Computer terminal: Difference between revisions

Revision as of 02:00, 4 September 2024

Revision as of 02:00, 4 September 2024

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Some early operating systems supported either a single keyboard/print or keyboard/display device for controlling the OS. Some also supported a single alternate console, and some supported a [[Hard copy|hardcopy]] console for retaining a record of commands, responses and other console messages. However, in the late 1960s it became common for operating systems to support many more consoles than 3, and operating systems began appearing in which the console was simply any terminal with a privileged user logged on.

On early [[Minicomputer|minicomputers]], the console was a '''serial console''', an [[RS-232]] serial link to a [[Computer terminal|terminal]] such as a [[Teletype Model 33|ASR-33]] or, later, a terminal from [[Digital Equipment Corporation]] (DEC), e.g., [[DECwriter|DECWriter]], [[VT100]]. This terminal was usually kept in a secured room since it could be used for certain privileged functions such as halting the system or selecting which media to boot from. Large [[Midrange computer|midrange systems]], e.g. those from [[Sun Microsystems]], [[Hewlett-Packard]] and [[IBM]],{{cn|reason=I know of no current IBM midrange system that still uses a serial console.|date=January 2022}} still use serial consoles. In larger installations, the console ports are attached to multiplexers or network-connected multiport serial servers that let an operator connect a terminal to any of the attached servers. Today, serial consoles are often used for accessing [[Headless computer|headless systems]], usually with a [[terminal emulator]] running on a [[laptop]]. Also, routers, enterprise [[Network switch|network switches]] and other telecommunication equipment have RS-232 serial console ports.

On [[Personal computer|PCs]] and [[Workstation|workstations]], the computer's attached [[Computer keyboard|keyboard]] and [[Computer monitor|monitor]] have the equivalent function. Since the monitor cable carries video signals, it cannot be extended very far. Often, installations with many servers therefore use keyboard/video multiplexers ([[KVM switch|KVM switches]]) and possibly video amplifiers to centralize console access. In recent years, [[KVM/IP]] devices have become available that allow a remote computer to view the video output and send keyboard input via any TCP/IP network and therefore the [[Internet]].