A special function key is a keyboard key that performs an operation instead of—or in addition to—typing an ordinary character. The term often refers to the F1–F12 row or to secondary actions printed on those keys, such as adjusting volume or screen brightness. What happens when you press one depends on the keyboard’s mode, the computer model, and the active application.
What does “special function key” mean?
A function key is commonly one of the keys labelled F1, F2, and so on. Cambridge Dictionary defines a function key as “one of the keys at the top of the keyboard that make the computer perform particular operations” (Cambridge Dictionary).
“Special function key” can also mean a key’s secondary action, often represented by a small icon. Examples include volume, microphone, brightness, display selection, or wireless controls. These actions are distinct from typing letters, numbers, or punctuation.
Why can the same key do different things?
On some keyboards, keys in the F1–F12 row have a standard function-key action and a secondary action. The keyboard’s Fn mode determines which action occurs when you press a key on its own; holding Fn may invoke the other action. The exact arrangement varies by computer and keyboard, so an icon or mode indicator is more reliable than assuming one universal mapping.
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For example, Lenovo documents an Fn Lock mode that switches between standard F1–F12 actions and special actions such as volume and brightness. Lenovo’s guidance describes the switch as “fn + fnLock”; some model-specific Lenovo instructions describe Fn+Esc for changing the mode. These are vendor examples, not instructions that apply to every keyboard (Lenovo keyboard guidance; Lenovo ThinkPad user guide).
Can an application change what a function key does?
Yes. Software can assign actions to function keys, so the active application matters as well as the keyboard mode. In SAP’s ABAP Workbench documentation, for example, F1 opens field help and F4 opens input help. Those assignments describe that application context, not a universal behavior for those keys (SAP Help Portal documentation).
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How to tell what a key will do
- Check the keycap: Look for an F-number and any secondary-action icon.
- Check the mode: If the keyboard has Fn Lock, its state may determine whether a press triggers the F-key action or the icon action. The control and shortcut depend on the model.
- Consider the active app: A program may assign its own action to F1–F12.
- Consult the computer’s manual: The key layout and mode controls are model-specific; do not assume another brand’s Fn shortcut will work.
How special-purpose keys differ from character keys
Character keys enter text, while modifier keys—such as Shift or Ctrl—change how another key is interpreted. Special-purpose keys can instead trigger a direct operation, such as changing brightness, controlling sound, or powering a device. X.Org’s keyboard documentation gives brightness, power, and sound controls as examples of such actions (X.Org documentation).
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