The first component is the monitor. The monitor takes the information from the video card, which is inside the computer's case. The monitor turns the information into the physical image that is seen on the screen.
The keyboard is the primary input device. Most of the time, when the BIOS starts, it must detect a keyboard in order to start.
The pointer is whatever moves the cursor. It is usually the mouse, but could also be a joystick, a trackpad, or a trackball.
The printer is a special output device, because it can translate data to paper.
Inside the case of the computer, there are many more working parts. Each component has a function. The case, or box, of the computer provides hard protection from the outside.