This generally varies, depending on what you consider as an ‘input’. You can either keep it simple by just connecting, a keyboard and mouse. Or you could go ahead and add in as many input devices as you want as per your requirement. For example, a gaming fanatic may have a mouse, a camera, an Xbox controller, sensors, 3D printers, and an Ethernet wireless connection connected to the computer system. For more details, you can read the user manual that comes with the computer device.