Technical Glossary -- (Kurt Smith)

compact disk

"(Compact Disc Read-Only Memory). Like music CDs, but may contain information in the form of text, graphics, sound and moving video that can be accessed through a computer. A CD-ROM can store as much information as around 450 floppy discs.",

compact disk recordable

compact disk re-writeable

Real time conversations on the Internet, can occur on the world wide web, Internet relay chat (IRC), through instant messaging, on-line commercial servers (eg AOL or CompuServe). Can be accessed through websites. A chat room is an on-line forum where two or more people can engage in chat (Careaga).

Checksum is a code used to verify data. It is created by performing a mathematical operation on all the data together, and will change according to the value of the data.

Checksums are used to make transmitted data is correct. When sending data, the transmitter calculates the checksum of the data that is sent, and sends it with the data. The receiver also calculates the checksum of the data it receives. If the checksums don't match then the data�must be�different - i.e. it has not been�correctly transmitted�- and needs to be re-sent.

cHTML (Compact HTML) is effectively a cut down version of the regular HTML (Hypertext Markup Language) used over the Internet, which has been adapted for use with small computing devices such as personal digital assistants (PDAs), mobile phones, and smartphones. cHTML enables small handheld devices to connect to the World Wide Web, and to present Internet text content on the mobile device's display screen.

Because handheld devices have limitations in their display, power supply, and memory resources, cHTML does not support JPEG images, tables, image maps, multiple fonts, background colours and images, frames, style sheets and more than two colours. As pages are designed to fit the screen, scrolling is also not featured, but four buttons are used to do all the basic operations. However, cHTML does support GIF images.

WML (Wireless Markup Language) is a similar markup language used with the WAP (Wireless Application Protocol). cHTML was originally developed for use with i-Mode devices by Access Company Ltd., a Japanese company, and was accepted by the W3C in 1998.

Churn is a term referring to customer turnover. The word churn is used to describe those customers abandoning a service or product, and it is particularly applied to Internet and cell-phone subscribers, who tend to often switch providers as a result of intense competition. Churn rate is calculated as the number of customers lost over a time period, divided by the average total number of customers during that period.

For commercial reasons providers will be anxious to understand why the churn rate is high, and whether it is due to customer dissatisfaction with the price or type of services offered. Some providers even offer special deals of free equipment or an initial charge-free period to attract new customers. Also, to discourage churn, the customer may be asked to sign a service agreement containing penalty clauses, to ensure that they stay with the provider for a minimum period

CIF (Common Intermediate Format) describes a video resolution that is a quarter of the television drawing area. Whilst this should strictly mean 352 x 288 pixels for PAL (used primarily in Europe) and 352 x 240 pixels for NTSC (American) resolutions, the convention of 352 x 288 pixels tends to be globally adhered to by mobile phone manufacturers when describing their screens or cameras.

The acronym CIF was originally brought in to use in the late eighties to early nineties by video conferencing applications but is rarely heard these days as the resolution it describes is relatively small and uncommon, only being used in the context of VideoCD, and more recently mobile phones and low end digital cameras. Common Interchange Format is sometimes also known as D1.

Circuit switching (Line Switching) is a method of transmitting information (voice, video or other streamed data) between endpoints within telecommunications systems. Each individual subscriber is allocated a dedicated channel of constant bandwidth, which must be maintained open for the duration of their call, even if no actual conversation is taking place and no data being transferred.

Circuit switched systems were used in the old fixed landline telephone networks, for point-to-point connections routed directly between terminals. However, circuit switching may still be the best option when uninterrupted large file transfers need to be sent, or for long voice calls and videoconferencing, but it seems to be mainly suitable for voice traffic. Circuit switching can be considered as the opposite approach to packet switching, which does not require a dedicated channel, and makes more efficient use of the network's resources.