Chapter 18: Keyboards, Mice, and Pointing Devices^449
Number/cursor keys When theNUM LOCKis toggled on (and theNUM LOCK
LED is lighted), the ten number keys type the digits 0 to 9. When theNUM LOCK
is toggled off (the LED is off), these keys become cursor control keys. Most
keyboards with 101 keys or higher include keys for diagonal movement, which
are typically the 1, 7, 9, and 3 keys (without theNUM LOCKkey on) that move
down-left, up-left, up-right, and down-right, respectively.
INSERT/DELETE These two keys are the zero and period of the number pad
when it is in number mode; in cursor control mode, they duplicate the actions
of theINSERTkey and theDELETEkeys.
ENTER This is a secondENTERkey that remains anENTERkey regardless of
the number pad’s mode.Function Keys
The12keysonthetoprowofthekeyboardarethefunctionkeys,showninFigure18-8.These
keys have no default functions and are completely controlled by software, whether it is the
operating system or an application. Some software applications make extensive use of the
function keys, such as WordPerfect (a word processing system from Corel). For example, on
the DOS and Windows command line, theF3 key (all function keys are designated with anF
to differentiate them from the number keys) is used to repeat the last line entered, and in
virtually all Windows applications, theF1 key is used to open the Help system.
The earliest PCs had ten function keys that were arranged to the left side of the key-
board is two columns of five keys. When the enhanced keyboards were introduced, the
keys were expanded to twelve keys and placed along the top edge of the keyboard.
Figure 18-7. The number pad on a standard keyboard