Database

Database

A database is a collection of data, or information, specially organized for rapid search  and retrieval by a computer. It consist of a file or a set of file; the information in these files may be broken down into records, each of which consist of one or more fields. A field contains information pertaining to one aspect or attribute of the entity.

Data Transmission Mode

Date is transmitted in three mode:

simplex transmission permits communications over a channel in only one direction.

Half duplex transmission permits two way communication over a channel, but data is transmitted in only one direction at a time, for example acb radio

Full duplex transmission permits simultaneous communication over a channel for a example a telephone line.

The term Boud is derived from Boudot the Frenchman who developed a telegraph communications.

Modems

It's device that convert the analogue in digital signal. Modem communicate which each a cross a telephone lines. Modem convert the digital signal in a analogue signal when a computer send information, instead it convert the analogue signal in digital when the computer has to receive an information.

The word "modem" is a contraction of two word: modulator and demodulator.

Virus

The virus is a buggy program that infect your network. The virus damages the files and to avoid to lose all the programs is used an antivirus.

Network and Networking Terminology

A Network consist of software and various hardware device, that are physically connected to share resources, like:

Information

Printers

Processing power

Host is a unique name of each computer. But you must have a name that is user-name and when you want to use a computer you must identify (log-in) yourself through a user-name and password.

Network Topologies

Bus Topology: connects each node with a single cable. It's sometimes referred to as point to point communication.

Ring Topology: connects each node with a direct communication; each node is a connected to two other node. Is use in large university.

Star Topology: in this topology the node are connected among them through a central hub and therefore all the computers pass in the central computer (host) when they have to communicate.

Hybrid Topology: two or more types of topologies.

Internet

The internet is a global network of computers that allows many millions of computer users to share and exchange information. With internet you can also read for example e-mail from another computer in another country.

Provider is a company organization that provides service. Such us a company that provide cellular phone service to mobile phone users (ISP = Internet Service Protocol)

The Internet Toolbox

FTP: using the process called File Transfer Protocol you can retrieve any file from a distant computer and transfer it to your hard disk (this process is called "downloading a file").

E-MAIL: is an electronic mail that is a paperless method of communicating and storing messages using a computer, in fact with e-mail you can send messages to other people that are in Internet.

WWW: is a acronym of World Wide Web and it's a hypertext-based system for finding and accessing information on the Internet. The Web as it is usually called, is a universe of "linked" pages. WWW is the brainchild of CERN engineer Tim Berners-Lee.

Hypertext: each pages on the Internet is a hypertext document. This term is coined by Ted Nelson. In practice, it means that a piece of text within one document may have a link to other pieces of text, either within the same document or on an external document.

HTML: it's a programming language developed during the 1980s and on this language is based the Web

Node: is a point on network through which a device, such as a workstation, a printer, a fax, or a file server is linked to the network.

LAN - WAN

LAN: is the acronym Local Area Network and it's a combination a two on more personal computers or workstation that are physically and logically connected to each other. The LAN is used for allowing to a group of user to share the data or the programs. The redoubts dimensions allow a notable speed the transmission and receipt of the data 

WAN: is the acronym Wide Area Network and it's a network interconnected to another network in other parts of a building or the other parts of the country.