Control-Alt-Delete (often abbreviated to Ctrl-Alt-Del, also known as the "three-finger salute")[1][2][3][4][5] is a computer keyboard command on IBM PC compatible systems that can be used to reboot the computer, and summon the task manager or Windows Security in more recent versions of the Microsoft Windows operating system. It is invoked by pressing the Delete key while holding the Control and Alt keys: <kbd class="keyboard-key" style="border: 1px solid; border-color: #ddd #bbb #bbb #ddd; border-bottom-width: 2px; -moz-border-radius: 3px; -webkit-border-radius: 3px; border-radius: 3px; background-color: #f9f9f9; padding: 1px 3px; font-family: inherit; font-size: 0.85em; white-space: nowrap;">Ctrl</kbd>+<kbd class="keyboard-key" style="border: 1px solid; border-color: #ddd #bbb #bbb #ddd; border-bottom-width: 2px; -moz-border-radius: 3px; -webkit-border-radius: 3px; border-radius: 3px; background-color: #f9f9f9; padding: 1px 3px; font-family: inherit; font-size: 0.85em; white-space: nowrap;">Alt</kbd>+<kbd class="keyboard-key" style="border: 1px solid; border-color: #ddd #bbb #bbb #ddd; border-bottom-width: 2px; -moz-border-radius: 3px; -webkit-border-radius: 3px; border-radius: 3px; background-color: #f9f9f9; padding: 1px 3px; font-family: inherit; font-size: 0.85em; white-space: nowrap;">Delete</kbd>. It forces a soft reboot, brings up the task manager (on Windows and BeOS) or a jump to ROM monitor. In most X desktops, it brings up the Logout dialog. These keys are sometimes referred to in computer manuals as interrupt keys, since they are often used to interrupt the operation of a malfunctioning program.
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This keyboard combination was invented by David Bradley, a designer of the original IBM PC. Bradley originally designed Control-Alt-Escape to trigger a soft reboot (without warning or confirmation by the user), but he found it was too easy to bump the left side of the keyboard and reboot the computer accidentally. He switched the key combination to Control-Alt-Delete, a combination that was impossible to press with just one hand (this is not true of later keyboards, such as the 102-key PC/AT keyboard or the Maltron keyboard).[6] More advanced operating systems use its status as a "reserved" combination for various purposes, but often retain the ability to trigger a soft reboot in certain configurations or circumstances. Bradley is also known for his good-natured jab at Bill Gates, at that time the CEO of Microsoft, and also the creator of many of Microsoft's programs: "I may have invented Control-Alt-Delete, but Bill Gates made it famous". He afterwards elaborated that it was made more famous due to Windows NT logon procedures ("Press Ctrl + Alt + Delete to log on"). However, while Bradley implemented the key sequence in the ROM BIOS, he did not suggest it; the team of the then chief programmer of the IBM PC Project, Mel Hallerman, did.[1]
Play me online?/Well you know that I'll beat you
/If I ever meet you/I'll Control-Alt-Delete you.
As computers became ubiquitous, so too, has the jargon. Control-Alt-Delete can also mean "dump," or "do away with."[7]
On a PC running DOS or a system that runs in real mode, this keystroke combination is recognized by the keyboard handling code in the BIOS unless the keyboard interrupt has been hooked by some other resident program. The BIOS reacts by invoking a soft (aka warm) reboot. Under Windows 3.0 and earlier (and Windows 3.1x running in Standard mode), Control-Alt-Delete reboots the computer as in MS-DOS.
In Windows 3.1x running in 386 Enhanced mode, Windows 95, Windows 98, and Windows Me, this keystroke combination is recognised by the Windows keyboard device driver. According to the value of the LocalReboot option in the [386Enh] section of system.ini, Windows performs one of several actions in response:
Killing tasks/processes is useful, for instance, if a program has entered an infinite loop. Theoretically, the system's other processes should continue normally—in practice, using this key combination to terminate a program/process in Windows 3.1 can result in resources and memory being leaked. As such, it is strongly recommended that, following a process kill in these versions of Windows, any work should be saved in any other applications and Windows should be restarted. Such damage is much less likely in newer versions of DOS-based Windows because of resource tracking.
In Windows 9x, pressing the combination a second time if the process listing has not appeared will display a blue screen from which the user can reboot the system by pressing the combination a third time; other times the system restarts on the second Ctrl-Alt-Delete combination. This allows the user to over-ride any "stuck" process, since no user-level program is able to define its own response to the Control-Alt-Delete key combination. However, this functionality does not always work.
