A keyboard is a requisite hardware device of a computer. It is an input device most in use, and a dialogue tool between a man and a computer. We can input data needed to be processed or preserved by a computer via a keyboard. A typical includes a group of standard keys set in the center of the keyboard, many function keys and several additional keys. Function and additional keys have different roles in different software. Another popular input device is mouse. The mouse is a small, handheld object that is pushed around a desktop to move the cursor on the screen or to select choices from menus displayed on the screen. A mouse is essentially a pointing device that allows the user to do many operations more quickly than he could with the keyboard alone.
The monitor is an essential output device of a microcomputer. Monitors, also known as video display terminals (VDTs), resemble television screens, and may be either monochrome or color. A monochrome monitor displays only one color on the screen. It is possible white or more eyepleasing green. While color monitors usually offer a wide selection of display colors.
The printer is the most commonly used output device after the monitor. Printers can create a permanent paper copy of results generated by the program being run on the computer. These printouts are sometimes referred to as hard copy. Printers can also generate listings of programs and graphic images. Three types of printers are available: wire printers, ink jet printers and laser printers.