Data exchange

Data exchange-

simplex- one way transmission only e.g computer to printer
half duplex-two way transmission but one way at a time e.g walkie talkie radios
duplex-two way transmission e.g telephone

Blog (simplex)
conference call (duplex)
instant message (half duplex)

the role of coder/decoder-
An electronic circuit that converts analog signals into digital signals and digital signals into analog signals. These are primarily used in teleconferencing applications.

Transmission networks-
fibre optic-
Optical fibers are widely used in fiber-optic communications, which permits transmission over longer distances and at higher bandwidths (data rates) than other forms of communication. Fibers are used instead of metal wires because signals travel along them with less loss.

the internet

                       The Internet

Global network...

A global network is any communication network which spans the entire Earth. The term, as used in this article refers in a more restricted way to bidirectional communication networks, and to technology-based networks

Connection methods...

Broadband- a high-capacity transmission technique using a wide range of frequencies, which enables a large number of messages to be communicated simultaneously.

Wi-Fi- a facility allowing computers, Smartphone, or other devices to connect to the Internet or communicate with one another wirelessly within a particular area.

Dialup internet service -is a service that allows connectivity to the internet through a standard telephone line. By connecting the telephone line to the modem in your computer and inserting the other end into the phone jack,

Server...

A network server is a computer designed to process requests and deliver data to other (client) computers over a local network or the Internet

Clients...

This is what your computer is called

Routers...

Allows you to connect to the server of your company.

World Wide Web

Web server...

The term web server can refer to either the hardware or the software that helps to deliver web content that can be accessed through the Internet. The most common use of web servers is to host websites, but there are other uses such as gaming, data storage or running enterprise applications.

What is the world wide web?

it is an information system on the internet which allows documents to be connected to other documents by hypertext links. enabling the user to search for information by moving from one document to another.

 

Hyperlink...

An element in an electronic document that links to another place in the same document or to an entirely different document. Typically, you click on the hyperlink to follow the link. Hyperlinks are the most essential ingredient of all hypertext systems, including the World Wide Web.

For example....

essential ingredient of all hypertext systems, including the World Wide Web.

Short for HyperText Transfer Protocol, the underlying protocol used by the World Wide Web. HTTP defines how messages are formatted and transmitted, and what actions Web servers and browsers should take in response to various commands. For example, when you enter a URL in your browser, this actually sends an HTTP command to the Web server directing it to fetch and transmit the requested Web page.

Search engines...

a program that searches for and identifies items in a database that correspond to keywords or characters specified by the user, used especially for finding particular sites on the Internet.

URL stands for Uniform Resource Locator. A URL is a formatted text string used by Web browsers, email clients and other software to identify a network resource on the Internet. Network resources are files that can be plain Web pages, other text documents, graphics, or programs.

URL strings consist of three parts (substrings):

1. network protocol
2. host name or address
3. file or resource location

 

 

 

 

 

 

 

 

 

 

Ubiquitous computing

Definition of ubiqiutous computing means existing or being everywhere at the same time

• Everyday objects online
• users may use many computational devices at the same time
• will enable diverse wireless applications including;
• monitoring pets
• the elderly
• housplants

Ubiquitous computing is global, local and social and personal.

Instant messaging

it is a real time conversation and its a way of communicating with people. the text is conveyed via computers connected over a networksuch as the internet.

people use IM because-

• you dont have to wait for an email response or a call to be returned
• IM chats are often very casual and more informal
• IM take multi-tasking to a new level. phone calls, web surfing and IM can all be done simultaneously.
• also its free

Steps

1. Download it
2. make an account
3. make a profile
4. add people
5. have your friends to add you to their lists
6. start chatting

Instant messaging on the web

Facebook
chatroom
SMS
emoticons

Security concerns

• basic common sense applies
• do not give personal info to strangers
• don not give imporant stuff uch as pin numbers.

IM culture

short messages
spelling mistakes
being informal

Abbreviations

LOL-laugh out loud
BRB- be right back
BTW-by the way
GTG-got to go
AFK- away from keyboard

Email and Protocol

Email-

• it is a method of exchanging digital messages from sender to one or more recipients. Todays email system is based on a store and forward model.
  


• the sender and recipients do not have to be online at the same time. your email waits in the inbox from anywhere around the world.
  


• address book- within an email you can include peoples names, email address etc.
  


• attachments- you can send things such as photos and videos.
  


• you can send the same email to multiple recipients. you can people in to the email using the CC (carbon copy) field. recipients who are in this field will be visible to everyone the email is sent to. however if you dont want other people to see that the email has been sent to them
  

Email format- 3 parts

• sender and recipient address 
  


• subject line
  


• body
  

Protocol-

• simple mail transfer protocol (SMTP)
  


• internet message access protocol (IMAP)
  


• post office protocol3 (POP3)
  

 

 

 

SMTP- it is a connection-oriented text based protoco. it communicates with a mail sender and mail receiver by issuing comands. the 3 steps are mail command to establish the return address, RCPT command to establish a recipient of the message and data to send the message.

 IMAP-  is a protocol for email retrieval. its an application layer internet protocol that allows an e-mail client to access email on a remote mail server. email clients using IMAP generally leave messages on the server until the user explicitly deletes them. Incoming e-mail messages are sent to an e-mail server that stores messages in the recipients e-mail box.

 POP3- is an application layer internet standard protocol used by local e-mail clients to retrieve e-mail from a remote server over a TCP/IP connction. pop supports simple download and delete requirements for access to remote mail boxes.