Control-Alt-Delete
Encyclopedia
IBM PC compatible
IBM PC compatible computers are those generally similar to the original IBM PC, XT, and AT. Such computers used to be referred to as PC clones, or IBM clones since they almost exactly duplicated all the significant features of the PC architecture, facilitated by various manufacturers' ability to...
systems that can be used to reboot the computer, and summon the task manager
Windows Task Manager
Windows Task Manager is a task manager application included with the Microsoft Windows NT family of operating systems that provides detailed information about computer performance and running applications, processes and CPU usage, commit charge and memory information, network activity and...
or Windows Security in more recent versions of the Microsoft
Microsoft
Microsoft Corporation is an American public multinational corporation headquartered in Redmond, Washington, USA that develops, manufactures, licenses, and supports a wide range of products and services predominantly related to computing through its various product divisions...
Windows
Microsoft Windows
Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
operating system. It is invoked by pressing the Delete key
Delete key
The delete key , known less ambiguously as forward delete, performs a function when struck on a computer keyboard during text or command editing, which is to discard the character ahead of the cursor's position, moving all following characters one position "back" towards the freed letterspace. The...
while holding the Control
Control key
In computing, a Control key is a modifier key which, when pressed in conjunction with another key, will perform a special operation ; similar to the Shift key, the Control key rarely performs any function when pressed by itself...
and Alt
Alt key
The Alt key on a computer keyboard is used to change 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 if you hold down either Alt key while pressing A, the computer...
keys: . It forces a soft reboot, brings up the task manager (on Windows
Microsoft Windows
Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
and BeOS
BeOS
BeOS is an operating system for personal computers which began development by Be Inc. in 1991. It was first written to run on BeBox hardware. BeOS was optimized for digital media work and was written to take advantage of modern hardware facilities such as symmetric multiprocessing by utilizing...
) or a jump to ROM monitor. In most X
X Window System
The X window system is a computer software system and network protocol that provides a basis for graphical user interfaces and rich input device capability for networked computers...
desktops
Desktop environment
In graphical computing, a desktop environment commonly refers to a style of graphical user interface derived from the desktop metaphor that is seen on most modern personal computers. These GUIs help the user in easily accessing, configuring, and modifying many important and frequently accessed...
, 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.
History
This keyboard combination was invented by David BradleyDavid Bradley (engineer)
David Bradley was one of the twelve engineers who worked on the original IBM PC, developing the computer ROM BIOScode. He is credited by some for inventing the "Control-Alt-Delete" key combination that was used to reboot the computer.-Control-Alt-Delete:...
, a designer of the original IBM PC. Bradley originally designed Control-Alt-Escape
Esc key
On computer keyboards, the Esc key is a key labeled Esc or Escape that is used to generate the ASCII Escape character , the character code traditionally used to initiate an escape sequence...
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
Maltron keyboard
PCD Maltron Ltd., d.b.a. Maltron, is a manufacturer of ergonomic special-needs keyboards, founded by South African-born inventor Lilian Malt, the namesake of the company, and manufacturer Stephen Hobday...
). More advanced operating system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
s 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
Bill Gates
William Henry "Bill" Gates III is an American business magnate, investor, philanthropist, and author. Gates is the former CEO and current chairman of Microsoft, the software company he founded with Paul Allen...
, at that time the CEO of Microsoft
Microsoft
Microsoft Corporation is an American public multinational corporation headquartered in Redmond, Washington, USA that develops, manufactures, licenses, and supports a wide range of products and services predominantly related to computing through its various product divisions...
, and also the creator of many of Microsoft's programs: "I may have invented Control-Alt-Delete, but Bill Gates
Bill Gates
William Henry "Bill" Gates III is an American business magnate, investor, philanthropist, and author. Gates is the former CEO and current chairman of Microsoft, the software company he founded with Paul Allen...
made it famous". He afterwards elaborated that it was made more famous due to Windows NT
Windows NT
Windows NT is a family of operating systems produced by Microsoft, the first version of which was released in July 1993. It was a powerful high-level-language-based, processor-independent, multiprocessing, multiuser operating system with features comparable to Unix. It was intended to complement...
logon procedures ("Press Ctrl + Alt + Delete to log on"). However, while Bradley implemented the key sequence in the ROM
Read-only memory
Read-only memory is a class of storage medium used in computers and other electronic devices. Data stored in ROM cannot be modified, or can be modified only slowly or with difficulty, so it is mainly used to distribute firmware .In its strictest sense, ROM refers only...
BIOS
BIOS
In IBM PC compatible computers, the basic input/output system , also known as the System BIOS or ROM BIOS , is a de facto standard defining a firmware interface....
, he did not suggest it; the team of the then chief programmer of the IBM PC Project, Mel Hallerman, did.
As computers became ubiquitous, so too, has the jargon
Jargon
Jargon is terminology which is especially defined in relationship to a specific activity, profession, group, or event. The philosophe Condillac observed in 1782 that "Every science requires a special language because every science has its own ideas." As a rationalist member of the Enlightenment he...
