BIOS Data Area Keyboard Flags [0040:0017]
 Bit Description
 --- -------------------------------------------------------------------
  0  Right shift down
  1  Left shift down
  2  Ctrl down
  3  Alt down
  4  Scrollock on
  5  Numlock on
  6  Capslock on
  7  Insert mode on
  8  Left control down
  9  Left alt down		   PCjr : ctrl-alt-capslock held
  A  System request down	   PCjr : keyboard click active
  B  Ctrl-numlock (pause) toggled
  C  Scrollock down
  D  Numlock down
  E  Capslock down
  F  Insert down