and   the   CTRL   and   ALT   keys   were   duplicated   and Keyboard   Operation placed  on  each  side  of  the  space  bar. The   101-key   enhanced   keyboard   has   four functional   areas: Typing   area Numeric   keypad Functions   keys 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. For example,   when   working   with   a   word   processing program,   depressing the    CTRL 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 computer. Keyboard   Compatibility 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 industry   standard. 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 microprocessor 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. Keyboard   Maintenance 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 2-5