In Windows NT, and thus on its successors, including Windows 2000, Windows XP, Windows Server 2003, Windows Vista, Windows Server 2008 and Windows 7, this keystroke combination is recognized (as a special system-wide "keyboard hook") by the Winlogon process, which in response instructs GINA to perform one of the following tasks:
Windows NT is designed so that, unless system security is already compromised in some other way, only the Winlogon process, a trusted system process, can receive notification of this keystroke combination. This is because the kernel remembers the process ID of the Winlogon process, and allows only that process to receive the notification. This keystroke combination is thus called the Secure Attention Sequence. A user pressing Control-Alt-Delete can be sure that it is the operating system (specifically the Winlogon process), rather than a third party program that is responding to the key combination (see Login spoofing), and that it is therefore safe to enter a password. It was chosen as the secure attention key in Windows (instead of, for example, the System Request key), because on the PC platform no program could reasonably expect to redefine this keystroke combination for its own purposes (this is the soft reboot combination in BIOS and DOS).[9]
It is also a reliable method for bringing up the Task Manager in Windows 2000 and older. All other keystroke combinations could potentially be exclusively tied up by a process that is stuck, but a user process is not able to intercept the Control-Alt-Delete sequence. Ctrl+Shift+Esc also brings up the task manager in all Windows NT versions starting with NT 4.0, even if pressing Ctrl+Alt+Del is set to bring up the Windows Security dialog. The task manager can be however disabled by Windows Group Policies.
As a side effect, users who do not have physical access to the computer's power supply and power/reset switches can be denied the ability to shut down or restart the computer, where previously (on MS-DOS and other variants of Windows) they could always use Control-Alt-Delete. However, as both the Task Manager and Windows Security have options for shutting down the computer, this operation can still be executed unless the entire system (including the Winlogon process) is unresponsive. Also, it is sometimes impossible to access and/or see the Task Manager after a full-screen application has frozen, although the Windows Security dialog, which is on a separate "secure desktop", almost always appears.
In Windows Vista and other NT operating systems based on it (such as Windows Server 2008 and Windows 7), most Ctrl+Alt+Del actions remain the same. There is no supported method of replacing the login interface (as there was in Windows XP), but there is a flexible system for modifying it. The classic logon screen has been completely removed, replaced with an updated welcome screen, similar to that from Windows XP. As in Windows XP, the welcome screen can be configured to require the user to press Ctrl+Alt+Del before logon. In Windows XP, this is done by configuring local security policy. While the default behavior is to have icons for each user, the welcome screen can be configured to prompt for a username and password, though it retains the new UI. Additionally, pressing Ctrl+Alt+Del when logged in always brings up the Windows Security screen, regardless of the logon method. Users can also lock the computer even if fast user switching is enabled.
In OS/2, this keystroke combination is recognised by the OS/2 keyboard device driver, which notifies the session manager process. The normal session manager process in OS/2 versions 2.0 and later is the parent Workplace Shell process, which displays the "The system is rebooting" window and triggers a soft reboot. If it is pressed twice in succession OS/2 triggers an immediate soft reboot, without waiting for the session manager process.
In both cases, the system flushes the page cache, cleanly unmounts all disc volumes, but does not cleanly shut down any running programs (and thus does not save any unsaved documents, or the current arrangements of the objects on the Workplace Shell desktop or in any of its open folders).
Ctrl-Alt-Delete is not specified as a keyboard shortcut for anything on the Mac and various other platforms. However, in the Mac OS X Server logon screen, pressing <kbd class="keyboard-key" style="border: 1px solid; border-color: #ddd #bbb #bbb #ddd; border-bottom-width: 2px; -moz-border-radius: 3px; -webkit-border-radius: 3px; border-radius: 3px; background-color: #f9f9f9; padding: 1px 3px; font-family: inherit; font-size: 0.85em; white-space: nowrap;">Control</kbd>-<kbd class="keyboard-key" style="border: 1px solid; border-color: #ddd #bbb #bbb #ddd; border-bottom-width: 2px; -moz-border-radius: 3px; -webkit-border-radius: 3px; border-radius: 3px; background-color: #f9f9f9; padding: 1px 3px; font-family: inherit; font-size: 0.85em; white-space: nowrap;">Option</kbd>-<kbd class="keyboard-key" style="border: 1px solid; border-color: #ddd #bbb #bbb #ddd; border-bottom-width: 2px; -moz-border-radius: 3px; -webkit-border-radius: 3px; border-radius: 3px; background-color: #f9f9f9; padding: 1px 3px; font-family: inherit; font-size: 0.85em; white-space: nowrap;">Delete</kbd> will show an alert saying "This is not DOS." [10]
Sleep Display:
Sleep:
Quit all applications and restart:
Restart, Sleep or Shut Down (dialogue):
In an emergency — or if normal actions are impossible/ineffective — as a last resort, you may force things. Be aware that forcing things to quit, restart or stop may have undesirable effects such as data loss.