. Control-Alt-Delete can also mean "dump," or "do away with."
MS-DOS and other real mode systems
On a PCPersonal computer
A personal computer is any general-purpose computer whose size, capabilities, and original sales price make it useful for individuals, and which is intended to be operated directly by an end-user with no intervening computer operator...
running DOS
DOS
DOS, short for "Disk Operating System", is an acronym for several closely related operating systems that dominated the IBM PC compatible market between 1981 and 1995, or until about 2000 if one includes the partially DOS-based Microsoft Windows versions 95, 98, and Millennium Edition.Related...
or a system that runs in real mode
Real mode
Real mode, also called real address mode, is an operating mode of 80286 and later x86-compatible CPUs. Real mode is characterized by a 20 bit segmented memory address space and unlimited direct software access to all memory, I/O addresses and peripheral hardware...
, 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
Windows 3.0
Windows 3.0, a graphical environment, is the third major release of Microsoft Windows, and was released on 22 May 1990. It became the first widely successful version of Windows and a rival to Apple Macintosh and the Commodore Amiga on the GUI front...
and earlier (and Windows 3.1x
Windows 3.1x
Windows 3.1x is a series of 16-bit operating systems produced by Microsoft for use on personal computers. The series began with Windows 3.1, which was first sold during March 1992 as a successor to Windows 3.0...
running in Standard mode), Control-Alt-Delete reboots the computer as in MS-DOS.
DOS-based Windows
Windows 95
Windows 95 is a consumer-oriented graphical user interface-based operating system. It was released on August 24, 1995 by Microsoft, and was a significant progression from the company's previous Windows products...
, Windows 98
Windows 98
Windows 98 is a graphical operating system by Microsoft. It is the second major release in the Windows 9x line of operating systems. It was released to manufacturing on 15 May 1998 and to retail on 25 June 1998. Windows 98 is the successor to Windows 95. Like its predecessor, it is a hybrid...
, and Windows Me
Windows Me
Windows Millennium Edition, or Windows Me , is a graphical operating system released on September 14, 2000 by Microsoft, and was the last operating system released in the Windows 9x series. Support for Windows Me ended on July 11, 2006....
, 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:
- If LocalReboot=Off it performs a soft reboot.
- If LocalReboot=On:
- Windows 3.1x presents a blue screenBlue Screen of DeathTo forse a BSOD Open regedit.exe,Then search: HKLM\SYSTEM\CurrentControlSet\services\i8042prt\ParametersThen make a new DWORD called "CrashOnCtrlScroll" And set the value to 1....
to the user inviting them to press EnterEnter keyIn computer keyboards, the enter key in most cases causes a command line, window form, or dialog box to operate its default function...
to end a task that has stopped responding to the system (if such a task exists) or press Control-Alt-Delete again to perform a soft reboot. - Windows 95, Windows 98, and Windows Me, temporarily halts the entire system, and presents a window which lists currently running processesProcess (computing)In computing, a process is an instance of a computer program that is being executed. It contains the program code and its current activity. Depending on the operating system , a process may be made up of multiple threads of execution that execute instructions concurrently.A computer program is a...
, and can be used to notify them that they should end, or, when they don't respond, kill them. The user can press Control-Alt-Delete again to perform a soft reboot.
- Windows 3.1x presents a blue screen
Killing tasks/processes is useful, for instance, if a program has entered an infinite loop
Infinite loop
An infinite loop is a sequence of instructions in a computer program which loops endlessly, either due to the loop having no terminating condition, having one that can never be met, or one that causes the loop to start over...
. 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.
Windows NT (and later versions)
Windows NT
Windows NT is a family of operating systems produced by Microsoft, the first version of which was released in July 1993. It was a powerful high-level-language-based, processor-independent, multiprocessing, multiuser operating system with features comparable to Unix. It was intended to complement...
, and thus on its successors, including Windows 2000
Windows 2000
Windows 2000 is a line of operating systems produced by Microsoft for use on personal computers, business desktops, laptops, and servers. Windows 2000 was released to manufacturing on 15 December 1999 and launched to retail on 17 February 2000. It is the successor to Windows NT 4.0, and is the...
, Windows XP
Windows XP
Windows XP is an operating system produced by Microsoft for use on personal computers, including home and business desktops, laptops and media centers. First released to computer manufacturers on August 24, 2001, it is the second most popular version of Windows, based on installed user base...
, Windows Server 2003
Windows Server 2003
Windows Server 2003 is a server operating system produced by Microsoft, introduced on 24 April 2003. An updated version, Windows Server 2003 R2, was released to manufacturing on 6 December 2005...
, Windows Vista
Windows Vista
Windows Vista is an operating system released in several variations developed by Microsoft for use on personal computers, including home and business desktops, laptops, tablet PCs, and media center PCs...
