Editing Num lock

[[File:Num lock integrated LED.jpg|thumb|200px|Num lock key with integrated indicator [[LED]]]]

'''Num lock''' (also called '''Numpad lock''' or '''Numerics lock''') is a [[lock key]] introduced by IBM to permit the [[numeric keypad]] to also provide navigation functionality. With Num lock engaged, the numeric keypad would enter numbers. With Num lock disengaged, it would provide [[cursor keys]] and other navigation functionality.

==PC-compatible computers==
[[File:Lock LED cluster.jpg|200px|thumb|Typical LED cluster of a mid-90s keyboard]]

With the introduction of the [[IBM Enhanced Keyboard]], with its dedicated navigation clusters, Num lock no longer served any purpose on full-size desktop keyboards except backwards compatibility. However, the functionality has been retained ever since. Num lock is typically left permanently enabled on desktop computers running [[Microsoft Windows]] and [[Linux]]; often with Windows, it must be enabled when a Windows user account is created for the first time, and will remain enabled from that point on.

==Macintosh computers==
Apple have never provided numeric keypad-based cursor navigation on Macintosh computers, and the num lock legend on some Macintosh keyboards is simply there for compatibility with PC applications (for example PC emulation); under all variants of [[Mac OS]], the key serves as the [[clear key]].

==Numpad emulation==
Many compact keyboards, for instance on laptops, lack the space for a dedicated numeric keypad but many people are accustomed to entering numbers via the numeric keypad instead of the number row.
Many such compact keyboards therefore offer a special keyboard layer for the keypad on the regular alphanumeric keyboard and that layer is often enabled by a key that is called Num Lock.
Some [[tenkeyless]] keyboards also provide this functionality, including the [[Topre Realforce]].

Some laptops lack a num lock [[LED]], and it is not possible to visually determine whether num lock is engaged (changes in state are indicated momentarily by on-screen notification). This can cause problems for password entry at the logon desktop, when the keyboard is typing numbers instead of letters, and the user cannot tell.

Over [[PS/2]] and [[USB]], the state of the locking keys is host-controlled and the keyboard needs to be smart enough to send virtual Num lock key presses to influence the host's state to match the keyboard's intended state - but this does not always work.
To avoid that complexity and the risk for error, some PC keyboards therefore instead have a separate [[Pad lock]] key only to change the layer, with a separate Num lock key that works as on a regular full-size keyboard switching between numeric entry and navigation.

==Symbol==
Almost all Num lock key have textual legends. ISO/IEC 9995-7 mandates the symbol <span style="font-size:150%">⇭</span> but it is very unusual.

Lock lights tend to have a text legend, the word "Num", the word "Num" with a downwards arrow, the digit 1, the digit 1 with a downwards arrow or the digit 1 scribed inside a padlock symbol.

==See also==
* [[Numeric keypad]]
* [[Pad lock]]
* [[Clear key]]

[[Category:Lock keys]]