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 CPUs, RAM modules and hard disk drives are powered down, although some internal components, such as an internal clock, may retain power.
The shutdown feature and command is available in Microsoft Windows, [1] ReactOS, [2] HP MPE/iX, [3] and in a number of Unix and Unix-like operating systems such as Apple macOS.
In Microsoft Windows and ReactOS, a PC or server is shut down by selecting the Shutdown item from the Start menu 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), 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. [4]
 The shutdown command on Windows 10 | |
| Developer(s) | Microsoft, ReactOS Contributors |
|---|---|
| Operating system | Windows, ReactOS |
| Type | Command |
| License | Windows: Proprietary commercial software ReactOS: GNU General Public License |
| Website | docs |
There is also a shutdown command that can be executed within a command shell window. shutdown.exe is the command-line shutdown application (located in %windir%\System32\shutdown.exe) [5] 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. [6]
| Parameter | Function |
|---|---|
| -l | Logs off a user. This is the default even without using any parameters. |
| -a | Stops shutdown.exe. It is used during a time-out period. |
| -f | Kills all running applications. |
| -s | Turns off the computer. |
| -r | Shuts down and reboots a computer. |
| -m[\\ Computer Name] | When shutting down a network computer, allows user to choose which computer to turn off. |
| -t xx | Timer before shut down occurs. By default it is set to 30 seconds. |
| -c "message" | Allows a message to be shown in the System Shutdown window. It can not be more than 127 characters. |
In Apple macOS the computer can be shut down by choosing "Shut Down…" from the Apple Menu, by pressing Control+Power key/button (or Media Eject 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 as well. [7] It can also be shut down by pressing Control+⌥ Option+⌘ Command+Power key/button (or Media Eject key) or clicking Shut Down on the Apple Menu while holding the ⌥ Option key, but this will not prompt the user anything at all. [8] On newer and some older Apple computers, starting with Mac OS 9, 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.
| Original author(s) | Scott James Remnant |
|---|---|
| Developer(s) | Canonical |
| Operating system | Unix-like |
| Type | Command |
In Unix and Linux, the shutdown command can be used to turn off or reboot a computer. Only the superuser or a user with special privileges 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. [9]
The cd command, also known as chdir, is a command-line shell command used to change the current working directory in various operating systems. It can be used in shell scripts and batch files.
In computing, a Control keyCtrl is a modifier key which, when pressed in conjunction with another key, performs a special operation. Similarly to the Shift key, the Control key rarely performs any function when pressed by itself. The Control key is located on or near the bottom left side of most keyboards, with many featuring an additional one at the bottom right.
In computing, at is a command in Unix-like operating systems, Microsoft Windows, and ReactOS used to schedule commands to be executed once, at a particular time in the future.
A kernel panic is a safety measure taken by an operating system's kernel upon detecting an internal fatal error in which either it is unable to safely recover or continuing to run the system would have a higher risk of major data loss. The term is largely specific to Unix and Unix-like systems. The equivalent on Microsoft Windows operating systems is a stop error, often called a "blue screen of death".
ipconfig is a console application program of some computer operating systems that displays all current TCP/IP network configuration values and refreshes Dynamic Host Configuration Protocol (DHCP) and Domain Name System (DNS) settings. IPCONFIG
The Alt keyAlt on a computer keyboard is used to change (alternate) the function of other pressed keys. Thus, the Alt key is a modifier key, used in a similar fashion to the Shift key. For example, simply pressing A will type the letter 'a', but holding down the Alt key while pressing A will cause the computer to perform an Alt+A function, which varies from program to program. The international standard ISO/IEC 9995-2 calls it Alternate key. The key is located on either side of the space bar, but in non-US PC keyboard layouts, rather than a second Alt key, there is an 'Alt Gr' key to the right of the space bar. Both placements are in accordance with ISO/IEC 9995-2. With some keyboard mappings, the right Alt key can be reconfigured to function as an AltGr key although not engraved as such.