, Windows Server 2008 and Windows 7, this keystroke combination is recognized (as a special system-wide "keyboard hook") by the Winlogon
Winlogon
In computing, Winlogon is the component of Microsoft Windows operating systems that is responsible for handling the secure attention sequence, loading the user profile on logon, and optionally locking the computer when a screensaver is running...
process, which in response instructs GINA
Graphical identification and authentication
The graphical identification and authentication library is a component of some Microsoft Windows operating systems that provides secure authentication and interactive logon services....
to perform one of the following tasks:
- If nobody is logged in, bringing up the login dialog to allow the user to log in. Also used when the computer is locked to bring up the unlock dialog.
- If the computer is configured as a part of a domainWindows Server domainA Windows domain is a collection of security principals that share a central directory database. This central database contains the user accounts and security information for...
or it runs Windows 2000, the combination brings up the "Windows Security" dialog, where the user can lock the computer, change their password, log out, shut the computer down, or invoke the Task Manager. This is the default behavior in Windows Vista and Windows Server 2008, regardless of whether or not the computer is part of a domain. The options presented can be controlled through the use of Group PolicyGroup PolicyGroup Policy is a feature of the Microsoft Windows NT family of operating systems. Group Policy is a set of rules that control the working environment of user accounts and computer accounts. Group Policy provides the centralized management and configuration of operating systems, applications, and...
. - If Windows XPWindows XPWindows XP is an operating system produced by Microsoft for use on personal computers, including home and business desktops, laptops and media centers. First released to computer manufacturers on August 24, 2001, it is the second most popular version of Windows, based on installed user base...
is not connected to a domain- and the Welcome Screen and fast user switchingFast user switchingFast user switching is a feature on some modern multi-user operating systems such as Windows XP and newer, Mac OS X, Linux. It allows users to switch between user accounts on a single PC without quitting applications and logging out. Analogous functionality was first developed on consumer level...
are turned on, Ctrl-Alt-Del directly invokes the Task ManagerTask managerA task manager is a program used to provide information about the processes and programs running on a computer, as well as the general status of the computer. It can also be used to terminate processes and programs, as well as change the processes priority...
. - and the Welcome Screen and fast user switchingFast user switchingFast user switching is a feature on some modern multi-user operating systems such as Windows XP and newer, Mac OS X, Linux. It allows users to switch between user accounts on a single PC without quitting applications and logging out. Analogous functionality was first developed on consumer level...
are turned off, Ctrl-Alt-Del will open the Windows Security Dialog, as described above. - If pressed twice while at the Welcome Screen the classic Windows login box is displayed. This allows one to log in as any user, even those typically hidden from the Welcome Screen.
- and the Welcome Screen and fast user switching
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
Kernel (computing)
In computing, the kernel is the main component of most computer operating systems; it is a bridge between applications and the actual data processing done at the hardware level. The kernel's responsibilities include managing the system's resources...
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
Secure attention key
A secure attention key is a special key or key combination to be pressed on a computer keyboard before a login screen must be trusted by a user. The operating system kernel, which interacts directly with the hardware, is able to detect whether the secure attention key has been pressed...
. 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
Login spoofing
Login spoofings are techniques used to steal a user's password. The user is presented with an ordinary looking login prompt for username and password, which is actually a malicious program, usually called a Trojan horse under the control of the attacker...
), 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).
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
Power supply unit (computer)
A power supply unit converts mains AC to low-voltage regulated DC power for the internal components of the computer. Modern personal computers universally use a switched-mode 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.
Windows Vista and later
OS/2
In OS/2OS/2
OS/2 is a computer operating system, initially created by Microsoft and IBM, then later developed by IBM exclusively. The name stands for "Operating System/2," because it was introduced as part of the same generation change release as IBM's "Personal System/2 " line of second-generation personal...
, 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
Page cache
In computing, page cache, sometimes ambiguously called disk cache, is a "transparent" buffer of disk-backed pages kept in main memory by the operating system for quicker access. Page cache is typically implemented in kernels with the paging memory management, and is completely transparent to...
, cleanly unmount
Mount (computing)
Mounting takes place before a computer can use any kind of storage device . The user or their operating system must make it accessible through the computer's file system. A user can access only files on mounted media.- Mount point :A mount point is a physical location in the partition used as a...
s 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).
Linux
In LinuxLinux
Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...
, this keystroke combination is recognized by the keyboard device driver in the kernel
Kernel (computing)
In computing, the kernel is the main component of most computer operating systems; it is a bridge between applications and the actual data processing done at the hardware level. The kernel's responsibilities include managing the system's resources...
. In the absence of more specific instructions, which will usually only be during system initialization, the kernel directly initiates a soft reboot in response. More commonly, the kernel will send a signal to the init process, which will perform an administrator-configured task, such as running a script, or displaying an "end current session" box in KDE
KDE
KDE is an international free software community producing an integrated set of cross-platform applications designed to run on Linux, FreeBSD, Microsoft Windows, Solaris and Mac OS X systems...
