The control codes of the 1976 teletext specification are a brilliant solution, given the boundary condition

[William_J_G Overington]

In the document

https://www.unicode.org/L2/L2022/22013-c0-c1-stability.pdf

Kent Karlsson writes:

> But there are some character encodings that are “a bit crazy” when it 
> comes to control codes. They override all of C0 (or C1) with something 
> that cannot even be regarded as pure control characters. In particular 
> Teletext ...

In my opinion, the control codes of the 1976 teletext specification are 
a brilliant solution, given the boundary condition that existed at the 
time.

In order to work, a teletext-equipped television set needed enough solid 
state memory, to which data could be wriiten and from which data could 
be read, to store a whole teletext page.

At the time such solid state memory was expensive, so using two 
kilobytes of memory rather than one kilobyte of memory would have added 
significant cost to each teletext-equipped television set.

So the decision was made to design the specification such that one 
kilobyte of solid state memory would be sufficient to store a complete 
teletext page.

I was told that originally the BBC (British Broadcasting Corporation) 
and the IBA (Independent Broadcasting Authority) had each developed a 
prototype system of a text-based information system of its own and that 
the best features of each were included in the agreed common teletext 
technical specification.

In an era where personal computing was only starting and computers were 
mostly in businesses, universities and polytechnics, and mostly in 
monochrome and just text-based, colourful teletext with its graphics was 
very futuristic and often on view displaying a multipage (a teletext 
page on a fixed page number yet such that there were a number of 
different page displays broadcast in sequence, changing, say, every 
thirty seconds) in the window display of a shop.

William Overington

Wednesday 12 January 2022