Some features of a digital computer

Itshould be noticed that even in a large-scale digital system, such as in a computer, or in a data-processing, control or digital-communication system, there are only a few basic operations which must be performed. These operations may be operated many times. The four circuits most commonly employed in such systems are known as the OR, AND, NOT and FLIP-FLOP. They are called logic gates or circuits.

An electronic digital computer is a system which processes and stores very large amount of data and which solves scientific problems of numerical computations of such complexity and with such speed that solution by human calculation is not feasible. So the computer as a system can perform numerical computations and follow instructions with extreme speed but it cannot program itself.

We know that the numbers and the instructions which form the program, the computer is to follow; are stored in an essential part of the computer called the memory. The second important unit of the computer is the control whose function is to interpret orders. The control must convert the command into an appropriate set of voltages to operate switches and carry out the instructions conveyed by the order. The third basic element of a computer is the arithmetic device, which contains the circuits performing the arithmetic computations: addition, subtraction, etc. The control and arithmetic components are called the central processor. Finally a computer requires appropriate input-output devices for inserting numbers and orders into the memory and for reading the final result.

Suppose a command to perform an addition or division has been transmitted to the central processor. In response to this order the control must select the correct operands from the memory, transmit them to the arithmetic unit and return to the memory the result of the computation. The memory serves for storing not only the original input data, but also the partial results which will have to be used again as the computation proceeds.

Lastly, if the computation doesn't stop with the execution of this instruction and the storage of the partial result, the control unit must automatically pass on to the next instruction. The connection of the control unit back to the input permits insertion of more data when there is room in the memory.

 

Задание 3 Ответьте на вопросы, используя информацию текста

 

1. What are the most commonly used circuits in any computer? 2. How are they called? 3. What kind of a system is a digital computer? 4. Is there anything that a computer cannot do itself? What is it? 5. Where are the instructions and digits stored? 6. What is the function of the control? 7. What does the arithmetic device serve for? 8. What components form the central processor? 9. What other devices in addition to the above-mentioned ones does a computer require? 10. How are computations performed in a computer?

 

Задание 4 Найдите в тексте английские эквиваленты следующих сочетаний:

 

Крупномасштабная цифровая система; система обработки данных; система цифровой связи; наиболее широко распространенные схемы; логические схемы; решать научные проблемы; выполнять числовые вычисления; интерпретировать команды; приводить в действие переключатели; выполнять команды; нуждаться (требовать) в необходимом устройстве ввода-вывода; введение чисел и команд; считывание конечных результатов; передавать команду в центральный процессор; в ответ на; хранение частичных результатов; позволить введение новых данных; свободное место в памяти.

 

Задание 5 Согласуйте слова в левой колонке с их интерпретацией, предложенной справа.

 

1. Functional organization of a computer	a) processes and stores large amount of data and solves problems of numerical computations;
2. Input	b) circuits used in large-scale digital systems;
3. Memory	c) method of interrelation of the main units of a computer;
4. Control unit	d) removing data from the device to the outside world;
5. Output	e) inserting information into the computer;
6. Arithmetic unit	f) a code of combinations of electric pulses;
7. Machine language	g) performs addition, subtraction, multiplication, etc;
8. Logic gates	h) stores original data as well as partial results;
9. Digital computer	i) causes all parts of the computer to act as a team.

 

Тексты 3,4. Logical circuit elements, The definition of mechanical brain

 

Задание 1 Составьте вопросы к текстам:

 

Logical circuit elements

As it is known, any digital calculation — whether it is performed by 'pencil and paper' methods or with the aid of an automatic computer — must first be broken down into a sequence of elementary arithmetical operations, such as addition, or multiplication. Each such arithmetical operation may be converted into a sequence of simple logical operations. It should be noted that a binary digit may take only two values — "zero" and "one". A logical proposition may be either true or false.

A symbolism and a set of rules suitable for manipulating 'yes or no' logical propositions was developed by George Boole, a self-educated genius who became Professor of Mathematics at Cork University in the middle of the 19^th century. The techniques of Boolean algebra are now extensively used by electrical engineers for the design and analysis of switching circuits. Both the arithmetic and control units of a computer consist of sets of switching circuits for directing and manipulating electrical pulse signals.

The process of combining a number of electronic circuits of known logical properties into an integrated system capable of performing special arithmetical or control functions is known as logical design.