Virtual Terminal

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Virtual Terminal ( VT ) is the name of an OSI protocol and service. This is a general device interface that enables the representation of data structures on different device classes. It allows a computer application to control a wide variety of terminals, keyboards and printers. It includes the control of cursors, colors, fonts, access rights, etc. It was defined so that a large number of classic character-oriented terminals can be displayed. The main idea was that a host computer in a heterogeneous computer network does not need to know how to control any type of terminal, but only how to control a "virtual terminal". The local implementation in the respective terminal type should use the elements of the OSI protocol in order to use them to control its hardware. The simplest terminal protocol that could be emulated with this OSI protocol was the Telnet protocol.

The virtual terminal protocol has not been able to establish itself on the market, although there are a number of implementations, preferably for Unix derivatives. They were rarely implemented in terminals. The reason for this is that proprietary protocols for connecting terminals to hosts ensure that the manufacturer of the host also generates revenue from the terminals.

Norms and standards

  • ISO / IEC 9040: 1997 Information technology - Open Systems Interconnection - Virtual Terminal Basic Class Service
  • ISO / IEC 9041-1: 1997 Information technology - Open Systems Interconnection - Virtual Terminal Basic Class Protocol - Part 1: Specification