.
In many Linux distributions, init is configured to switch run levels and to perform a soft reboot in response to the signal. Thus it provides a mechanism for a person with physical access to the keyboard to perform system shut down (a task that requires superuser
Superuser
On many computer operating systems, the superuser is a special user account used for system administration. Depending on the operating system, the actual name of this account might be: root, administrator or supervisor....
rights to initiate programmatically). However, Linux systems can be configured to ignore the keystroke combination. The setting is usually in the inittab(5) configuration file under the keyword "ca".
Linux also has a similar sequence of keystrokes for restarting the computer described at the article Magic SysRq key.
Under the X Window System
X Window System
The X window system is a computer software system and network protocol that provides a basis for graphical user interfaces and rich input device capability for networked computers...
(the graphics display and windowing framework upon which most Linux and BSD
Berkeley Software Distribution
Berkeley Software Distribution is a Unix operating system derivative developed and distributed by the Computer Systems Research Group of the University of California, Berkeley, from 1977 to 1995...
GUI
Graphical user interface
In computing, a graphical user interface is a type of user interface that allows users to interact with electronic devices with images rather than text commands. GUIs can be used in computers, hand-held devices such as MP3 players, portable media players or gaming devices, household appliances and...
s are based), Control-Alt-Backspace kills the X server
X Window System
The X window system is a computer software system and network protocol that provides a basis for graphical user interfaces and rich input device capability for networked computers...
—normally killing all programs using it (including the window manager
Window manager
A window manager is system software that controls the placement and appearance of windows within a windowing system in a graphical user interface. Most window managers are designed to help provide a desktop environment...
)—but not the underlying operating system. When a display manager is used, it restarts the killed X server.
Mac
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 ServerMac OS X Server
Mac OS X Server is a Unix server operating system from Apple Inc. The server edition of Mac OS X is architecturally identical to its desktop counterpart, except that it includes work group management and administration software tools...
logon screen, pressing -- will show an alert saying "This is not DOS."
Normal actions
Sleep Display:-–Sleep:-–
Quit all applications and restart:-–
Restart, Sleep or Shut Down (dialogue):-
Forced actions
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 lossData loss
Data loss is an error condition in information systems in which information is destroyed by failures or neglect in storage, transmission, or processing. Information systems implement backup and disaster recovery equipment and processes to prevent data loss or restore lost data.Data loss is...
.
Force Quit Applications
For windowed processes/applications, to present the Force Quit Applications dialogue:--- or use the Force Quit… command in the Apple menu.
Activity Monitor utility can quit, or force quit, any process.
Force the computer to restart
--Some Macs have a button.
Force the computer to shut down
- press the button for five seconds or more.
Apple II and Apple III
On the Apple IIeApple IIe
The Apple IIe is the third model in the Apple II series of personal computers produced by Apple Computer. The e in the name stands for enhanced, referring to the fact that several popular features were now built-in that were only available as upgrades and add-ons in earlier models...
, Apple IIc
Apple IIc
The Apple IIc, the fourth model in the Apple II series of personal computers, was Apple Computer’s first endeavor to produce a portable computer. The end result was a notebook-sized version of the Apple II that could be transported from place to place...
, and the Apple III
Apple III
The Apple III is a business-oriented personal computer produced and released by Apple Computer that was intended as the successor to the Apple II series, but largely considered a failure in the market. Development work on the Apple III started in late 1978 under the guidance of Dr. Wendell Sander...
, Control—Open-Apple—Reset would cause an immediate restart.
