Viewdata

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Information retrieval service and legacy system

title: "Viewdata" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["computer-network-technology", "history-of-computing-in-the-united-kingdom", "history-of-telecommunications-in-the-united-kingdom", "legacy-systems", "videotex"] description: "Information retrieval service and legacy system" topic_path: "technology/computing" source: "https://en.wikipedia.org/wiki/Viewdata" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Information retrieval service and legacy system ::

::data[format=table title="Infobox online service"]

Field	Value
name	Viewdata
title	Viewdata
image	File:viewdata Graphics 1.jpg
image_size	200px
caption	Viewdata Graphics used in the experimental phone directory of Post Office Telecommunications in 1977.
The image is a graphical representation of the Post Office/British Telecom Research laboratories (Adastral Park) in Suffolk, England. Note the "_ to continue" rather than the correct "⌗ to continue", showing a common rendering error.
developer	Samuel Fedida, Post Office
type	Videotex
launched
platform	Viewdata
::

::figure[src="https://upload.wikimedia.org/wikipedia/commons/e/ea/Teletext_Viewdata_Terminal.png" caption="A Viewdata machine displayed in [[teletext]] format"] ::

Viewdata is a Videotex implementation. It is a type of information retrieval service in which a subscriber can access a remote database via a common carrier channel, request data and receive requested data on a video display over a separate channel. Samuel Fedida, who had the idea for Viewdata in 1968, was credited as inventor of the system which was developed while working for the British Post Office which was the operator of the national telephone system. The first prototype became operational in 1974. The access, request and reception are usually via common carrier broadcast channels. This is in contrast with teletext.

Design

Viewdata offered a display of 40×24 characters, based on ISO 646 (IRV IA5) – 7 bits with no accented characters. Originally, Viewdata was accessed with a special purpose terminal (or emulation software) and a modem running at ITU-T V.23 speed (1,200 bit/s down, 75 bit/s up). By 2004, it was normally accessed over TCP/IP using Viewdata client software on a personal computer running Microsoft Windows, or using a Web-based emulator.

Keypad symbols: the sextile and the square

|name= Viewdata keypad symbols |mark=⌗ ⚹ |unicode=

|see also= |different from=

::figure[src="https://upload.wikimedia.org/wikipedia/commons/7/7c/Detail-Tastatur-FeTAp-751-1982.JPG" caption="Detail of a telephone keypad displaying the sextile and Viewdata square"] ::

::figure[src="https://upload.wikimedia.org/wikipedia/commons/d/d4/AVAYA_9611G_IP_Phone_detail_of_star_and_hash.jpg" caption="Detail of a more recent telephone keypad, in which (typographic) asterisk and number{{nbsp}}sign have replaced the ITU star and square"] ::

Viewdata uses special symbols already widely available on telephone keypads: the "star key" and the "square key", as formally recommended by the International Telecommunication Union. The ASCII asterisk (*) and number sign (#) are sometimes used instead because they are regular symbols on computer keyboards, although they do not match the ITU specification. On telephones, use of the number sign (hash symbol) has become the norm rather than the exception

These symbols appear as and in the Miscellaneous Symbols and Miscellaneous Technical Unicode blocks, respectively. The sextile was added due to its use in astrology, and the square had previously appeared in the BS_Viewdata character set, as a replacement for the underscore.

In 2013, the German national body submitted a Unicode Technical Committee proposal to align the Unicode reference glyphs with the ITU specifications for these symbols, and annotate them as telephone keypad symbols on the code charts. (Unicode 12.1), these changes have not been accepted/implemented.

Uses

Travel industry

As of 2015, Viewdata was still in use in the United Kingdom, mainly by the travel industry. Travel agents use it to look up the price and availability of package holidays and flights. Once they find what the customer is looking for they can place a booking. As of 2019, Viewdata is only used by a handful of travel agents.

Bulletin board systems

A number of Viewdata bulletin board systems existed in the 1980s, predominantly in the UK due to the proliferation of the BBC Micro, and a short-lived Viewdata Revival appeared in the late 1990s fuelled by the retrocomputing vogue. Some Viewdata boards still exist, with accessibility in the form of Java Telnet clients.

References

(1979-07-19). "Proceedings of the Videotex in Europe".
(2 February 2001). "E.161 : Arrangement of digits, letters and symbols on telephones and other devices that can be used for gaining access to a telephone network". [[International Telecommunication Union]].
Karl Pentzlin. (28 October 2013). "Proposal to incorporate two telephony symbols into Unicode by glyph and annotation changes".
(1981-06-01). "Alphanumerics for viewdata and broadcast teletext".
Unicode Consortium. "Miscellaneous Technical". The Unicode Standard.
"Agents vote for return of Viewdata in online poll".

::callout[type=info title="Wikipedia Source"] This article was imported from Wikipedia and is available under the Creative Commons Attribution-ShareAlike 4.0 License. Content has been adapted to SurfDoc format. Original contributors can be found on the article history page. ::