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To shut down or power off a computer is to remove power from a computer's main components in a controlled way. After a computer is shut down, main components such as
CPU A central processing unit (CPU), also called a central processor, main processor or just processor, is the electronic circuitry that executes instructions comprising a computer program. The CPU performs basic arithmetic, logic, controlling, and ...
s,
RAM Ram, ram, or RAM may refer to: Animals * A male sheep * Ram cichlid, a freshwater tropical fish People * Ram (given name) * Ram (surname) * Ram (director) (Ramsubramaniam), an Indian Tamil film director * RAM (musician) (born 1974), Dutch * Raj ...
modules and
hard disk drive A hard disk drive (HDD), hard disk, hard drive, or fixed disk is an electro-mechanical data storage device that stores and retrieves digital data using magnetic storage with one or more rigid rapidly rotating platters coated with magneti ...
s are powered down, although some internal components, such as an internal clock, may retain power.


Implementations

The shutdown feature and
command Command may refer to: Computing * Command (computing), a statement in a computer language * COMMAND.COM, the default operating system shell and command-line interpreter for DOS * Command key, a modifier key on Apple Macintosh computer keyboards * ...
is available in
Microsoft Microsoft Corporation is an American multinational technology corporation producing computer software, consumer electronics, personal computers, and related services headquartered at the Microsoft Redmond campus located in Redmond, Washingt ...
Windows Windows is a group of several Proprietary software, proprietary graphical user interface, graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, W ...
,
ReactOS ReactOS is a free and open-source operating system for amd64/ i686 personal computers intended to be binary-compatible with computer programs and device drivers made for Windows Server 2003 and later versions of Windows. ReactOS has been noted ...
, HP MPE/iX, and in a number of
Unix Unix (; trademarked as UNIX) is a family of multitasking, multiuser computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, and ot ...
and Unix-like operating systems such as Apple
macOS macOS (; previously OS X and originally Mac OS X) is a Unix operating system developed and marketed by Apple Inc. since 2001. It is the primary operating system for Apple's Mac computers. Within the market of desktop and lap ...
.


Microsoft Windows and ReactOS

In
Microsoft Windows Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for se ...
and
ReactOS ReactOS is a free and open-source operating system for amd64/ i686 personal computers intended to be binary-compatible with computer programs and device drivers made for Windows Server 2003 and later versions of Windows. ReactOS has been noted ...
, a PC or server is shut down by selecting the item from the
Start menu The Start menu is a graphical user interface element used in Microsoft Windows since Windows 95 and in other operating systems. It provides a central launching point for computer programs and performing other tasks in the Windows shell. It is name ...
on the desktop. Options include shutting down the system and powering off, automatically restarting the system after shutting down, or putting the system into stand-by mode. Just like other operating systems, Windows has the option to prohibit selected users from shutting down a computer. On a home PC, every user may have the shutdown option, but in computers on large networks (such as
Active Directory Active Directory (AD) is a directory service developed by Microsoft for Windows domain networks. It is included in most Windows Server operating systems as a set of processes and services. Initially, Active Directory was used only for centrali ...
), an administrator can revoke the access rights of selected users to shut down a Windows computer. Nowadays there are many software utilities which can automate the task of shutting down a Windows computer, enabling automatic computer control. The Windows Shutdown website lists various software utilities to automate the task of shutting down. In Windows, a program can shut down the system by calling the ExitWindowsEx or NtShutdownSystem function.


Command-line interface

There is also a shutdown
command Command may refer to: Computing * Command (computing), a statement in a computer language * COMMAND.COM, the default operating system shell and command-line interpreter for DOS * Command key, a modifier key on Apple Macintosh computer keyboards * ...
that can be executed within a
command shell In computing, a shell is a computer program that exposes an operating system's services to a human user or other programs. In general, operating system shells use either a command-line interface (CLI) or graphical user interface (GUI), dependin ...
window. shutdown.exe is the
command-line A command-line interpreter or command-line processor uses a command-line interface (CLI) to receive commands from a user in the form of lines of text. This provides a means of setting parameters for the environment, invoking executables and pro ...
shutdown application (located in %windir%\System32\shutdown.exe) that can shut down the user's computer or another computer on the user's network. Different parameters allow different functions. More than one parameter can be used at a time for this command.


