Unit 1 Wonderful Structure of a Microcomputer

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

In appearance, a microcomputer has threesimple and apparent parts: the main frame, the keyboard and the monitor. Inother words, if you own these parts, you would exactly have a computer. Acomputer system is composed of software and hardware in the light of itsworking mode. If we compare the hardware to a human body, then, the softwarewould be soul.

Just as a driver can't drive a car withoutdriving skills or the car itself, you can't control a computer withoutcontrolling techniques or the computer itself. The controlling techniques arecalled software, while computers themselves and related devices are calledhardware.

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

Primary Components of a Microcomputer

There are many types of microcomputers. Here,we will use an IBM Personal Computer (PC) to illustrate the primary componentsof a microcomputer. Other brands and models of microcomputers exhibitdifference between 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, allof which are hardwired to the main frame. The main frame is the heart of amicrocomputer system. It contains the Central Processing Unit (CPU), a chipthat controls the major operations of the computer and the main memory.

Floppy and Hard Disks

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

Most microcomputers use floppy diskettes of 51/4 inches and 3 1/2inches in diameter. The following figure shows a 3 1/2inches floppy diskette.

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

Keyboard and Mouse

A keyboard is a requisite hardware device ofa computer. It is an input device most in use, and a dialogue tool between aman and a computer. We can input data needed to be processed or preserved by acomputer via a keyboard.

A typical includes a group of standard keysset in the center of the keyboard, many function keys and several additionalkeys. Function and additional keys have different roles in different software.

Another popular input device is mouse. Themouse is a small, handheld object that is pushed around a desktop to move thecursor on the screen or to select choices from menus displayed on the screen. Amouse is essentially a pointing device that allows the user to do manyoperations more quickly than he could with the keyboard alone.

Monitor

The monitor is an essential output device ofa microcomputer. Monitors, also known as video display terminals (VDTs),resemble television screens, and may be either monochrome or color. Amonochrome monitor displays only one color on the screen. It is possible whiteor more eyepleasing green. While color monitors usually offer a wide selectionof display colors.

Printer

The printer is the most commonly used outputdevice after the monitor. Printers can create a permanent paper copy of resultsgenerated by the program being run on the computer. These printouts aresometimes referred to as hard copy. Printers can also generate listings ofprograms and graphic images. Three types of printers are available: wireprinters, ink jet printers and laser printers