Equivalents on various platforms
| Platform | Key combination | Function |
|---|---|---|
| Acorn Acorn Computers Acorn Computers Ltd. was a British computer company established in Cambridge, England, in 1978. The company produced a number of computers which were especially popular in the UK. These included the Acorn Electron, the BBC Micro, and the Acorn Archimedes... Machines (pre-1987) |
Break | Processor reset, although confusingly always referred to as soft reset. Hold down Ctrl Control key In computing, a Control key is a modifier key which, when pressed in conjunction with another key, will perform a special operation ; similar to the Shift key, the Control key rarely performs any function when pressed by itself... as well for so-called hard reset (reinitializes various settings); hold down Shift Shift key The shift key is a modifier key on a keyboard, used to type capital letters and other alternate "upper" characters. There are typically two shift keys, on the left and right sides of the row below the home row... to boot from disk (or not to, if disk is the default). |
| Acorn and post-Acorn RISC OS RISC OS RISC OS is a computer operating system originally developed by Acorn Computers Ltd in Cambridge, England for their range of desktop computers, based on their own ARM architecture. First released in 1987, under the name Arthur, the subsequent iteration was renamed as in 1988... machines. |
Reset button | Processor reset, although confusingly always referred to as soft reset. Hold down Ctrl Control key In computing, a Control key is a modifier key which, when pressed in conjunction with another key, will perform a special operation ; similar to the Shift key, the Control key rarely performs any function when pressed by itself... as well for so-called hard reset (reinitializes various settings); hold down Shift Shift key The shift key is a modifier key on a keyboard, used to type capital letters and other alternate "upper" characters. There are typically two shift keys, on the left and right sides of the row below the home row... 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 Amiga The Amiga is a family of personal computers that was sold by Commodore in the 1980s and 1990s. The first model was launched in 1985 as a high-end home computer and became popular for its graphical, audio and multi-tasking abilities... |
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 Amstrad PCW The Amstrad PCW series was a range of personal computers produced by British company Amstrad from 1985 to 1998, and also sold under licence in Europe as the "Joyce" by the German electronics company Schneider in the early years of the series' life. When it was launched, the cost of a PCW system was... |
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 Atari ST The Atari ST is a home/personal computer that was released by Atari Corporation in 1985 and commercially available from that summer into the early 1990s. The "ST" officially stands for "Sixteen/Thirty-two", which referred to the Motorola 68000's 16-bit external bus and 32-bit internals... |
Ctrl + Alt + Del | Soft reset. Under FreeMiNT MiNT MiNT is a free software alternative operating system kernel for the Atari ST and its successors. Together with the free system components fVDI , XaAES , and TeraDesk , MiNT provides a free TOS compatible replacement OS that is capable of multitasking.MiNT was originally released by Eric Smith as... >= 1.16 it won't be instant, disk partitions are unmounted first. Ctrl + Alt + Shift + Del will perform hard reset. |
| IBM PC under DOS DOS DOS, short for "Disk Operating System", is an acronym for several closely related operating systems that dominated the IBM PC compatible market between 1981 and 1995, or until about 2000 if one includes the partially DOS-based Microsoft Windows versions 95, 98, and Millennium Edition.Related... |
Ctrl + Alt + Del | Perform a soft reboot |
| IBM PC under Windows 3.x Windows 3.1x Windows 3.1x is a series of 16-bit operating systems produced by Microsoft for use on personal computers. The series began with Windows 3.1, which was first sold during March 1992 as a successor to Windows 3.0... shell |
Ctrl + Alt + Del | Close unresponsive applications or (if pressed twice) perform a soft reboot |
| IBM PC under Microsoft Windows (95 Windows 95 Windows 95 is a consumer-oriented graphical user interface-based operating system. It was released on August 24, 1995 by Microsoft, and was a significant progression from the company's previous Windows products... , 98 Windows 98 Windows 98 is a graphical operating system by Microsoft. It is the second major release in the Windows 9x line of operating systems. It was released to manufacturing on 15 May 1998 and to retail on 25 June 1998. Windows 98 is the successor to Windows 95. Like its predecessor, it is a hybrid... , and Me Windows Me Windows Millennium Edition, or Windows Me , is a graphical operating system released on September 14, 2000 by Microsoft, and was the last operating system released in the Windows 9x series. Support for Windows Me ended on July 11, 2006.... ) |
Ctrl + Alt + Del | Bring up simplistic task manager Task manager A task manager is a program used to provide information about the processes and programs running on a computer, as well as the general status of the computer. It can also be used to terminate processes and programs, as well as change the processes priority... (actually "Close Program" dialog) or (if pressed twice) perform a soft reboot |
