Viewdata

Viewdata offered a display of 40×24 characters, based on ISO 646 (IRV IA5) – 7 bits with no accented characters.{{cite web| url=http://aei.pitt.edu/94572/1/videotex.pdf | title=Proceedings of the Videotex in Europe | access-date=2023-12-26 | date=1979-07-19}}

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.

{{Infobox symbol

|name= Viewdata keypad symbols

|mark=⌗ ⚹

|unicode={{unichar|2317||html=}}
{{unichar|26B9|html=|nlink=}}

|see also=

|different from={{unichar|002A|html= | nlink= }}
{{unichar|0023|html= | nlink=}}

}}

File:Detail-Tastatur-FeTAp-751-1982.JPG

File:AVAYA 9611G IP Phone detail of star and hash.jpg

Viewdata uses special symbols already widely available on telephone keypads: the {{key press|⚹}} "star" key and the {{key press|⌗}} "square" key, as formally standardised by the International Telecommunication Union.{{cite web | url = http://www.itu.int/rec/T-REC-E.161-200102-I/en | title = E.161 : Arrangement of digits, letters and symbols on telephones and other devices that can be used for gaining access to a telephone network | publisher = International Telecommunication Union | date= 2 February 2001 | access-date = 23 December 2019}} These are often treated as approximately corresponding to the ASCII asterisk (*) and number sign (#), which do not necessarily conform to the ITU specifications for the keypad symbols; the asterisk is also usually displayed smaller and raised.

These symbols appear as 'Sextile' and 'Viewdata square' in the Miscellaneous Symbols and Miscellaneous Technical Unicode blocks, respectively. The sextile was added due to its use in astrology,{{cite web|url=https://unicode.org/L2/L2013/13105r-telephony.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://unicode.org/L2/L2013/13105r-telephony.pdf |archive-date=2022-10-09 |url-status=live | title= Proposal to incorporate two telephony symbols into Unicode by glyph and annotation changes | date= 28 October 2013 | access-date = 23 December 2019 | author = Karl Pentzlin |id=UTC L2/13-105R}} and the square had previously appeared in the BS_Viewdata character set, as a replacement for the underscore.{{cite iso-ir |title=Alphanumerics for viewdata and broadcast teletext |sponsor=BSI |sponsor-link=BSI Group |date=1981-06-01 |number=47}}

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. {{as of|2019}} (Unicode 12.1), these changes have not been accepted/implemented.{{cite web |url=https://www.unicode.org/charts/PDF/U2300.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://www.unicode.org/charts/PDF/U2300.pdf |archive-date=2022-10-09 |url-status=live |title=Miscellaneous Technical |work=The Unicode Standard |author=Unicode Consortium |author-link=Unicode Consortium}}

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.

There are a number of factors still holding up a move to a Web-based standard. Viewdata is regarded within the industry as low-cost and reliable, travel consultants have been trained to use Viewdata and would need training to book holidays on the Internet, and tour operators cannot agree on a Web-based standard.

{{Citation needed|date=December 2009}}

{{Unreferenced section|date=June 2023}}

It was made in the late 1970s and early 1980s to make it easier for travel consultants to check availability and make bookings for holidays.

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.

• Prestel

{{refs}}

• [http://www.its.bldrdoc.gov/fs-1037/dir-039/_5795.htm Definition at The Institute for Telecommunication Sciences]
• [http://www.viewdata.org.uk/ Celebrating the Viewdata Revolution] Including several Prestel Brochures
• [https://vd-view.azurewebsites.net/ vd-view] A Viewtex web client for TeeFax, Telstar, CCl4 and NXTel
• [https://github.com/simonlaszcz/vidtex vidtex] An ncurses/terminal client for TeeFax, Telstar, CCl4, NXTel and others
• {{FS1037C}}

{{Videotex}}

Category:Computer network technology

Category:History of computing in the United Kingdom

Category:History of telecommunications in the United Kingdom

Category:Legacy systems

Category:Videotex