https://copilot.microsoft.com/chats/5HFmkTCJPFQDhYPRggt5f 

Here's a simple example of a memory-resident keyboard handler written in Pascal. This code hooks into the keyboard interrupt vector to create a custom keyboard handler that can intercept and process keystrokes.

pascal

program MemoryResidentKeyboard;

uses
  Dos;

var
  OldInt09: Pointer;

procedure NewInt09; interrupt;
begin
  // Custom keyboard handling code goes here
  // Example: Intercept the 'A' key and replace it with 'B'
  if Port[$60] = $1E then // Scan code for 'A' key
  begin
    asm
      mov al, $30  // Scan code for 'B' key
      out $60, al
    end;
  end;

  // Call the original interrupt handler
  asm
    pushf
    call dword ptr OldInt09
  end;
end;

begin
  // Save the old interrupt vector and set the new one
  GetIntVec($09, OldInt09);
  SetIntVec($09, @NewInt09);

  // Keep the program resident in memory
  Keep(0);
end.

Here's a brief explanation of the code:

1. OldInt09: This variable stores the pointer to the original keyboard interrupt handler.

2. NewInt09: This is the custom interrupt handler that intercepts keystrokes. It checks if the 'A' key (scan code $1E) is pressed and replaces it with the 'B' key (scan code $30).

3. GetIntVec and SetIntVec: These procedures get and set the interrupt vector for the keyboard interrupt.

4. Keep: This procedure keeps the program resident in memory.

Feel free to adapt this code for your needs! If you have any specific requirements or further questions, just let me know. 😊

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