AS - Digital Technology
- Created by: sballantine663
- Created on: 28-10-16 11:30
Internet
The Internet is a global communications system that links computers around the world.
Variety of Telecommunicatoions:
- Telephone Lines
- Satellites
Messages and Data:
These are sent from the source computer, through other computers until they reach the destination computer.
Computers can link to other computers by being attached to internet.
This can be achieved by:
- Common Technical standards
- Common Identification System
- Common Reference System
World Wide Web (WWW)
This is a collection of information that has grown up on a computer connected to the internet.
The information is:
- held in multimedia form
- stored in websites on web pages
Surfing = searching the web for information and following links to information
Uniform Resource Locator (URL)
This is a unique address referring to resources on the internet
Order of Components for URL
- 1- Protocol: http://
- 2- Domain Name: CCEA.org.uk
- 3- Filename: /DigitalTecnology
http:// and www. are assumed in URL so if you do not type them in the browser will put it in by default.
HyperText Transfer Protocol (HTTP)
This is a protocol that defines the process of identifying, requesting and transferring multimedia web pages over the internet.
Web Pages usually:
- are constructed using HTML
- have a secure variant of https in place
IP Address
The Internet Protocol Address uniquely identifies the physical address of a computer linked to the internet.
- Static IP Address: when computers have the same IP Address as they are always connected to the internet
- Dynamic IP Address: computers that have access to the internet through an ISP so are not always connected
Web Browser
This is an application running on a user's computer that is responsible for requesting the text and graphics of web pages from servers on the internet and assembling them for display.
Examples of Web Browsers:
- internet explorer
- mozilla firefox
- safari
- opera
- google chrome
Although all web browsers do the same task, they do not all have the smae set of features.
Web Server
This provides internet pages for other computers through the internet.
it often provides the cache of web pages which are stored when first accessed so they can be supplied later on without experiencing delay.
Web Hosting
This is a type of internet hosting service that allows individuals and organisations to make their website accessible, via the world wide web.
Web hosts are companies that provide space on a server owned or leased for use by clients. They also provide internet connectivity through a data center space.
File Transfer Protocol (FTP)
This is the most common protocol for the movement of files accross the internet.
How users get the file:
- Users can access a server holding the required file and request for it to be downloaded
- The user can send a file to a server that will accept uploads
Internet Service Provider (ISP)
This is an organisation that has direct links to the internet and accepts transmissions from users over dial up or broadband connections.
EXamples of ISPs:
- Sky
- BT
- EE
Search Engine
This is an application accessed over the internet that maintains the indexes of webpages.
How to use:
- A user will type in key words or phrases that they are searching for
- The search engine will compare this list with the pages in its index
- The search engine will then generate pages of hyperlinks that are relevant for the user to click on.
Cache
This is a store of recently accessed web pages, kept by a web browser.
If a user revisits a web page that is already stored in the cache, it can be loaded from the local copy, without needing access to the internet.
It will also save time loading webpages with logos as these logos are already downloaded so they do not have to download large data types again.
However if the user is trying to see an update in the web page, it will not appear as the cache will only reload identically to how it was on the last visit.
Cookies
Cookies are small files placed on the hgard drive of the user's computer by a website they have visited
They store personal information that will mean you will not have to re-enter information.
However you can block cookies as people have suspicions about what information is being gathered.
Portal
This is a website designed to be the one that a user will want to visit firstwhen accessing the web.
The site must offer services that the user needs regularly, such as search facilities, news updates, etc.
In most cases portal sites will allow the user to customise their pages to make it to what they want.
Advantage:
- can sell advertisin to companies for the page
Website
This is a collection of web pages with the same domain, often with similar themes and is usually maintained by a single individual or organisation.
The user navigates through a website using hyperlinks.
Webpage
This is a document accessed in a browser.
It can contain:
- text
- graphics
- audio
- video
Apart from text, these elements are not stored on the webpage, but are loaded into the page by the user's browser from the location specified by a Uniform Resource Identifier contained in a page.
For large data files streaming may be used.
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