The British Broadcasting Corporation (BBC) in the UK was the first broadcaster to include closed captions (subtitles in the UK) in 1979 based on the Teletext framework for pre-recorded programming. It now offers a 100% broadcast captioning service across all 7 of its main broadcast channels.
Closed captioning (CC) and subtitling are both processes of displaying text on a television, video screen, or other visual display to provide additional or interpretive information.
Closed captioning of TV programmes made tv programmes accessible to deaf people. Most EU countries now have legislation that requires a percentage of all public programmes to have subtitles for deaf and hard of hearing.
The term "closed" (versus "open") indicates that the captions are not visible until activated by the viewer, usually via the remote control or menu option (teletext page 888, in most countries).
Both typically transcribe the audio portion of a program as it occurs (either verbatim or in edited form), sometimes including descriptions of non-speech elements. Other uses have included providing a textual alternative language translation of a presentation's primary audio language that is usually burned-in (or "open") to the video and unselectable.
The United Kingdom, Ireland, and most other countries do not distinguish between subtitles and closed captions and use "subtitles" as the general term.