Keyboard Routines

Below the routines that have to do with the keyboard will be described

• KBD_Install -- Installs our Keyboard Handler. These handlers are based off of the routines we wrote in MP3.

  ; ----------------------------------------------
  ; KBD_Install
  ;
  ; Inputs: None
  ;
  ; Outputs: OldKBV -- This will hold the vector to the old keyboard handler
  ;
  ; Input/Output: Nothing.
  ;
  ; Purpose: This function just sets the call back function of INT 1 to be our
  ; interrupt using INT 21h calls.
  ;
  ; Written by: Nathan Hamstra.
  ;
  ; This function is cut and pasted from Nathan's KBD_Install routine that he
  ; wrote for MP3.
  ; -----------------------------------------------

• KBD_Handler -- This routine is called by the interrupt and will update the keyboard status word.

  ; ----------------------------------------------
  ; KBD_Handler
  ;
  ; Inputs: The key presses and releases
  ;
  ; Outputs: KBDStatus -- Will be update corresponding to the key pressed.
  ;
  ; Input/Output: Nothing.
  ;
  ; Purpose: Modifies the kbdstatus to show what keys are currently held
  ; down
  ;
  ; Written by: Nathan Hamstra
  ; -----------------------------------------------

• KBD_Uninstall -- This routine will restore the original keyboard handler to oldKBDV

  ; ----------------------------------------------
  ; KDB_Uninstall
  ;
  ; Inputs: oldKBDV -- segment:offset of original keyboard handler
  ;
  ; Outputs: KBDStatus -- Will be update corresponding to the key pressed.
  ;
  ; Input/Output: Nothing.
  ;
  ; Purpose: Restores the vector table to original condition
  ;
  ; Written by: Nathan Hamstra
  ;
  ; This function is cut and pasted from Nathan's KBD_Uninstall routine that he
  ; wrote for MP3.
  ; -----------------------------------------------

• PlayerMov -- This function analyzes the KbdStatus variable and changes the appropriate values for the player movement

  ; ----------------------------------------------
  ; PlayerMov
  ;
  ; Inputs: kbdstatus == current status of the keyboard
  ;
  ; Outputs: carry flag if we need to exit
  ;
  ; Input/Output: player row and column position and status
  ;
  ; Purpose: Analyzes the kbdstatus word and changes the appropriate
  ; parameters of the player
  ;
  ; Written by: Nathan Hamstra
  ;
  ; -----------------------------------------------

• KbdReset -- This function resets the KbdStatus variable

  ; ----------------------------------------------
  ; KbdReset
  ;
  ; Inputs: None
  ;
  ; Outputs: None
  ;
  ; Input/Output: None
  ;
  ; Purpose: This simply reinitializes the kbdstatus variable
  ;
  ; Written by: Nathan Hamstra
  ;
  ; -----------------------------------------------

Keyboard Variables

Below all the variables that will be used in the keyboard routines will be described.

• oldKBDV -- Will hold the original keyboard interrupt handler.
• KbdStatus -- Will contain the status of all the keys.
• KBdJumpTable -- This variable is a jump table which allows faster handling of the keyboard interrupts.