【文章內(nèi)容簡介】 as well as the control signals between the CPU and input/output devices.The ALU performs all the arithmetic and logical(parison) functions—that is, it adds, subtracts, multiplies, divides, and does parison. These parisons, which are basically “l(fā)ess than”, “greater than”, and “equal to”, can be bined into several mon expressions, such as “greater than or equal to”. The objective of most instructions that use parisons is to determine which instruction should be executed next. (二) Tell whether the following statements are true(T) or false(F) according to the passage A(根據(jù)上文的內(nèi)容判斷下列句子的正誤)(10%)1. With the development of puter, the physical size of the CPU has often bee bigger and bigger. ( )2. The movement of electronic signals between main memory and the ALU as well as the control signal between the CPU and input/output devices are controlled by the control unit of the CPU. ( )3. The CPU prises the control unit and memory. ( )4. The control unit performs all the arithmetic and logical functions. ( )5. The central processing unit (CPU) is the heart of the puter systems. ( )Passage BA puter virus is a puter 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 Business Week, the 76,404 attacks reported in the first half of 2003 nearly match previous year39。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. Let39。s first examine some mon virus types: Basic Virus a piece of software code that is developed to attack puters and network systems via or Internet connections. It quickly replicates itself and gradually attaches to files, programs or the hard drive.Trojan Horses This is a program that doesn39。t replicate when entering a system but can be effectively used to open 39。back doors.39。 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 puter to the next. During a worm attack, users39。 puters get infected without even having to click open 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 tradeoff between userfriendliness and security. In specific cases it may require linebyline inspection, code retooling and even systems automation to defend the installed programs.(三) Choose the best answer according to the passage B(根據(jù)上文的內(nèi)容選擇正確的答案)(10%)1．A puter virus is a puter program that is created to make and spread _________of itself.A. programs B. virus C. copies D. files2．Worm spread itself except by_________. .A. network B. Email C. program D. hardware3．Antivirus program can scan and_________ virus. A. clean B. produce C. replicate D. make 4．Trojan Horses_________ .A．quickly replicate itself and gradually attach to files, programs or the hard drive.B．infect the puter without