Talk:Viewdata

Quote "Source: from Federal Standard 1037C".

Yet, as far as I can tell, the word viewdata is not on the page which is quoted as a source.

Songwriter 07:16 6 Jul 2003 (UTC)


 * It isn't in the Wikipedia article but it is in the external link. Biscuittin (talk) 22:50, 22 December 2007 (UTC)

I have removed the earlybrowsers}} table as this has nothing whatsoever to do with viewdata systems. Also, more history of viewdata is available at the Prestel page. 87.81.12.15 (talk) 17:36, 17 August 2008 (UTC)

External links modified
Hello fellow Wikipedians,

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 * Added archive http://web.archive.org/web/20060303070521/http://haven.jml.net:80/ to http://haven.jml.net

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Colour check
Inspired by an article by Mr Samuel Fedida in the magazine Wireless World, William J. G. Overington, who had invented Telesoftware, designed an electronic artwork that could be displayed on a Viewdata page.

Mr Overington sent the design to Mr Fedida and Mr Fedida kindly arranged to have it keyed and then displayed on page 786 of the Viewdata system. Mr Overington viewed the design on a Viewdata equipped television set at the National Physical Laboratory (United Kingdom) in September 1977.

The design, upon a black background, was as if a block of red light at upper left, a block of green light at upper right (yet not the exact "upperness" value, it may have been higher or lower, possibly higher) and a block of blue light at lower centre, were all overlapping, so that seven colours appeared in the design. Namely yellow where the red block and the green block overlapped, white where all three blocks overlapped, magenta where the red block and the blue block overlapped, and cyan where the green block and the blue block overlapped.

Yet the three notionally overlapping blocks were not made solid colour, each block was made of some rows and some columns in which each character was the graphics version of a lowercase letter e thus the design consisted of lots of chunks of colour of two different sizes upon the black background.

Although designed to look as if three semi-filled rectangles, red, green, blue are overlapping, the design needed to have each of the areas encoded directly in the appropriate colour.

The design, in the teletext and viewdata format, is using lowercase letters e in graphics mode in seven colours. The design included eight different control codes, each a number of times. These eight control codes were the Hold Graphics control character and seven control codes of the form Graphics Colour, where Colour can be any one of Red, Green, Yellow, Blue, Magenta, Cyan, White.

Yet the way that the design was conveyed to Mr Fedida was not electronic.

Mr Overington had purchased from a stationery shop a notebook with ruled squares printed on each page; a notebook of the type used for exercises when initially learning arithmetic. A page was extracted from the centre, then a rectangle that enclosed twenty-four rows and forty columns was drawn upon it. This was to represent a Viewdata page, notwithstanding that each cell was square rather than rectangular.

A lowercase letter e was written in black where a lowercase letter e was to be keyed, and elsewhere letters were written in red to represent where the control codes were to be used. A legend explaining the meaning of each of the red letters was added below the design. The lowercase letters r, g, y, b, m, c, w were used for the seven Graphics Colour characters, and H was used for the Hold Graphics character. The Hold Graphics character was in one of the first few cells of each line that contained any "Graphics e" characters.

It would be interesting to know if the original paper design survives anywhere, and to know if the electronic version is archived somewhere and could be recovered, as both are part of the exciting times in the 1970s when teletext and viewdata were new technologies.

The 2021 graphic
A graphic, made in 2021 using the Affinity Designer program, is based, as best remembered, on the design of the Colour Check page that was displayed on page 786 of the Post Office's Viewdata system.

https://forum.affinity.serif.com/index.php?/topic/154847-colour-check/

Sextile symbol not rendering
Starting a topic to report a problem: That star-like symbol called the "sextile" isn't rendering for me on an Apple MacBook Air (M1, 2020) using both the latest Chrome and Firefox versions at the time of writing. Might need to use a kind of character encoding warning template like exists on linguistics pages. — AzureArmagedd0n (talk) 11:34, 26 September 2023 (UTC)


 * The "script" option recently added to unichar might provide a workaround? See template talk:unichar. 𝕁𝕄𝔽 (talk) 12:44, 26 September 2023 (UTC)
 * I'm not sure how one would use that to approximate a sextile. I'm very new to wiki editing so I'm quite unfamiliar with wiki templates and such. AzureArmagedd0n (talk) 05:03, 27 September 2023 (UTC)
 * More specifically, is there any font routinely available on MacBook that includes the sextile glyph? --𝕁𝕄𝔽 (talk) 13:21, 26 September 2023 (UTC)
 * I've no clue about that ¯\_(ツ)_/¯ AzureArmagedd0n (talk) 05:02, 27 September 2023 (UTC)
 * Short of copying the symbol into a document and then trying every font you have available until you find one? Then, pretending that the answer is Helvetica (most unlikely), try this: If that works with your selection, we can revise the article accordingly. A possible clue to finding the answer is astrology because the symbol  is used there too, so almost certain to feature on MacBooks. --𝕁𝕄𝔽 (talk) 09:38, 27 September 2023 (UTC)
 * I copied the symbol into the Font Book app and cycled through every system font but found no luck there. Would loading a web font be an appropriate solution? Perhaps maybe placing an svg in lieu of the character would work. AzureArmagedd0n (talk) 10:29, 27 September 2023 (UTC)
 * How strange. In that case, I'm afraid we just have to put up with it until the folks at Apple sort themselves out. An image of the symbol is already in the article, so I don't see that we really need another instance of it. (A web font would solve it for you but not for the other million MacBook users out there who wouldn't expect to have to install some special font first.) TBH, Viewdata is a very niche interest and very few people indeed will encounter it. But I've left a message at talk:Astrology since it is far more likely to be encountered there (sadly). --𝕁𝕄𝔽 (talk) 11:50, 27 September 2023 (UTC)
 * I am running a now older version of macOS (Monterey) so I can't speak for later versions which might have the symbol included but thanks for the quality follow-up regardless. AzureArmagedd0n (talk) 04:23, 28 September 2023 (UTC)