The physical layout of a keyboard describes the placement of keys on the keyboard.
The keyboard hardware assigns a binary scancode value to each key. The keyboard
hardware does not know or care what is engraved on the keytop.
Keyboards come in a variety of physical layouts. The most common client keyboards
are based on PC enhanced keyboards. The full keyboard layout, as shown in Figure
1, has 101 keys. This consists of a basic keypad, a row of function keys, a
cursor keypad, and a numeric keypad. This layout was introduced in 1984 and
is now standard for full size keyboards.
Figure 1: 101 Key Layout (US)
Reduced-size keyboards such as those on laptops leave off the numeric keypad
and move the cursor keypad and function keys to conserve space. Many client
keyboards now add three Windows keys in the row with the spacebar. Some keyboards
such as those used in retail, have a large number of additional function keys.
In dealing with globalization issues we can generally ignore all sections of
the keyboard except the basic keypad. The basic keypad is based on the layout
of keys in a typewriter. The keys in the various rows are offset because this
was required in mechanical typewriters.
Most keyboards for European languages are based on the 102 key layout. This
is similar to the 101 key layout, but adds a key to the right of the left shift
key. The enter key is changed in orientation, and the key above the enter key
is moved to left of the enter key.
Figure 2: 102 Key Layout (France)
The keyboards used for Japanese and Traditional Chinese are based on the 106
key keyboard. This adds two letter keys (from within the backspace and right
shift keys). It also adds three function keys along the space bar. These extra
function keys are used to control the Input Method Editor (IME).
Figure 3: 106 key layout (Japan)
When a key on the keyboard is pressed or released, the binary scancode is sent
to the operating system. The keyboard hardware also sends repeat events when
a key is held down. The keyboard hardware does not assign any meaning to the
pressing or releasing of a key. | 
