Content deleted Content added
adding picture with keyboard |
→Windows NT: Clarified info for Windows XP, and last paragraph (shutting down computers), some minor grammar corrections |
||
Line 25:
=== Windows NT ===
[[Image:Windows Task Manager.PNG|thumb|The Windows Task Manager in Windows
[[Image:Drumline-taskman.JPG|thumb|The Windows Security Dialog in Vista. From here, the Task Manager can be launched.]]
In [[Windows NT]], and thus on its successors, including [[Windows 2000]], [[Windows XP]], [[Windows Server 2003]], [[Windows Vista]] and [[Windows Server "Longhorn"]], this keystroke combination is recognized (as special sort of a system-wide "keyboard hook") by the [[Winlogon]] process which in response instructs [[GINA]] 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 [[Windows Server ___domain|___domain]], 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 is Windows Vista and Windows Server Longhorn, regardless of whether or not the computer is part of a ___domain.
* If
** ** and the Welcome Screen and [[fast user switching]] are turned off, Ctrl+Alt+Del will open the [[Windows Security Dialog]], as described above.
The design of Windows NT is such that, unless security is already compromised in some other way, only the WinLogon process, a trusted system process, can receive notification of this keystroke combination (because the kernel remembers [[Process ID]] of WinLogon process and allows only that process registering it). This keystroke combination is thus a [[secure attention key]]. In Windows NT, it is called 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, 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 [[SysRq|System Request]] key), because on the PC platform no program could reasonably expect to redefine this keystroke combination for its own purposes.
Line 36 ⟶ 38:
It is also a reliable method for bringing up the Task Manager (in Windows Server 2003 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. It can be however disabled by Windows Group Policies. 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.
As a side effect, users that 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.
== OS/2 ==
| |||