For windowed processes/applications, to present the Force Quit Applications dialogue:
Activity Monitor utility can quit, or force quit, any process.
Some Macs have a <kbd class="keyboard-key" style="border: 1px solid; border-color: #ddd #bbb #bbb #ddd; border-bottom-width: 2px; -moz-border-radius: 3px; -webkit-border-radius: 3px; border-radius: 3px; background-color: #f9f9f9; padding: 1px 3px; font-family: inherit; font-size: 0.85em; white-space: nowrap;">◁ Reset</kbd> button.
On the Apple IIe, Apple IIc, and the Apple III, Control—Open-Apple—Reset would cause an immediate restart.
| Platform | Key combination | Function |
|---|---|---|
| Acorn Machines (pre-1987) | Break | Processor reset, although confusingly always referred to as soft reset. Hold down Ctrl as well for so-called hard reset (reinitializes various settings); hold down Shift to boot from disk (or not to, if disk is the default). |
| Acorn and post-Acorn RISC OS machines. | Reset button | Processor reset, although confusingly always referred to as soft reset. Hold down Ctrl as well for so-called hard reset (reinitializes various settings); hold down Shift to boot from disk (or not to, if disk is the default). Hold down various other keys to restore CMOS settings to safe configurations. |
| Ctrl + Break | Perform a soft reboot. | |
| Amiga | Ctrl + Left Amiga (or Commodore) + Right Amiga | Hard reset. The reset will be instant unless a specific hardware delay function has been activated. |
| Amstrad CPC 464 and CPC6128 | Ctrl + Shift + Esc | Reset (cold) |
| Amstrad PCW | Shift + Extra + Exit | Reset (cold) |
| Shift + Extra + Relay | Warm boot from the currently-inserted floppy disc. Is able to boot from discs in LocoScript installer format, which cannot be loaded by the normal ROM loader. | |
| Atari ST | Ctrl + Alt + Del | Soft reset. Under FreeMiNT >= 1.16 it won't be instant, disk partitions are unmounted first. Ctrl + Alt + Shift + Del will perform hard reset. |
| BlackBerry | Alt + Right shift + Delete | Soft reboot. |
| IBM PC under DOS | Ctrl + Alt + Del | Perform a soft reboot |
| IBM PC under Windows 3.x shell | Ctrl + Alt + Del | Close unresponsive applications or (if pressed twice) perform a soft reboot |
| IBM PC under Microsoft Windows (95, 98, and Me) | Ctrl + Alt + Del | Bring up simplistic task manager (actually "Close Program" dialog) or (if pressed twice) perform a soft reboot |
| IBM PC under Windows NT-based OS (NT, 2000, XP, 2003, Vista and Windows 7) | Ctrl + Shift + Esc | Bring up the Windows Task Manager |
| Ctrl + Alt + Del | Also known as the Secure Attention Sequence; bring up the logins screen (when pressed in login screen), or the "Windows security" dialog or (configurable on Windows 2000 and later) the Windows Task Manager (when logged in) | |
| IBM PC under OS/2 | Ctrl + Esc | Bring up the Window List (unblocking the synchronous input queue) |
| Ctrl + Alt + Del | Perform a soft reboot | |
| Ctrl + Alt + NumLock (twice) | Halt the system and begin a system dump to floppy disk | |
| IBM PC under Linux | Ctrl + Alt + Del | Signal the init process (usually configured to soft reboot) |
| Alt + SysRq + function key | Magic SysRq key: Depending on the function key, performs a certain low-level function. Examples: sync (flush caches), reboot (forced soft reboot), unmount (remount filesystems readonly), etc... | |
| IBM PC under other OS | Ctrl + Alt + Del | Often (but not always) configured to reboot |
| Sinclair ZX Spectrum | Break | Halted peripheral (cassette tape or printer) operations with the report D BREAK – CONT repeats, or halted BASIC programs with the report L BREAK into program. |
| Sun workstation | L1/Stop + A | Enter ROM monitor |
| Sun workstation (serial console) | Break | Enter ROM monitor |
| Alphas running OpenVMS | Ctrl + P | Enter ROM Serial Console or reboot, depending on setting in SRM |
| Apple II series machines | Ctrl + Reset | Enter the monitor or ROM BASIC |
| Ctrl + Open Apple + Reset | Reboot the machine | |
| Ctrl + Option (Closed Apple) + Reset | Enter BIOS setup, then reboot | |
| Ctrl + Option (Closed Apple) + Open Apple + Reset | Self-test, then reboot | |
| Ctrl + Open Apple + Escape | Kill application | |
| Apple Macintosh computers with power button on keyboard | Command + Power | Enter debugger |
| Control + Command + Power (sometimes known as a "Control Flower Power") | Reboot the machine | |
| Mac OS (7 and later) | Option + Command + Esc | Force quit applications |
