How are characters r displayed on the monitor when i press a switch on the keeyboard?

Answer:

The upright sends a bitstream representing the character to the computer. The current interface program receive the information and then uses it's font map interface to send the personality to the screen.
keyboards enjoy different types but have like inputing technique, it uses a sesnsor to send message to the CPU for processing and consequently displayed to the monitor, when a corresponding key is pressed, it touches the sensor at the bottom to convey signals