The Internet

The Internet is a world-wide network of computer networks, web pages and hyperlinks.

It is the most commonly used network in the world.

MODEM - Allows the computer to connect to the internet.

ROUTER - Connects a computer network to the internet via a standard telephone line

ISP (Internet Service Provider) - Companies which provide access to the internet. Examples include Sky, Virgin Media and BT Internet.

IP Addresses are unique numbers that allow computers to communicate with each other from anywhere via the internet.

Static IP Addresses are permanently assigned to each computer. They reveal information such as the continent, country, region and city a computer is located in. 

DNS (Domain Name System) translates names into 12 digit IP addresses. When you search a domain name such as www.getrevising.co.uk, the DNS will search through a table of names linked to their IP addresses so that when www.getrevising.co.uk is found, the DNS can translate the domain name into its IP address.

If the domain name cannot be found on one DNS server, it will move onto another until the name is found.

Hyper Text Markup Language (HTML) is the language used to develop websites. When a webpage is loaded, HTML is used to show and enable content such as (rollover) images, text, sound, videos and other features. It also informs the browser of the whereabouts of other related multimedia.

Hyper Text Transfer Protocol (HTTP) is added at the front of any domain name. It is used to request and deliver web pages from the internet. 

1) User types in browser name.

2) DNS converts this to IP address.

3) Browser has the IP address and sends http get command to the web server.

4) Web server returns HTML data stream.

5) Web browser renders HTML web page, showing all the element coded into the website.

JPEG (Joint Photographic Experts Group) is a compressed bitmap image file used commonly for photographic purposes. The compression size can be chosen.

GIF (Graphics Interchange Format) is a lossless bitmap image file used for photographs with a small amount of colours. GIF images can be played in a sequence to form a simple animation.

PDF (Portable Document Format) is a universal file standard used to read and exchange files. Files are in their exact original format, and many applications are developed to be able to create and view PDF files.

MP3 (Moving Pictures 3) is a lossy audio file format used primarily in the distribution of music across the internet. It uses lossy compression to reduce the file size, so the quality of sound can be decreased when compressed.

MPEG (Moving Pictures Experts Group) is a format used to view and encode audio/visual information. Lossy compression is used for both audio and visual components.

File compression is used when transmitting files over the internet. It is done through encoding information using fewer bits so that less data is being transmitted. As a result, files may be of lower quality because less data is encoded.

Compressing files has its advantages:

• Reduces file storage
  
• Reduces traffic
• Faster download/upload speeds
• Faster web page viewing

However, it also has its disadvantages:

• Reduces file quality
• Some elements of a file may not be viewed as were intended

Lossless compression is where no elements of the data is lost during transmission. It does this by searching for patterns within data.

Text files are examples of lossless compression because they have lots of patterns within the data. Letters are often next to each other, which is an example of patterns within the data.

Lossy compression is where certain elements of the data are lost during transmission. This is because there is unique data which means there are little patterns in the data. If the quality of the file after transmission with lossy compression is acceptable, then lossy compression will take place. 

Audio files are examples of lossy compression because they have little repeated data so there aren't as many patterns as there are in a text file.