In Chinese, a computer is popularly known as an " electrical brain", for the working process of a computer is similar to a human brain very much.

     In appearance, a microcomputer has three simple and apparent parts: the main frame, the keyboard and the monitor. In other words, if you own these parts, you would exactly have a computer. A computer system is composed of software and hardware in the light of its working mode. If we compare the hardware to a human body, then, the software would be soul.

    Just as a driver can't drive a car without driving skills or the car itself, you can't control a computer without controlling techniques or the computer itself. The controlling techniques are called software, while computers themselves and related devices are called hardware.

   The work of a computer is just making full use of various resources by software set in the computer, and directing the hardware to realize marvelous omnipotent functions.

  There are many types of microcomputers. Here, we will use an IBM Personal Computer (PC) to illustrate the primary components of a microcomputer. Other brands and models of microcomputers exhibit difference in appearance and operations. An IBM PC is shown in the figure. Its primary hardware components are the main frame, the monitor, the keyboard, and many peripherals such as the disk drive, hard disk, printer, and mouse, all of which are hardwired to the main frame. The main frame is the heart of a microcomputer system. It contains the Central Processing Unit (CPU), a chip that controls the major operations of the computer and the main memory.

    The typical secondary storage medium of a microcomputer is the floppy and hard disks. A floppy disk, or diskette, is a thin circular piece of flexible polyester coated with a magnetic material. The data are recorded on a series of concentric circles called tracks. The access mechanism steps from track to track, reading or writing one track at a time. A track is subdivided into sectors. To distinguish the sectors, they are sequentially addressed by natural numbers 0,1,2and so on .A sector is a primitive access unit.

    Most microcomputers use floppy diskettes of 5 1/4 inches and 3 1/2inches in diameter. The following figure shows a 3 1/2 inches floppy diskette.

   Hard disks, or fixed disks, can be either fixed in the mainframe as a part of the internal hard disks reside permanently within the microcomputer and are removed only for servicing or replacement. External hard disks can be purchased alone and then attached to the microcomputer with cables; they are used for backing up large amounts of data or for additional storage capacity. Hard disks provide tremendous storage capacities ranging from hundreds of megabytes to several gigabytes.

   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.