PC Hardware A Beginner’s Guide

(^450) PC Hardware: A Beginner’s Guide
Special-Purpose Keys
A few other keys on the keyboard are used only for very special purposes, if at all. Some
users rarely or never use these keys because not all applications support them or their
functions just do not come up in most data processing situations. These special-purpose
keys are:

ESC The Escape key is typically enabled as an exit key by most software
applications. It is used to cancel out of a command or to exit an application.
It is also used in combination with other keys to create special key values and
to indicate other actions. For example, in Windows theESCkey can be used to
close a context menu.
 PRINT SCREEN/SYSRQ ThePRINT SCREENmode of this key got its name back in
the MS-DOS days, when pressing it sent the image of the display to the printer.
On a Windows system, the image of the monitor’s display is sent to the Windows
Clipboard. Figure 18-9 illustrates the contents of the Windows Clipboard
Viewer after thePRINT SCREENkey was pressed with a Web browser on the
screen. The alternate mode of this key is a system request action. This key has
no real function on most PCs unless the PC is emulating an IBM terminal
connected to a mainframe computer.
 PAUSE/BREAK In its default mode (PAUSE), this key will, if enabled by
software, pause the display or the action of an application program. If used in
combination with theCTRLkey, the alternate mode of this key interrupts or
halts some software programs, primarily MS-DOS commands and applications.
Using theCTRLandBREAKkeys together is the same using theCTRLand C keys
to break an action.
Figure 18-8. The function keys on a standard keyboard