| IBM PC under Windows NT Windows NT Windows NT is a family of operating systems produced by Microsoft, the first version of which was released in July 1993. It was a powerful high-level-language-based, processor-independent, multiprocessing, multiuser operating system with features comparable to Unix. It was intended to complement... -based OS (NT Windows NT Windows NT is a family of operating systems produced by Microsoft, the first version of which was released in July 1993. It was a powerful high-level-language-based, processor-independent, multiprocessing, multiuser operating system with features comparable to Unix. It was intended to complement... , 2000 Windows 2000 Windows 2000 is a line of operating systems produced by Microsoft for use on personal computers, business desktops, laptops, and servers. Windows 2000 was released to manufacturing on 15 December 1999 and launched to retail on 17 February 2000. It is the successor to Windows NT 4.0, and is the... , XP Windows XP Windows XP is an operating system produced by Microsoft for use on personal computers, including home and business desktops, laptops and media centers. First released to computer manufacturers on August 24, 2001, it is the second most popular version of Windows, based on installed user base... , 2003, Vista Windows Vista Windows Vista is an operating system released in several variations developed by Microsoft for use on personal computers, including home and business desktops, laptops, tablet PCs, and media center PCs... and Windows 7) |
Ctrl + Shift + Esc | Bring up the Windows Task Manager Windows Task Manager Windows Task Manager is a task manager application included with the Microsoft Windows NT family of operating systems that provides detailed information about computer performance and running applications, processes and CPU usage, commit charge and memory information, network activity and... |
| Ctrl + Alt + Del | Also known as the Secure Attention Sequence Secure attention key A secure attention key is a special key or key combination to be pressed on a computer keyboard before a login screen must be trusted by a user. The operating system kernel, which interacts directly with the hardware, is able to detect whether the secure attention key has been pressed... ; bring up the logins screen (when pressed in login screen), or the "Windows security" dialog or (configurable on Windows 2000 Windows 2000 Windows 2000 is a line of operating systems produced by Microsoft for use on personal computers, business desktops, laptops, and servers. Windows 2000 was released to manufacturing on 15 December 1999 and launched to retail on 17 February 2000. It is the successor to Windows NT 4.0, and is the... and later) the Windows Task Manager Windows Task Manager Windows Task Manager is a task manager application included with the Microsoft Windows NT family of operating systems that provides detailed information about computer performance and running applications, processes and CPU usage, commit charge and memory information, network activity and... (when logged in) |
|
| IBM PC under OS/2 OS/2 OS/2 is a computer operating system, initially created by Microsoft and IBM, then later developed by IBM exclusively. The name stands for "Operating System/2," because it was introduced as part of the same generation change release as IBM's "Personal System/2 " line of second-generation personal... |
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 Linux Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds... |
Ctrl + Alt + Del | Signal the init process (usually configured to soft reboot) |
| Alt + SysRq SysRq System request is a key on keyboards for PCs that has no standard use. This key can be traced back to the operator interrupt key used on IBM 3270-type console keyboards of the IBM System/370 mainframe computer, which was used to cause the operating system such as VM/370 or MVS to allow the console... + 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 Operating system An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system... |
Ctrl + Alt + Del | Often (but not always) configured to reboot |
| Sinclair ZX Spectrum ZX Spectrum The ZX Spectrum is an 8-bit personal home computer released in the United Kingdom in 1982 by Sinclair Research Ltd... |
Break | Halted peripheral (cassette tape or printer) operations with the report D BREAK – CONT repeats, or halted BASIC BASIC BASIC is a family of general-purpose, high-level programming languages whose design philosophy emphasizes ease of use - the name is an acronym from Beginner's All-purpose Symbolic Instruction Code.... programs with the report L BREAK into program. |
| Sun Sun Microsystems Sun Microsystems, Inc. was a company that sold :computers, computer components, :computer software, and :information technology services. Sun was founded on February 24, 1982... workstation |
L1/Stop + A | Enter ROM monitor |
| Sun workstation (serial console) | Break | Enter ROM monitor |
| Alphas DEC Alpha Alpha, originally known as Alpha AXP, is a 64-bit reduced instruction set computer instruction set architecture developed by Digital Equipment Corporation , designed to replace the 32-bit VAX complex instruction set computer ISA and its implementations. Alpha was implemented in microprocessors... running OpenVMS |
Ctrl + P | Enter ROM Serial Console System Reference Manual The SRM firmware is the boot firmware written by Digital Equipment Corporation for computer systems based on the Alpha AXP microprocessor... or reboot, depending on setting in SRM |
| Apple II series Apple II series The Apple II series is a set of 8-bit home computers, one of the first highly successful mass-produced microcomputer products, designed primarily by Steve Wozniak, manufactured by Apple Computer and introduced in 1977 with the original Apple II... 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 Macintosh The Macintosh , or Mac, is a series of several lines of personal computers designed, developed, and marketed by Apple Inc. The first Macintosh was introduced by Apple's then-chairman Steve Jobs on January 24, 1984; it was the first commercially successful personal computer to feature a mouse and a... 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 Mac OS Mac OS is a series of graphical user interface-based operating systems developed by Apple Inc. for their Macintosh line of computer systems. The Macintosh user experience is credited with popularizing the graphical user interface... (7 and later) |
Option + Command + Esc | Force quit applications |
