Teletext is a 40
column by 25
line standard for broadcasting
textual information alongside a
television signal. The "
carousel" (meaning all the pages being transmitted) is broken up into "
magazines" (being a set of pages with the same initial digit). Each page within a magazine has a three digit identifier, with "x00" being the magazine index.
To enable articles to span more than a single screenful, pages are made up of "frames", all with the same page number but a different "subpage" number. For example, Lloyds TSB shares might be on BBC2 Ceefax page 222, subpage 0002.
Each cell can contain an alphanumeric character, a graphic character or a control code.
Graphic characters are based on a 3 high by 2 wide grid (with the grid elements either solid or "separated").
Control codes are things such as "red", "set background", "double height", "white", "hidden", etc.
The same display standard is used in Viewdata, which has fallen by the wayside of computer history.