sticking,   the   key   can   be   removed   and   cleaned   or replaced. MOUSE The   mouse   is   quickly   becoming   a   very   popular input  device.  Some  programs,  especially  graphic  user interface  (GUI)  programs,  virtually  require  a  mouse. Mice  are  available  in  several  shapes  and  sizes,  but all  operate  in  about  the  same  way.  The  mouse  case  is plastic  and  designed  to  fit  your  hand.  On  the  top  of the  mouse  are  two  or  more  buttons.  These  buttons  are used  to  indicate  to  the  computer  that  an  action  is desired  at  the  current  location  of  the  pointer.  For example,   one   popular   GUI   program   will   activate   a program  when  the  cursor  pointer  is  placed  over  a program   icon   and   the   left   mouse   button   is   pushed twice. If  you  turn  the  mouse  over,  you  will  see  a  small rubber  ball.  As  you  move  the  mouse  across  the  desk top,  this  ball  rolls  and  moves  the  encoders  inside  the mouse.  Remove  the  access  plate  and  remove  this  ball and  you  will  see  two  or  three  rollers.  These  are  the position  encoders  that  send  movement  data  to  the computer. Mouse   Connections A  mouse  can  be  connected  to  the  computer  in several   ways. These  are  the  mouse  port,  a  serial mouse,  and  a  bus  mouse. The  mouse  port  is  the  simplest  way  to  interface the   mouse   with   the   computer.   A   special,   dedicated port   is   built   into   the   motherboard   of   the   computer. The  mouse  is  plugged  directly  into  this  port. The  serial  mouse  is  plugged  into  one  of  the computer’s  serial  ports.  When  the  computer  is  booted, the   mouse   driver   searches   the   ports   to   determine which  port  the  mouse  is  connected  to. computer’s   expansion   slots. The   mouse   then communicates  with  the  computer  across  the  main  bus. Recently,  some  manufacturers  have  introduced  the cordless   mouse. The  cordless  mouse  requires  a special   interface   card   that   plugs   into   one   of   the expansion  slots.  The  mouse  is  equipped  with  a  small, low-power   radio   transmitter   that   transmits   mouse movements  to  the  interface  card.  The  receiver  on  the interface  card  decodes  the  signal  and  sends  it  to  the mouse   driver   program. Mouse   Maintenance A  mouse  requires  very  little  maintenance.  About the   only   maintenance   is   to   clean   the   mouse   if   the pointer   movement   is   erratic   or   jerky.   To   clean   the mouse,  turn  off  the  computer  and  remove  the  rubber ball.  Clean  the  ball  with  a  mild  detergent  and  water. Clean  the  encoder  rollers  with  a  lint-free  swab  and  a cleaning  solvent  such  as  denatured  alcohol.  Be  sure the  ball  is  completely  dry  before  reinstalling  it  and applying  power  to  the  computer. TRACKBALL The   trackball,   used   with   personal   computers,   is another  pointer  device  that  can  be  used  instead  of  the mouse.  A  trackball  is  basically  a  mouse  turned  over and  the  ball  exposed.  The  user  rolls  the  ball,  moving the  pointer  on  the  screen.  The  trackball  operates  the same   way   the   mouse   does.   Many   laptop   computers are  being  manufactured  with  a  trackball  installed  in the  keyboard,  eliminating  the  need  for  an  external mouse.  Full-size  keyboards  are  also  available  with  a built-in   trackball. SUMMARY-PERSONAL   COMPUTER   VIDEO DISPLAYS   AND   INPUT   DEVICES This   chapter   has   presented   material   about   video display   monitors,   video   adapters,   and   their   input devices. The   following   information   summarizes important  points  you  should  have  learned. The  bus  mouse  is  for  users  that  do  not  have  a  free serial  port. The  mouse  is  plugged  into  a  special interface  board  that  is  installed  into  one  of  the 2-6 . . .