Text 2. THE CPU MAIN COMPONENTS

As it is known the two functional units of the CPU are the control unit (CU) and the arithmetic-logical unit (ALU). The control unit manages and coordinates the entire computer sys­tem. It obtains instructions from the program stored in main memory, interprets the instructions, and issues signals that cause other units of the system to execute them.

The control unit operates by reading one instruction at a time from memory and taking the action called for by each instruc­tion. In this way it controls the flow between the main storage and the arithmetic-logical unit.

The control unit has the following components: a counter that selects the instructions, one at a time, from memory; a reg­ister that temporarily holds the instructions read from memory while it is being executed; a decoder that takes the coded instruc­tion and breaks it down into individual commands necessary to carry it out; a clock, which produces marks at regular intervals. These timing marks are electronic and very rapid.

The sequence of control unit operations is as follows. The next instruction to be executed is read out from primary stor-

Английский язык. Основы компьютерной грамотности 104

age into the storage register. The instruction is passed from the storage register to the instruction register. Then the operation part of the instruction is decoded so that the proper arithmetic or logical operation can be performed. The address of the op­erand is sent from the instruction register to the address regis­ter. At last the instruction counter register provides the address register with the address of the next instruction to be executed.

The arithmetic-logical unit (AL U) executes the processing op­erations called for by the instructions brought from main mem­ory by the control unit. Binary arithmetic, the logical operations and some special functions are performed by the arithmetical-logical unit.

Data enter the ALU and return to main storage through the storage register. The accumulator serving as a register holds the results of processing operations. The results of arithmetic op­erations are returned to the accumulator for transfer to main storage through the storage register. The comparer performs log­ical comparisons of the contents of the storage register and the accumulator. Typically, the comparer tests for conditions such as "less than", "equal to", or "greater than".

So as you see the primary components of the arithmetic-log­ical unit are banks of bistable devices, which are called regis­ters. Their purpose is to hold the numbers involved in the cal­culation and hold the results temporarily until they can be tranferred to memory. At the core of the ALU is a very high-

105 Unit 8. Central Processing Unit

speed binary adder, which is used to carry out at least the four basic arithmetic functions (addition, subtraction, multiplication and division). The logical unit consists of electronic circuitry which compares information and makes decisions based upon the results of the comparison.

9. Ответьте на вопросы, используя информацию текста.

1. What are the functional units of CPU? 2. What is the func­tion of CU? 3. How does CU operate? 4. What is the function of a counter? 5. What role does a decoder play? 6. What is the sequence of CU operations? 7. What is the function of the arith­metic-logical unit? 8. What operations are performed by ALU?

9. What primary components does ALU consist of? 10. What is
the function of an accumulator / comparer?

10. Найдите в тексте английские эквиваленты следующих
словосочетаний:

Функциональные блоки; устройство управления; ариф­метико-логическое устройство; управлять работой всей системы; получать команды; основная память; посылать сигналы; считывать команды поэтапно; таким образом; временно сохранять информацию; производить пометки через равные промежутки времени; последовательность операций; регистр памяти; регистр команд; адресный ре­гистр; счетчик; датчик; дешифратор; адрес операнда; ад­ресный регистр, высокоскоростной двоичный сумматор; по крайней мере; вычитание; сложение; умножение; деле­ние; принимать решения; результаты сравнения.

П. Вспомните значение новых слов и попытайтесь пере­вести словосочетания, употребляемые с этими словами.

Register, address register; base register; clock register; com­mand / instruction register; counter register; CPU register; hard­ware register; input / output register; memory register; operand register; general-purpose register; special-purpose register.

Counter binary counter; character counter; data counter; instruction counter; pulse counter; sequence counter; storage counter; software counter; time-out counter.

Selection: color selection; directory selection; drive selection; file selection; function selection; keyboard selection; menu se­lection; security selection.

Английский язык. Основы компьютерной грамотности 106

Management: data management; database management; disk management; error management; information management; memory management; network management; resource manage­ment; task management; window management.

12. Найдите в текстах 1 и 2 слова, близкие по значению
следующим:

Verbs: to work; to control; to receive; to keep; to send; to perform; to demand; to choose; to supply; to pass; to name; to include; to apply; to come back; to found; to explain; to form; to define; to arrange.

Nouns: computer; answer; commands; memory; element; device; information; state; aim; heart; solution; computation.

Adjectives: main; whole; separate; quick; correct; large; main (storage); following; every; following; specific; different; real.

13. Сравните и проанализируйте предложения, содержа­
щие зависимый и независимый причастные обороты.
Переведите их.

1. Having returned to the accumulator the results of arith­
metic operations are transferred to main storage. The results of
arithmetic operations are returned to the accumulator, the stor­
age register transfering them to main mamory. The results of
arithmetic operations being returned to the accumulator, the
storage register transfer them to main memory. Being returned
to the accumulator the results of arithmetic operations are trans­
ferred to main memory.

2. When passing through a conductor free electrons form an
electric current. Free electrons passing through a conductor, an
electric current is generated. Free electrons pass through a con­
ductor, an electric current being generated. Free electrons pass­
ing through a conductor form an electric current.

