In general, the I/O devices are a bridge between a user and a microcomputer. A microcomputer gets what the user types on the keyboard, the user sees what the computer writes on the printer or displays on the screen.
The disk storage is a special category of I/O that is intended for a computers own use. Information on a disk can be read and written only by the computer and it can not be read or written by users.
The microprocessor and the memory make up a closed world and the I/O devices open the world to the users. The computer communicates through I/O devices open the world to the users. The computer communicates through I/O devices. These devices include keyboard, display screen, mouse, printer, telephone line connected to the computer, and any other channels of communication into or out of the computer.
