Num lock
Encyclopedia
Num Lock is a key on the numeric keypad
Numeric keypad
A numeric keypad, numpad or tenkey for short, is the small, palm-sized, seventeen key section of a computer keyboard, usually on the very far right. The numeric keypad features digits 0 to 9, addition , subtraction , multiplication and division symbols, a decimal point and Num Lock and Enter keys...

 of most computer keyboard
Computer keyboard
In computing, a keyboard is a typewriter-style keyboard, which uses an arrangement of buttons or keys, to act as mechanical levers or electronic switches...

s. It is a toggle key, like Caps Lock
Caps lock
Caps lock is a key on many computer keyboards. Pressing it sets an input mode in which typed letters are uppercase by default. The keyboard remains in caps lock mode until the key is pressed again...

 and Scroll Lock
Scroll lock
Scroll lock is a keyboard button on some computer keyboards. The key is not frequently used and therefore some keyboards lack Scroll Lock altogether....

. Its state is commonly represented by an LED
LEd
LEd is a TeX/LaTeX editing software working under Microsoft Windows. It is a freeware product....

 light built into the keyboard.

The Num Lock key exists because earlier 84-key IBM PC keyboard
IBM PC keyboard
The keyboards for IBM PC compatible computers are standardized. However, during the 3-plus decades of PC architecture being constantly updated, multiple types of keyboard layout variations have been developed....

s did not have arrows separate from the numeric keypad. Num Lock would be used to choose between the two functions. On some laptop computers, Num Lock keys are used to convert part of the main keyboard to act as a (slightly skewed) numeric keypad rather than letters. On some laptop computers, the Num lock key is excluded entirely and requires a key combination to activate.

Since most modern desktop computers have a full-size keyboard with both a numpad and separate arrow keys, Num Lock is rarely used for its original purpose, and ends up confusing the user if the computer has for some reason activated or deactivated the Num Lock key without the user being aware of it. This can be more of an issue on most laptop computers, since activating the Num Lock function typically requires use of the Fn key
Fn key
Fn, or 'Function', is a modifier key on many keyboards, especially on laptops, used in a compact layout to combine keys which are usually kept separate. It is typically found on laptops, since a full-sized keyboard would be difficult to fit in a laptop chassis. It is also found in many full-sized...

 and if a user accidentally switches it on they may have no idea how to switch it off. If a full-size keyboard is plugged into a laptop keyboard, then the Num Lock function is normally off, and the user would have to activate the Num Lock function to use the numeric keypad for numeric entry. Since Apple keyboard
Apple keyboard
The Apple Keyboard is a keyboard designed by Apple first for the Apple line, then the Macintosh line of computers. It is available in both wired and Bluetooth models.- Layout :...

s have always had dedicated arrow keys, Apple has keyboards that offer a separate numeric keypad may have no Num Lock key or a non-functional Num Lock key.
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