What is input and output of a computer?

It can vary greatly. It depends on what you are trying to accomplish. For example, typing on a keyboard or click on a mouse is usually input to a computer. Input can also come from a computer file or another computer. When you clicked on the link to get this answer to your question, that click was input. The answer is essentially output. Output can be displayed on a screen like this answer. It can be a printout of a page or a file that is stored on a computer or other device like a thumb drive or sent to another computer.