| S60 Platform S60 (software platform) The S60 Platform is a software platform for mobile phones that runs on Symbian OS. It was created by Nokia, who made the platform open source and contributed it to the Symbian Foundation. S60 has been used by mobile device manufacturers including Siemens mobile, Lenovo, LG Electronics, Panasonic... (used on some mobile phone Mobile phone A mobile phone is a device which can make and receive telephone calls over a radio link whilst moving around a wide geographic area. It does so by connecting to a cellular network provided by a mobile network operator... s such as Nokia Nokia Nokia Corporation is a Finnish multinational communications corporation that is headquartered in Keilaniemi, Espoo, a city neighbouring Finland's capital Helsinki... smartphone Smartphone A smartphone is a high-end mobile phone built on a mobile computing platform, with more advanced computing ability and connectivity than a contemporary feature phone. The first smartphones were devices that mainly combined the functions of a personal digital assistant and a mobile phone or camera... s) |
Green (call answer) + * + 3 (while restarting the phone) | Wipes internal memory and resets the device |
| SGI Silicon Graphics Silicon Graphics, Inc. was a manufacturer of high-performance computing solutions, including computer hardware and software, founded in 1981 by Jim Clark... 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 Commodore 64 The Commodore 64 is an 8-bit home computer introduced by Commodore International in January 1982.Volume production started in the spring of 1982, with machines being released on to the market in August at a price of US$595... & Vic-20 |
Run/Stop + Restore | Halt (soft reconfiguration) and return to READY prompt |
| Commodore 128 Commodore 128 The Commodore 128 home/personal computer was the last 8-bit machine commercially released by Commodore Business Machines... |
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 X Window System The X window system is a computer software system and network protocol that provides a basis for graphical user interfaces and rich input device capability for networked computers... |
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 TI-30 The TI-30 was a scientific calculator manufactured by Texas Instruments, the first model of which was introduced in 1976. While the original TI-30 left production in 1983 after several design revisions, TI maintains the TI-30 designation as a branding for its low and mid-range scientific... |
On + Clear | Restarts the calculator and clears RAM Ram -Animals:*Ram, an uncastrated male sheep*Ram cichlid, a species of freshwater fish endemic to Colombia and Venezuela-Military:*Battering ram*Ramming, a military tactic in which one vehicle runs into another... |
| TI-80 TI-80 TI-80 is a graphing calculator made by Texas Instruments. It was originally designed in 1995 to be used at a middle school level .The TI-80 featured the smallest screen and slowest processor of any TI graphing calculator. In comparison, the TI-81, released in 1990, featured a 2 MHz Zilog Z80... , TI-81 TI-81 The TI-81 is the first graphing calculator made by Texas Instruments. It was designed in 1990 for use in algebra and precalculus courses. Since its original release, it has been superseded several times by newer calculators - the TI-82, the TI-83, the TI-83 Plus, TI-83 Plus Silver Edition, the... , TI-82 TI-82 The TI-82 is a graphing calculator made by Texas Instruments. The TI-82 was designed in 1993 as a stripped down, more user friendly version of the TI-85, and as a replacement for the TI-81. It was the direct predecessor of the TI-83. It shares with the TI-85 a 6 MHz Zilog Z80 microprocessor... , TI-83, TI-84 |
Mode, Alpha, S | Shows ROM version number. [Enter] enters self test mode |
| TI-85 TI-85 The TI-85 was a graphing calculator made by Texas Instruments based around the Zilog Z80 microprocessor. Designed in 1992 as TI's second graphing calculator , it has since been replaced by the TI-86, which has also been discontinued.... , TI-86 TI-86 The TI-86 is a programmable graphing calculator introduced in 1997 and produced by Texas Instruments. The TI-86 uses the Zilog Z80 microprocessor. It is partially backwards-compatible with its predecessor, the TI-85.... |
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 Ram -Animals:*Ram, an uncastrated male sheep*Ram cichlid, a species of freshwater fish endemic to Colombia and Venezuela-Military:*Battering ram*Ramming, a military tactic in which one vehicle runs into another... Esc + On Force Break without restarting RAM Ram -Animals:*Ram, an uncastrated male sheep*Ram cichlid, a species of freshwater fish endemic to Colombia and Venezuela-Military:*Battering ram*Ramming, a military tactic in which one vehicle runs into another... |
| Many Natural Display Casio Casio is a multinational electronic devices manufacturing company founded in 1946, with its headquarters in Shibuya, Tokyo, Japan. Casio is best known for its electronic products, such as calculators, audio equipment, PDAs, cameras, musical instruments, and watches... Calculators |
Shift + 7 + On | Restarts the calculator and clears RAM Ram -Animals:*Ram, an uncastrated male sheep*Ram cichlid, a species of freshwater fish endemic to Colombia and Venezuela-Military:*Battering ram*Ramming, a military tactic in which one vehicle runs into another... and EEPROM EEPROM EEPROM stands for Electrically Erasable Programmable Read-Only Memory and is a type of non-volatile memory used in computers and other electronic devices to store small amounts of data that must be saved when power is removed, e.g., calibration... . Continue pressing Shift to advance through self-test mode. |
| TI-99/4A Texas Instruments TI-99/4A The Texas Instruments TI-99/4A was an early home computer, released in June 1981, originally at a price of USD $525. It was an enhanced version of the less-successful—and quite rare—TI-99/4 model, which was released in late 1979 at a price of $1,150... |
FCTN-+ | Resets machine back to startup screen. |
