KEYBOARD is a read-only numerical system variable that gets updated once every frame (sixtieth of a second).
When no key on the Petit Computer virtual keyboard is pressed,
KEYBOARD has a value of 0. When a key is pressed, it becomes the corresponding value in the Key Scan Codes list for one frame, then becomes 0 again. If the key remains 'pressed', the corresponding value will appear again 30 frames after the initial detection, then 35, then 40, etc..
The 5 'function keys' at the top of the lower screen, "
5RUN" do not count as 'keys' (the system variable FUNCNO detects these buttons), nor does the "X" at the top-right, the "ESC" 'key', or anything in the green bar at the bottom of the screen.