Get character
Reads a character from the screen.
A1 [in,1u]
A2 [in,1u]
A3 [out,1u(char)]
A4 [out,1b]
A5 [out,1b]
BX [in,4u]
BY [in,4u]
CX [out,4u(XRGB)]
CY [out,4u(XRGB)]
This message allows you to get a character from the screen in the text mode.