AS Web Applications

The internet is a global communications system linking computers in geographically seperate locations. It can be done using a variety of telecommunications such as:

• Telephone Lines
• Satellites

It allows for fast communications between computers or other devices such as:

• Mobile Phones
• PDA's

Messages and data are passed from the source computer, through other computers until the destination computer is reached.

The WWW is a collection of information that has grown up on computer connected to the internet. This information is held in multimedia form and is stored in locations called websites in the form of web pages.

The process of searching the web is known as surfing.

A URL is a unique adress for refering to resources on the internet. The main components in order are:

• Protocol
• Domain Name
• Filename of any extension required

AN example of a URL is:

http://CCEA.org.uk/DigitalTechnology.html

HTTP is a protocol that defines the process of identifying, requesting and transferring multimedia web pages over the internet. These web pages are usually constructed using HTML and a secure variant HTTPS exists.

A physical address of each computer linked to the internet. The domain name server converts the domain name to its corresponding IP address. An IP address consists of 4 numbers seperated by full stops. There are static and dynamic IP addresses. An example of an IP address is:

158.152.1.58

A web browser is an application running on a users computer that is responsible for requesting text and graphics of web pages from servers on the internet. Examples of web browsers are:

• Google Chrome
• Opera
• Safari

A web server provides internet pages for other computers through the internet using HTTP. It often provides a cache of web pages stored when they are first accessed to be supplied later without any delay of accessing the internet.

A hosting service allows individuals or organisations to make their website accessible to the world wide web. Companies provide space on a sever owned or leased for use by the client for a set fee.

FTP is a common protocol for the movement of files across the internet. It is a way that most personal web pages are delievered to the web server where they are stored. Passwords and usernames are frequently required.

This is an organisation that provides services for accessing the internet. It accepts transmissions from users and thus passes these onto the internet. Examples of ISP's are:

• BT
• Sky
• TalkTalk

This is an application accessed over the internet that maintains indexes of web pages. It searches for information on the world wide web. This generates a list of hyperlinks which the user can click on. Examples of search engines are:

• Google
• Bing

A store of recently accessed web pages which can be loaded by a local copy rather than accessing the internet. Cache memory is usually found close to the processor so that it loads faster on the users screen.

These are small files placed on the hard drive of the users computer. On a subsequent visit of a web page visited before, personal information they have previously entered doesn't need to be requested again. this saves time for the user, however, they may not want to use it due to the hard drive space it takes up.

A portal is a website designed to be the one that a user will want to visit when accessing the web. There are obvious commerical advantages for a portal in attracting as many users as possible as they can sell advertising on the site.

A portal site, in most cases, allows the user to customise their own page. For example, they may choose to see news headlines which cater to the users intrests.

A website is a collection of web pages at the same domain, often with a common theme and are usually maintained by a single user or organization. The user moves between pages by clicking hyperlinks. This cause a new page to be loaded, or parts of the page to be refreshed.

A web page is a 'document' accessed in a browser. It generally contains text and images but it may also contain a video or audio. They are loaded onto the page by the users browser from the location specified by the URL.