| Voyage 200 | 2nd + Hand + On | Restarts the calculator and clears RAM Ram -Animals:*Ram, an uncastrated male sheep*Ram cichlid, a species of freshwater fish endemic to Colombia and Venezuela-Military:*Battering ram*Ramming, a military tactic in which one vehicle runs into another... |
| 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 BeOS BeOS is an operating system for personal computers which began development by Be Inc. in 1991. It was first written to run on BeBox hardware. BeOS was optimized for digital media work and was written to take advantage of modern hardware facilities such as symmetric multiprocessing by utilizing... |
Ctrl-Alt-Shift and click an applications entry in the Deskbar | Kills application |
| Zenith Zenith Data Systems Zenith Data Systems was a division of Zenith founded in 1979 after Zenith acquired Heathkit, which had, in 1977, entered the personal computer market. Headquartered in Benton Harbor, Michigan, Zenith sold personal computers under both the Heath/Zenith and Zenith Data Systems names... 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 Olivetti Olivetti S.p.A. is an Italian manufacturer of computers, printers and other business machines.- Founding :The company was founded as a typewriter manufacturer in 1908 in Ivrea, near Turin, by Camillo Olivetti. The firm was mainly developed by his son Adriano Olivetti... M20 |
Ctrl + Reset | Soft resets the machine |
| TI Explorer TI Explorer The Texas Instruments Explorer is a family of Lisp Machine computers. These computers were sold by Texas Instruments in the 1980s. The Explorer is based on a design from Lisp Machines Incorporated, which is based on the MIT Lisp Machine.... Lisp Machine |
Left-Ctrl Left-Meta Right-Ctrl Right-Meta Abort | Restart the system |
| Xfce Xfce Xfce is a free software desktop environment for Unix and other Unix-like platforms, such as Linux, Solaris, and BSD – though recent compatibility issues have arisen with regard to BSD Unix platforms... |
Ctrl + Alt + Esc + click on window | Kill application |
| Foxtel Foxtel Foxtel is an Australian pay television company, operating cable, direct broadcast satellite television and IPTV services. It was formed in 1995 through a joint venture established between Telstra and News Corporation.... 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. |
| 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 IPod Touch The iPod Touch is a portable media player, personal digital assistant, handheld game console, and Wi-Fi mobile device designed and marketed by Apple Inc. The iPod Touch adds the multi-touch graphical user interface to the iPod line... , iPhone IPhone The iPhone is a line of Internet and multimedia-enabled smartphones marketed by Apple Inc. The first iPhone was unveiled by Steve Jobs, then CEO of Apple, on January 9, 2007, and released on June 29, 2007... , and iPad IPad The iPad is a line of tablet computers designed, developed and marketed by Apple Inc., primarily as a platform for audio-visual media including books, periodicals, movies, music, games, and web content. The iPad was introduced on January 27, 2010 by Apple's then-CEO Steve Jobs. Its size and... |
Top Power Button + Center Home Button (hold down until Apple logo shows) | 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 Nexus One The Nexus One was Google's flagship smartphone manufactured by Taiwan's HTC Corporation. It became available on January 5, 2010 and uses the Android open source mobile operating system... |
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 Motorola Droid The Motorola Droid is an Internet and multimedia enabled smartphone designed by Motorola, which runs Google's Android operating system. The Droid had been publicized under the codenames Sholes and Tao and the model number A855... and its successor Motorola Droid 2 The Motorola Droid 2 is the fifth phone in Verizon's Droid line. In the U.S., it is available exclusively on Verizon Wireless, and was released August 12, 2010 . It runs the Android operating system by Google, and can run Flash Player 10.1... |
See also
- WinlogonWinlogonIn computing, Winlogon is the component of Microsoft Windows operating systems that is responsible for handling the secure attention sequence, loading the user profile on logon, and optionally locking the computer when a screensaver is running...
— The Windows process that detects and responds to Ctrl+Alt+Del - Secure attention keySecure attention keyA secure attention key is a special key or key combination to be pressed on a computer keyboard before a login screen must be trusted by a user. The operating system kernel, which interacts directly with the hardware, is able to detect whether the secure attention key has been pressed...
- David BradleyDavid Bradley (engineer)David Bradley was one of the twelve engineers who worked on the original IBM PC, developing the computer ROM BIOScode. He is credited by some for inventing the "Control-Alt-Delete" key combination that was used to reboot the computer.-Control-Alt-Delete:...
, inventor of the Control-Alt-Delete combination for the original IBM PC.
- Parts of this article were originally based on the FOLDOCFree On-line Dictionary of ComputingThe Free On-line Dictionary of Computing is an online, searchable, encyclopedic dictionary of computing subjects. It was founded in 1985 by Denis Howe and is hosted by Imperial College London...
article Three-finger salute at FOLDOC, used with permission.
In popular culture
The keystrokes are well known and infamous for escaping from problems in pop culture. For example, in the Billy TalentBilly Talent
Billy Talent is a Canadian post-hardcore band from Streetsville, Ontario. They formed in 1993 with Ben Kowalewicz as the lead vocalist, Ian D'Sa on lead guitar, bassist Jon Gallant and drummer Aaron Solowoniuk ....
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."
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"
General references
- Linux manual pages for kill(2) and reboot(2). — a report of the effect of
LocalRebootin Windows 95 — a report of differences inLocalRebootbetween Windows 3.x and Windows 95