A computer keyboard communicating to a computer monitor is an example of what kind of loop system?

Keyboard is only tools where end user is communicated with computer.

Explanation:

Even though some people user voice speech recognition tool or software to communicate to computer which is not so user friendly or not enabled for software programming.

Cursor blinks, which indicate waiting for end user to end the data. So end user enters data thru keyboard. Keyboard has inbuilt buffer cache which store last 16 character of end user input. So keyboard used a loop to enter or store last 16 characters.