layouts

A keyboard layout is any specific mechanical, visual, or functional arrangement of the keys, legends, or key-meaning associations (respectively) of a computer, typewriter, or other typographic keyboard.
Mechanical layout is the placements and keys of a keyboard. Visual layout is the arrangement of the legends (labels, markings, engravings) that appear on the keys of a keyboard. Functional layout is the arrangement of the key-meaning association or keyboard mapping, determined in software, of all the keys of a keyboard.
Modern computer keyboards are designed to send a scancode to the operating system (OS) when a key is pressed, which is not necesarily the specific character engraved on that key. The OS converts the scancode into a specific binary character code using a "scancode to character" conversion table, called the keyboard mapping table. This means that a physical keyboard may be dynamically mapped to any layout without switching hardware components – merely by changing the software that interprets the keystrokes. Often, a user can change keyboard mapping in system settings. In addition, software may be available to modify or extend keyboard functionality. Thus the symbol shown on the physical key-top need not be the same as what goes into a document being typed.

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