| S60 Platform (used on some mobile phones such as Nokia smartphones) | Green (call answer) + * + 3 (while restarting the phone) | Wipes internal memory and resets the device |
| SGI workstation | Left Shift + Left Ctrl + Left Alt + Keypad Divide + F12 | Restart X server (same as Ctrl + Alt + Backspace below). Nicknamed "the death-grip" due to the contorted finger positions. |
| Commodore 64 & Vic-20 | Run/Stop + Restore | Halt (soft reconfiguration) and return to READY prompt |
| Commodore 128 | Reset | Reset to power on state in current mode |
| Commodore + Reset | Reset to C-64 mode | |
| Run/Stop + Reset | Reset to ML monitor preserving contents of BASIC memory | |
| X Window System | Ctrl + Alt + Backspace | Immediately kills the X server (the key can be disabled). When using an X Display Manager, it will usually start the X server again. |
| TI-30XIIS | On + Clear | Restarts the calculator and clears RAM |
| TI-80, TI-81, TI-82, TI-83, TI-84 | Mode, Alpha, S | Shows ROM version number. [Enter] enters self test mode |
| TI-85, TI-86 | 2nd, Mode, Alpha, S | Shows ROM version number. [Enter] enters self test mode |
| TI-89 | 2nd + Left Arrow + Right Arrow + On | Restarts the calculator and clears RAM
Esc + On Force Break without restarting RAM |
| Many Natural Display Casio Calculators | Shift + 7 + On | Restarts the calculator and clears RAM and EEPROM.
Continue pressing Shift to advance through self-test mode. |
| TI-99/4A | FCTN-+ | Resets machine back to startup screen. |
| Voyage 200 | 2nd + Hand + On | Restarts the calculator and clears RAM |
| HP-48 | On + C | Restarts RPL, clearing the Stack and PICT, closing IO, and returning to the HOME directory (but not purging the memory) |
| On + A + F | As above, but also purges the memory | |
| BeOS | Ctrl-Alt-Shift and click an applications entry in the Deskbar | Kills application |
| Zenith IBM PC clones | Ctrl-Alt-Ins | Brings up hardware configuration menu |
| Scientific Atlanta Explorer DHCT | Volume Down + Volume Up + Info (on settop box; not remote) | Reboots box (starts up to blue EXPLORER screen) |
| Olivetti M20 | Ctrl + Reset | Soft resets the machine |
| TI Explorer Lisp Machine | Left-Ctrl Left-Meta Right-Ctrl Right-Meta Abort | Restart the system |
| Xfce | Ctrl + Alt + Esc + click on window | Kill application |
| Foxtel Set-top-boxes | Back + Select (on box; not remote) (except UEC 720). Standby + Foxtel (on box; not remote) (UEC 720). Back + Select + Reset (on box; not remote) (iQ2) | Power cycles the machine. Pressing [Power], Up, Down, [Power] when lights illuminate on box forces firmware update.[13] |
| iPod nano 3rd Generation | Play/Pause + Center button (hold down until Apple logo shows) | Reboots the iPod to the Apple logo that you see when you turn the iPod on for the first time. |
| iPod nano 4th Generation | Menu + Center button (hold down until Apple logo shows) | Reboots the iPod to the Apple logo that you see when you turn the iPod on for the first time. |
| iPod Touch, iPhone, and iPad | Top Power Button + Center Home Button (hold down until Apple logo shows)[14] | Reboots the iPod, iPhone, or iPad to the Apple logo that you see when you turn the device on for the first time. |
| Android devices, particularly the Nexus One | Track ball + volume down + power, all held down until power off | reboot normally if all buttons are released; reboot into bootloader if the volume down button is continuously held |
| (from power off) volume down (held continuously) + Power button | Enter the bootloader | |
| Alt + Shift + Del (on the device's hardware keyboard, if available) | Reboots the device, particularly the Motorola Droid and its successor |
The keystrokes are well known and infamous for escaping from problems in pop culture. For example, in the Billy Talent song "Perfect World", part of the lyrics include the sequence and associate it with resetting their memory and escaping from a situation: "Control-Alt-Deleted. Reset my memory."[15] They were also used in a line in the "Weird Al" Yankovic Song - It's all about the Pentiums. "Play me online and you know that I'll beat you. If I ever meet you, I'll Control, alt, delete you" [16]
LocalReboot in Windows 95LocalReboot between Windows 3.x and Windows 95| Esc | F1 | F2 | F3 | F4 | F5 | F6 | F7 | F8 | F9 | F10 | F11 | F12 | PrtScn/ SysRq |
ScrLk | Pause/ Break |
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