(翻译)The term monitor is used interchangeably with screen,video display screen, and cathoderay tube. This output device provides your principal visual contact with the microcomputer system. When you enter commands or data from the keyboard,you see the results on the monitor. A monochrome monitor displays text and ,in some cases,graphics in a single color—commonly green or amber—usually on a dark background. A color monitor,often referred to as an RGB monitor(for red ,green,blue),can display text and graphics in various colors. Most of the capabilities of the monitor,including image clarity and the ability to draw graphics,are determined by the sophistication of the video display circuit board,if any, contained within the system unit. In any case, the user needs the appropriate software to take advantage of a monitor’s capabilities—including the ability to display graphics.
The main computer system cabinet, called the system unit, usually houses the power supply, the system board, and the storage devices(although some storage devices—disk drives, for example—are often housed in cabinets outside the system unit). These elements can be defined as follows:
(1) The power supply provides electrical power to all components housed in the system unit. In some microcomputers, it also provides power to the monitor.
(2) The system board, also known as the motherboard, is the main circuit board of the microcomputer system. It normally includes the microprocessor chip, main memory chips, all related support circuitry, and the expansion slots where additional components can be plugged in.
(3) The storage devices are usually one or more floppy disk drives and high-capacity hard disk drives. A floppy disk, or diskette, is a thin plastic disk enclosed in a paper or plastic covering that can be magnetically encoded with data. Hard disks are rigid disks capable of storing much more data than a floppy disk. Hard disks are more expensive than floppy disks. Since most hard disks are permanently installed in the system unit. Floppy disks, which can be carried around, are often used to move data from one computer to another.
(4) Additional components: the expansion slots on the system board allow users to add new components to their computer systems. The most popular add-on components include: a memory card containing main memory chips that give you additional main memory; an internal modem to facilitate data communications between computers over phone lines and similar cables; a batter-powered clock ad calendar mechanism; additional printer ports(hook-ups)that allow you to communicate with several types of output devices; and video display boards.
A computer virus is a computer program that is created to make and spread copies of itself. The program may however also be designed to have other effects on the systems it infects, ranging from the annoying to the disastrous.
Virus attacks are growing rapidly these days. According to BusinessWeek, the 76,404 attacks reported in the first half of 2003 nearly match previous year's total number . As new antivirus tools are more powerful than before, the virus writers are getting a lot smarter with newer and creative ways to attack network systems. Let's first examine some common virus types:
Basic Virus - a piece of software code that is developed to attack computers and network systems via email or Internet connections. It quickly replicates itself and gradually attaches to files, programs or the hard drive.
Trojan Horses - This is a program that doesn't replicate when entering a system but can be effectively used to open 'back doors.' Trojan Horses allow hackers to take control over a particular system or to steal very important data.
Worm - this type of virus is able to spread itself automatically over the network from one computer to the next. During a worm attack, users' computers get infected without even having to click open email attachment or any program, etc.
Since it is very difficult to avoid the virus, your best defense is a powerful antivirus program. In order to fight with such viruses, the software vendors should focus on making their products more robust. This may ask for a trade-off between user-friendliness and security. In specific cases it may require line-by-line inspection, code retooling and even systems automation to defend the installed programs.
Choose the best answer according to the passage
1)．A computer virus is a computer program that is created to make and spread of itself.
A．programs B．virus C．copies D．files
2)．Worm spread itself except by
A．network B．E-mail C．program D．hardware
3)．Antivirus program can scan and virus.
A．clean B．produce C．replicate D．make
4)．Trojan Horses .
A．quickly replicate itself and gradually attache to files, programs or the hard drive.
B．infect the computer without even having to click open email attachment or any program.
C．allow hackers to take control over a particular system or to steal very important data.
D．avoid the virus to attack computer.
5)．According to BusinessWeek, the attacks reported in the first half of 2003 nearly match previous year's total number .
A． 86,404 B．
