Extension Name of Some Files

A Website Window To Focus Upon Complete Computer Education

Windows Operating System

A Website Window To Focus Upon Complete Computer Education

Data Communication

A Website Window To Focus Upon Complete Computer Education

Some Abbreviations In Computer

A Website Window To Focus Upon Complete Computer Education

What Is The Internet

A Website Window To Focus Upon Complete Computer Education

Jan 18, 2013

DATA COMMUNICATION or DATA TRANSMISSION


DATA COMMUNICATION
Many organizations have multiple users of computers, some of these users are geographically remote from the organizations headquarter offices.Even within an office building, there may be hundreds or thousands of employees who use a particular computer.
Users have several options to choose from in communicating data
to and in receiving data from the computer.Data transmission may take place from a data terminal in one location to a data terminal in another location.In this case, both data terminals can be off-line to the computer or data transmission may be transmitted on-line to a computer from a remote data terminal or from another computer.


Data Communication



COMMUNICATION SERVICES
Normally an organization that wishes to transmit data users one of the common carrier services to carry the messages from station to station. Following is a brief description of these services.

1.Narrow Bands Services

Usually, this service is used where data volume is relatively low, the transmission rates usually range from 45 to 300 bits per second.

2.Voice Band Services

This service uses ordinary telephone lines to send data messages. Transmission rates vary from 300 to 4800 bits per second and higher.

3.Wide Band Services

Wideband services provide data transmission rates several thousand to several million bits per second.These services are limited to high volume users. Such services generally use coaxial cable or microwave communication.Space satellites, a more exotic development have been employed to rapidly transmit data from any part of the world to another part of the world. Communication services may be either leased or dialed up. A leased communication channel, which gives the user exclusive use of the channel is used where there are continuing data transmission needs. The dial-up variety requires the person to dial the computer (and of course the line may be busy), thus this alternative is appropriate for periodic data to transmit.

Transmission Modes 

Data transmission may occur in one of three modes ......

A> Simplex

Data is transmitted in one direction only the sending station cannot receive data.

B>Half Duplex

Data is transmitted back and forth between two stations.But data can only go in one of the directions at one point in time.

C>Duplex

Data can be transmitted simultaneously between two stations.Both stations can send and receive data at any point in time.

Jan 17, 2013

INTERNET CODE OF CONDUCT

CODE OF CONDUCT
The internet is based on co-operation of its constituents- users with users, service providers with other service providers and users and service providers with one another.
An internet society (ISOC) has developed the following guidelines of conduct ......

Advertising

1.Do not post to lists or boards or newsgroups whose purpose states no advertising.
2.Use browsing services such as WAIS, Gopher, and WWW to list products and services.
3.Use e-mail enabled information services like mailing lists to which users can subscribe or send the e-mail to obtain information.



Internet code of conduct


Mailing Lists, Newsgroups and Bulletin Boards

1.Avoid redundant, empty or stupid postings.
2.Post on to within the forum's topic or scope.
3.Respect the opinions of other participants.
4.Be careful about the lack of social sense and possible ambiguities in text communications.
5.Use common courtesy when posting critical, negative comments.
6.Be sensitive to forums standards in respect to indecency.
7.Do not use sexually harassing, racial or discriminatory expressions.

Privacy

1.Do not disclose the personal privacy of other users.
2.Do not forward e-mail without permission.
3.Do not deliberately break into computer systems.

Security

1.System breaking or helping others to break into systems is illegal.
2.Getting passwords or other access information is unacceptable.

Intellectual Property

1.Copying or disclosing copies of protected works without the author's permission is illegal.

Jan 15, 2013

COMPUTER NETWORKS

COMPUTER NETWORKS 
A computer network is a collection of computers terminal devices connected together by a communication system. The set of computers may include large-scale computers, medium-scale computers, minicomputers, and microprocessors.

The set of terminal devices may include intelligent terminals, "dumb" terminals, workstations of various kind and miscellaneous devices. 


FEATURES

1. Share resources from one computer to another.
2. Create files and store them in one computer, access those files from the other computers connected to the network.
3. Connect a printer, scanner or a fax machine to one computer within the network and let other computers of the network use the machines available over the network.



Computer Networks


    Following is the list of hardware required to set up a computer network .............

A>NETWORK CABLES :
Network cables are used to connect computers.the most commonly used cables are category 5 cable RJ-45.

B>DISTRIBUTORS :

Each and every computer can be connected to another one via a serial port but if we need to connect many computers to produce a network, this serial connection will not work.The solution is to use a central body to which other computers, scanners etc.Can be connected and then this body will manage or distribute network traffic.

C>ROUTER :

A router is a type of device which acts as the central point among computers and other devices that are part of a network.a router is equipped with holes called ports.Computers and other devices are connected to a router using network cables.Nowadays router comes in wireless modes using which computers can be connected without any physical cable.

D>NETWORK CARD :

The Network card is a necessary component of a computer without which a computer cannot be connected to a network.Also known as network adapter or network interface card.Most of the branded computers have network card pre-installed.Network cards are two types internal and external network cards.

                  INTERNAL NETWORK CARDS   

The motherboard has a slot for internal network card where it is to be inserted.Internal network cards are of two types.The first type uses peripheral component interconnect(PCI) connection.The second type uses industry standard architecture(ISA).Network cables are required to provide network access. 

                 EXTERNAL NETWORK CARDS    

Comes in two flavors. Wireless and  USB based.Wireless network card needs to inserted into the motherboard but no network cable is required to connect to the network.USB card is easy to use and connect via USB port.The computer automatically detects USB card and can install the drivers required to support the USB network card automatically.

TYPES OF NETWORKS

There are many types of networks.However, from an end- user's point of view, these are of three basic types.The three basic types of computer networks are as follows .......

1.Local Area Network(LAN)

In this types of network, the different nodes are at most 1KM apart. Generally, LAN is preferred for short distance communication. e.g., between two rooms of the same building or within the same company premises.
Example- Novell Network.

2.Wide Area Network(WAN)

Here, the different nodes are geographically far apart from one another, separating two cities or two states or even two continents. The method of communication in WAN is through logical channels. Actually, the origin of WAN was from ARPANET(advanced research project agency network).
Example- Internet.

3.Metropolitan Area Network(MAN)

A metropolitan area network is larger than a LAN. Its features are similar to both LAN and WAN. It is called metropolitan since it normally covers the area of a city.Different hardware and transmission media are often used in MANs because these must efficiently cover the distance(a few tens to about one hundred kilometers) or because these do not require complete access to locations between the network sites.
Example- Cellular Phone, Pager etc.

In addition to these types, the following characteristics are also used to categorize different types of the network.


TOPOLOGY

Topology is the geometric arrangement of a computer system. common topologies include a bus, star, ring etc.

PROTOCOL

The protocol defines a common set of rules and signals used by computers on the network to communicate. One of the most popular protocols for LANs is called Ethernet.Another popular LAN protocol for PCs is the IBM token ring network.

ARCHITECTURE

Networks can be broadly classified as using either peer-to-peer or client/server architecture.Computers on a network are sometimes called nodes.Computers and devices that allocate resources for a network are called servers.

BUS

In computer terminology, a bus is a circuit that carries data from one component to another.




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