Editing Computer terminal (section)

== System console ==
[[File:KNOPPIX_booting.png|thumb|300x300px|Knoppix system console showing the boot process]]
One meaning of '''system console''', '''computer console''', '''root console''', '''operator's console''', or simply '''console''' is the text entry and display device for system administration messages, particularly those from the [[BIOS]] or [[boot loader]], the [[Kernel (operating system)|kernel]], from the [[init]] system and from the [[Syslog|system logger]]. It is a physical device consisting of a keyboard and a printer or screen, and traditionally is a [[text terminal]], but may also be a [[graphical terminal]].

Another, older, meaning of system console, computer console, '''hardware console''', operator's console or simply console is a hardware component used by an [[Computer operator|operator]] to control the hardware, typically some combination of [[front panel]], keyboard/printer and keyboard/display.

=== History ===
[[File:IBM_1620_Model_1.jpg|thumb|[[IBM 1620]] console, with a typewriter and front panel]]
Prior to the development of alphanumeric [[Cathode-ray tube|CRT]] system consoles, some computers such as the [[IBM 1620]] had console typewriters and [[Front panel|front panels]] while the very first electronic [[stored-program computer]], the [[Manchester Baby]], used a combination of electromechanical switches and a CRT to provide console functions—the CRT displaying memory contents in binary by mirroring the machine's [[Williams tube|Williams-Kilburn tube]] CRT-based RAM.

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 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]].

Some PC [[BIOS|BIOSes]], especially in servers, also support serial consoles, giving access to the BIOS through a serial port so that the simpler and cheaper serial console infrastructure can be used. Even where BIOS support is lacking, some [[Operating system|operating systems]], e.g. [[FreeBSD]] and [[Linux]], can be configured for serial console operation either during bootup, or after startup.

Starting with the [[IBM 9672]], IBM large systems have used a [[IBM Hardware Management Console|Hardware Management Console]] (HMC), consisting of a PC and a specialized application, instead of a 3270 or serial link. Other IBM product lines also use an HMC, e.g.,  [[IBM System p|System p]].

It is usually possible to [[Logging (computer security)|log in]] from the console. Depending on configuration, the operating system may treat a login session from the console as being more trustworthy than a login session from other sources.