Apple macOS

In Apple
macOS macOS (; previously OS X and originally Mac OS X) is a Unix operating system developed and marketed by Apple Inc. since 2001. It is the primary operating system for Apple's Mac computers. Within the market of desktop and lap ...
the computer can be shut down by choosing "Shut Down…" from the
Apple Menu The Apple menu is a drop-down Menu (computing), menu that is on the left side of the menu bar in the classic Mac OS, macOS and A/UX operating systems. The Apple menu's role has changed throughout the history of Apple Inc.'s operating systems, b ...
, by pressing key/button (or key), or by pressing the power key to bring up the power management dialog box and selecting button "Shut down". An administrator may also use the Unix shutdown
command Command may refer to: Computing * Command (computing), a statement in a computer language * COMMAND.COM, the default operating system shell and command-line interpreter for DOS * Command key, a modifier key on Apple Macintosh computer keyboards * ...
as well. It can also be shut down by pressing key/button (or key) or clicking Shut Down on the Apple Menu while holding the key, but this will not prompt the user anything at all. On newer and some older Apple computers, starting with
Mac OS 9 Mac OS 9 is the ninth major release of Apple's classic Mac OS operating system which was succeeded by Mac OS X (renamed to OS X in 2011 and macOS in 2016) in 2001. Introduced on October 23, 1999, it was promoted by Apple as "The Best Internet O ...
, the user is given a time limit in which the computer will automatically shut down if the user does not click the "Shut Down" button.


Unix and Linux

In
Unix Unix (; trademarked as UNIX) is a family of multitasking, multiuser computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, and ot ...
and
Linux Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, which in ...
, the shutdown command can be used to turn off or
reboot In computing, rebooting is the process by which a running computer system is restarted, either intentionally or unintentionally. Reboots can be either a cold reboot (alternatively known as a hard reboot) in which the power to the system is phy ...
a computer. Only the
superuser In computing, the superuser is a special user account used for system administration. Depending on the operating system (OS), the actual name of this account might be root, administrator, admin or supervisor. In some cases, the actual name of th ...
can shut the system down. One commonly issued form of this command is shutdown -h now, which will shut down a system immediately. Another one is shutdown -r now to reboot. Another form allows the user to specify an exact time or a delay before shutdown: shutdown -h 20:00 will turn the computer off at 8:00 PM, and shutdown -r +1 will automatically reboot the machine in one minute of issuing the command.


See also

*
Booting In computing, booting is the process of starting a computer as initiated via hardware such as a button or by a software command. After it is switched on, a computer's central processing unit (CPU) has no software in its main memory, so some ...
*
Hibernation Hibernation is a state of minimal activity and metabolic depression undergone by some animal species. Hibernation is a seasonal heterothermy characterized by low body-temperature, slow breathing and heart-rate, and low metabolic rate. It most ...
*
Sleep mode Sleep mode (or suspend to RAM) is a low power mode for electronic devices such as computers, televisions, and remote controlled devices. These modes save significantly on electrical consumption compared to leaving a device fully on and, upon resu ...
*
Ctrl+Alt+Del Control-Alt-Delete (often abbreviated to Ctrl+Alt+Del, also known as the "three-finger salute" or "Security Keys") is a computer keyboard command on IBM PC compatible computers, invoked by pressing the Delete key while holding the Control and ...


References


Further reading

* * * *


External links


shutdown , Microsoft Docsshutdown.cc
– an article about various ways of automated and manual shutting down of Microsoft Windows {{DEFAULTSORT:Shutdown (Computing) Operating system technology Windows commands Windows administration MacOS Unix process- and task-management-related software