WJEC GCSE Computer Science Unit 1 Internet Hardware and Compression

Objectives To describe how data is sent over the Internet including: The hardware necessary to connect to the Internet Common File Standards associated with the Internet Compression Techniques such as Lossy and Lossless compression To explain the difference between the Internet and the World Wide Web

The Internet and the World Wide Web The World Wide Web (www) is the name given to the vast collection of web pages which are stored on the Internet. The Internet is the underlying infrastructure; a worldwide collection of connected computer networks (WAN).

Hardware needed to connect to the Internet Most computer systems use a modem to connect to the Internet. A modem, the abbreviation of modulator/demodulator, is a device which allows digital computer systems to communicate over analogue systems, most commonly the telephone network. Traditionally, whilst a modem was in use, the telephone line would be unavailable to make telephone calls. Broadband modems were later released which allowed for faster data transfer and would also allow users to make telephone calls over the same line at the same time.

Hardware needed to connect to the Internet A third common type of hardware used to connect to the Internet is a media converter, which allows computer systems to connect to the Internet using fibre optic cable. Typical data transfer speeds Modem: 56.6 Kbps Broadband modem: 8 – 24 Mbps Fibre optic: 100 Mbps

Common file standards associated with the Internet

Workbook Complete section 5 Q1-2

Compression Compression is the process of making a file size smaller. This may be advantageous as it allows more data to be stored on the disk and files may also be transferred more quickly. There are two primary methods that are used to compress files stored on a computer system; these are lossy and lossless.

Lossless Compression Lossless compression uses an algorithm that compresses data into a form that may be decompressed at a later time without any loss of data, returning the file into its exact original form. It is preferred to lossy compression when the loss of any detail, for example in a computer program or a word-processed document, could have a detrimental effect.

Lossless Compression A simplified version of lossless compression on a word-processed document may to be to replace a common string, such as ‘the’, with a token such as the symbol @. One character takes 1 byte of memory. Therefore, the string ‘the’ would take 3 bytes.

Lossy Compression Lossy compression is a data compression technique that compresses the file size by discarding some of the data. The technique aims to reduce the amount of data that needs to be stored.

Lossy Compression Lossy compression is also used to compress multimedia data, such as sound and video, especially in applications that stream media over the Internet.

Workbook Complete section 5 Q3