and the CTRL and ALT keys were duplicated and
placed on each side of the space bar.
The 101-key enhanced keyboard has four
Cursor and screen controls
The typing area is the main section of the
keyboard and is setup similar to a standard typewriter
keyboard. The CTRL and ALT keys, located on
either side of the space bar, allow the programmer to
add additional meaning to standard keys.
example, when working with a word processing
and I keys
simultaneously may cause a macro program to run
that will turn the italics font on or off.
The numeric keypad is located on the right side of
the keyboard. It contains the 10 numeric keys (0 - 9),
the keys required for addition (+), subtraction (-),
multiplication (*) and division (/). An additional
ENTER key was added to the numeric keypad to ease
operation. Just like the 84-key keyboard, the numeric
keypad can also be used for cursor and screen control
when not in the NUMLOCK (number lock) mode.
The function keys are located in groups of four
across the top of the typing area of the keyboard. The
escape (ESC) key is in the top left corner and
dedicated PRINTSCRN/SYSREQ, SCROLL LOCK,
and PAUSE/BREAK keys are provided for these
commonly used functions.
The cursor and screen control keys are located
between the typing area and the numeric keypad. The
cursor control keys are located on the bottom in an
inverted T pattern. Above the cursor control keys are
the INSERT, HOME, PAGE UP, DELETE, END, and
PAGE DOWN keys.
Two types of switches are used in keyboards.
Most keyboards use microswitches for each key
position. Depressing a switch sends the position data
of that switch to the computer.
The other type of keyboard switch is the
capacitive keyboard. The bottom of the keyboard is
one large capacitor. Pushing a key switch pushes a
paddle into the capacitive module, changing the
capacitance of the module. This signal is interpreted
by the keyboard microprocessor and sent to the
The original IBM PC and XT computers came
equipped with an 83-key keyboard. When IBM
introduced the AT computer, it came with a new 84-
key keyboard. Later, the 101-keyboard was introduced
with newer AT computers and has become the
The 84-key keyboard uses a
different keyboard microprocessor than its 83-key
predecessor and is not interchangeable. Many third
party keyboard manufacturers have overcome this
problem by enhancing the keyboard microprocessor
and adding a switch on the bottom of the keyboard.
This switch, marked AT/AX selects the system with
which the keyboard is to be used. The keyboard
then executes the proper routines.
Many 101-key keyboards are also equipped with an
AT/XT SELECT switch.
A computer that was
originally equipped with an 84-key keyboard should
accept a 101-key enhanced keyboard. If a 101-key
keyboard is installed on a computer that was
originally equipped with an 84-key keyboard and the
new keys (Fl1, F12, etc.) do not function, then the
ROM BIOS needs to be upgraded.
Maintenance of keyboards consists of periodically
cleaning the keyboard. Turn the keyboard over and
gently shake it to dislodge any loose dirt. The
keyboard can also be blown out with dry compressed
air. If a microswitch-type keyboard has a key that is