Since most modern desktop computers have a full-size keyboard with both a numeric pad and separate arrow keys, Num Lock is rarely used (always on) for its original purpose and often ends up confusing the user if it has for some reason been turned off without the user being aware of this. On some laptop computers, the Num Lock key is absent and replaced by the use of a key combination.
On some laptop computers, the Num Lock key is used to convert part of the main keyboard to act as a (slightly skewed) numeric keypad rather than letters. Num Lock would be used to select between the two functions. Most earlier computer keyboards had different number keys and cursor control keys however, to reduce cost, IBM chose to combine the two in their early PC keyboards. The Num Lock key exists because earlier 84-key IBM PC keyboards did not have cursor control or arrows separate from the numeric keypad. Its state (on or off) affects the function of the numeric keypad commonly located to the right of the main keyboard and is commonly displayed by an LED built into the keyboard.
It is a lock key, like Caps Lock and Scroll Lock. Num Lock or Numeric Lock ( ⇭) is a key on the numeric keypad of most computer keyboards. A keyboard with Num Lock turned on as indicated by an LED