In computing, echo is a command that outputs the strings that are passed to it as arguments. It is a command available in various operating system shells and typically used in shell scripts and batch files to output status text to the screen or a computer file, or as a source part of a pipeline.
Common User Access (CUA) is a standard for user interfaces to operating systems and computer programs. It was developed by IBM and first published in 1987 as part of their Systems Application Architecture. Used originally in the MVS/ESA, VM/CMS, OS/400, OS/2 and Microsoft Windows operating systems, parts of the CUA standard are now implemented in programs for other operating systems, including variants of Unix. It is also used by Java AWT and Swing.
In computing, kill is a command that is used in several popular operating systems to send signals to running processes.
The Option key, ⌥, is a modifier key present on Apple keyboards. It is located between the Control key and the Command key on a typical Mac keyboard. There are two Option keys on modern Mac desktop and notebook keyboards, one on each side of the space bar.
Safe mode is a diagnostic mode of a computer operating system (OS). It can also refer to a mode of operation by application software. Safe mode is intended to help fix most, if not all, problems within an operating system. It is also widely used for removing rogue security software.
A menu bar is a graphical control element which contains drop-down menus.
yes is a command on Unix and Unix-like operating systems, which outputs an affirmative response, or a user-defined string of text, continuously until killed.
Hibernation in computing is powering down a computer while retaining its state. When hibernation begins, the computer saves the contents of its random access memory (RAM) to a hard disk or other non-volatile storage. When the computer is turned on the RAM is restored and the computer is exactly as it was before entering hibernation. Hibernation was first implemented in 1992 and patented by Compaq Computer Corporation in Houston, Texas.
The clipboard is a buffer that some operating systems provide for short-term storage and transfer within and between application programs. The clipboard is usually temporary and unnamed, and its contents reside in the computer's RAM.
Single-user mode is a mode in which a multiuser computer operating system boots into a single superuser. It is mainly used for maintenance of multi-user environments such as network servers. Some tasks may require exclusive access to shared resources, for example running fsck on a network share. This mode can also be used for security purposes – network services are not run, eliminating the possibility of outside interference. On some systems a lost superuser password can be changed by switching to single-user mode, but not asking for the password in such circumstances is viewed as a security vulnerability.
In computing, ren is a command in various command-line interpreters (shells) such as COMMAND.COM, cmd.exe, 4DOS, 4NT and Windows PowerShell. It is used to rename computer files and in some implementations also directories. It is analogous to the Unix mv command. However, unlike mv, ren cannot be used to move files, as a new directory for the destination file may not be used. Alternatively, move may be used if available. On versions of MS-DOS that do not support the move command, the user would simply copy the file to a new destination, and then delete the original file. A notable exception to this rule is DOSBox, in which ren may be used to move a file, since move is not supported.
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 in which the power to the system is physically turned off and back on again ; or a warm reboot in which the system restarts while still powered up. The term restart is used to refer to a reboot when the operating system closes all programs and finalizes all pending input and output operations before initiating a soft reboot.
Control-Alt-Delete is a computer keyboard command on IBM PC compatible computers, invoked by pressing the Delete key while holding the Control and Alt keys: Ctrl+Alt+Delete. The function of the key combination differs depending on the context but it generally interrupts or facilitates interrupting a function. For instance, in pre-boot environment or in MS-DOS, Windows 3.0 and earlier versions of Windows or OS/2, the key combination reboots the computer. Starting with Windows 95, the key combination invokes a task manager or security related component that facilitates ending a Windows session or killing a frozen application.
The power key, or power button, is a key found on many computer keyboards during the 1980s and into the early 2000s. They were introduced on the first Apple Desktop Bus keyboards in the 1980s and have been a standard feature of many Macintosh keyboards since then. They are also found on an increasing number of Microsoft Windows keyboards, sometimes supplanted with additional keys for sleep. The power key is becoming increasingly rare.
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