3 Instructions being obtained, the control unit causes other units to perform the necessary operations. Instructions are ob­tained, the control unit causes other units to perform the oper­ations. Having obtained the instructions the control unit caus­es other units to perform the operations. Obtaining the instructions the control unit causes other units to perform the operations.

4. The elements having unknown properties cannot be used for experiments. The elements have unknown properties, exper-

107_________________________ Unit 8. Central Processing Unit

iments with these elements being impossible. Having unknown properties the elements cannot be used for experiments. The elements having unknown'properties, experiments with them are impossible.

5. When moving in a material charged particles (заряженные частицы) produce magnetic properties (свойства) of this ma­terial. Charged particles moving in a material produce magnet­ic properties. Charged particles moving in a material, magnetic properties of this material are produced. Charged particles move in a material, magnetic properties of the material being pro­duced.

14. Прочтите внимательно текст и составьте к нему план в назывной форме. Прочтите текст еще раз, разверни­те пункты плана и составьте реферат на английском языке, озаглавьте текст.

*•* cjK

It is known that one of the fundamental parts of the com­puter is a control unit. This unit controls the computation pro­cess automatically, without man's participation. It sends signals to all other parts of the computer to specify what they must do. First of all, the control unit tells the main memory what data must be transferred to the arithmetic-logical unit and other de­vices. Then it enables the arithmetic-logical unit to perform the required operation. Finally, it places the obtained results in the main memory.

It is important to note that the control unit operation is de­termined by an algorithm of a problem solution. The algorithm is a sequence of arithmetic and logical operations. These oper­ations must be performed on the initial data for solving the prob­lem.

Description of an algorithm in a form acceptable by a com­puter is called a program. A program is a list of sequential com­puter instructions enabling a computer to solve a problem. In order to be acceptable by the computer instructions must be encoded into a digital form.

In conclusion it should be pointed out that the main feature of a computer is automatic control of the problem solution pro­cess. It is based on the programmed-control principle.

Английский язык. Основы компьютерной грамотности 108

15. Выполните письменный перевод текстов по вариантам. Озаглавьте тексты.

* * #

1. In 1960's advances in microelectronic components led to
the development of the minicomputer, followed more recently
by an even smaller microcomputer. Both have filled a need for
small but relatively flexible processing systems able to execute
comparatively simple computing functions at lower costs.

In 1971 Intel Corporation delivered the first microproces­sor, the 4004. All the logic to implement the central processing unit of a tiny computer was put onto a single silicon chip less than 1/4 inch square. That design was soon followed by many others. The progress toward smaller computers is continuing, designers are working at nano-computers and pico-computers.

When the central processing unit of a computer is imple­mented in a single, or very small number of integrated circuits, we call it a microprocessor. When a computer includes a mi­croprocessor as its major component, such device is called a microcomputer.

Today the hardware in data-processing machines is built out of microelectronic devices. Advances in microelectronic devices give rise to advances in data-processing machinery.

2. The computer has made it possible to mechanize much
of the information interchange and processing that constitute
the nervous system of our society.

The versatility and convenience of the microprocessor has changed the entire architecture of modern computer systems. No longer is the processing of information carried out only in the computer's central processing unit. Today there is a trend toward distributing more processing capability throughout a computer system, with various areas having small local proces­sors for handling operations in those areas.

There are a number of advantages of distributed processing. First, .since many elements of the computer can be working on different portions of the same task, the work may be done fast­er. Second, if one element in the network malfunctions, its workload can be shifted to another element or shared among several elements, so that the entire work is relatively immune

109 Unit 8. Central Processing Unit

to failure. Third, the network can be small enough to be con­tained within a single laboratory or building, or it can be spread out over a wide area.

TESTS

1. Вставьте необходимые слова вместо пропусков.

1. Programs and data to be processed must be in the____________

memory.

,a) internal; b) external; c) secondary

2. The control unit_________ instructions from the program.

a) sends; b) changes; c) obtains

3. The results of arithmetic operations are returned to the
_____ for transferring to main storage.

a) decoder; b) counter; c) accumulator

4. The instruction to be__________ in control unit is read out

from primary storage into the storage register.

a) calculated;Jb) executed; c) read out

5. The______ performs logical comparisons of the contents

of the storage register and the___________ .

a) adder; b) accumulator; c) comparer

6. The read out command is passed from the____________ regis­
ter to the________ register.

a) instruction; b) address; c) storage

7. CPU is designed to________ and to_______ basic instruc­
tions for the computer.

/a) control; b) consist; c) carry ouU

8. CU and ALU consist of electronic circuits with millions
of______ .

a) sensors; b) servers; c) switches

2. Согласуйте слова левой колонки с их интерпретацией,
предложенной справа.

1. CPU ^f/- -a) performs the processing operations;

2. CU ^ -b) carries out logical comparisons of stor-

age;

3. ALU С -с) executes basic arithmetic functions;

4. accumulator; d) coordinates the operation of the whole

system;