
Very Low Frequency(VLF)
3KHz-30KHz
Long range Radio Navigation
 Low Frequency(LF)
30KHz-300KHz
Radio Beacons
Medium Frequency(MF)
300KHz-3MHz
AM Radio
High  Frequency(HF)
3MHz-30MHz
Citizen Band(CB)/Ship/Aircraft Communication
Very High Frequency(VHF)
30MHz-300MHz
VHF TV, FM Radio
Ultra High Frequency(UHF)
300MHz-3GHz
UHF TV, Cellular phones
 Extremely High Frequency(EHF)
3GHz-30GHz
Satellite communication
Superior High Frequency(SHF)
30-GHz-300GHz
Radar, Satellite

Wireless Media



  It is also known as a wireless media. Wireless media transmit and receive electromagnetic signals without and electrical or optical conductor.  Here transmission and reception achieved by means of an antenna. For transmission antenna emits signal into medium and for reception antenna picks up electromagnetic signals from the surrounding medium. The two forms of transmission:
  Directional: - In this, transmitting antenna puts out a focused electromagnetic beam. The transmitting receiving antenna must be aligned, known as Point-to-Point Communication.
   Omni-directional: - In this the transmitted signal spreads out in all direction and be received by many antenna inspite of direction.
According to frequency range the wireless media is divided into three parts:-
·         Radiowave (30MHz-1GHz): Omni directional transmission
·         Microwave (1-40GHz): Point-to-Point Communication
·         Infrared (100GHz-1000 THz light frequencies): Local Point to Point, Multipoint application within confined areas.

Cable Transmission Media Comparison



Cable Transmission Media Comparison

Media
Cost
Ease of Installation
Capacity Range
Attenuation
Immunity from Interference
Unshielded Twisted Pair
Extremely Low
Very simple
1 to 100 Mbps
High, maximum effective range in 100s of meters
Low
Shielded Twisted Pair
Moderate
Simple to moderate
1 to 155 Mbps
High, maximum effective range in 100s of meters
Moderately low
Coaxial cable
Low to moderate
Simple
Varies by size and composition between 1 Mbps to Gbps
High, maximum effective range in low Kms
Moderate
Fiber Optic Cable
Moderate to high
Difficult
10 Mbps to Gbps
High, maximum effective range in 10s of Kms
High

Types of Systems

The systems can be divided into the following types:   Physical or Abstract Systems Physical systems are tangible entities. We can touc...