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 was credited as inventor of the system. Fedida had the idea for Viewdata in 1968. 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.
Originally Viewdata was accessed with a special purpose terminal (or emulation software) and a modem running at CCITT V.23 speed (1200 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.
As of 2015, Viewdata is 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, they would need training to book holidays on the Internet, and tour operators cannot agree on a Web-based standard.
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 Microcomputer, 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.