Before reading text 2, learn these words and phrases.
Лекции.ИНФО


Before reading text 2, learn these words and phrases.



medium (pi. media) — носитель; среда

capacity — емкость; объем (памяти); пропускная спо­собность

media capacity — емкость носителя

data access time — время доступа к данным

per bit — на единицу информации

to transfer— передавать(ся); переносить(ся); пересы­латься)

archival storage — архивное ЗУ; архивная память

to depend — зависеть от; полагаться, рассчитывать на

to rotate — вращать(ся); чередовать(ся); сменять(ся)

reason— причина; основание; довод; обосновывать; делать вывод

solid-state device — твердотельный прибор

magnetic core — магнитный сердечник

bipolar semiconductor — биполярный полупроводник

metal-oxide semiconductor (MOS) — структура металл-оксид-полупроводник

randomly — произвольно

random-access memory (RAM) — оперативное запомина­ющее устройство (ОЗУ)

sound recording — звукозапись

to arrange — размещать; располагать; устанавливать; монтировать

tape device — ЗУ на магнитной ленте

to range — классифицировать; располагать в порядке; лежать в диапазоне

magnetic disc storage — ЗУ на магнитном диске

moving-head device — устройство с двигающейся голов­кой

predominant — преобладающий; доминирующий

flexible —гибкий; настраиваемый; изменяемый

floppy (disk) — гибкий диск(ета); ЗУ на гибком диске

to meet the demands — удовлетворять потребности

 

Text 2. Storage Devices.

 

Storage media are classified as primary storage or secondary storage on the basis of combinations of cost, capacity, and access time. The cost of storage devices is expressed as the cost per bit of data stored. The most common units of cost are cents, millicents (0.001 cents) and microcents (0.000001 cents). The time required for the computer to locate and transfer data to and from a storage medium is called the access time for that medi­um. Capacities range from a few hundred bytes of primary stor­age for very small computers to many billions of bytes of archi­val storage for very large computer systems.

Memories may be classified as electronic or electromechani­cal. Electronic memories have no moving mechanical parts, and data can be transferred into and out of them at very high speeds. Electromechanical memories depend upon moving mechanical parts for their operation, such as mechanisms for rotating mag­netic tapes and disks. Their data access time is longer than is that of electronic memories; however they cost less per bit stored and have larger capacities for data storage. For these reasons most computer systems use electronic memory for primary storage and electromechanical memory for secondary storage.

Primary storage has the least capacity and is the most expen­sive; however, it has the fastest access time. The principal pri­mary storage circuit elements are solid-state devices: magnetic cores and semiconductors. For many years magnetic cores were the principal elements used in digital computers for primary storage. The two principal types of semiconductors used for memory are bipolar and metal-oxide semiconductors (MOS). The former is faster, the latter is more commonly used at present. Because data can be accessed randomly, semiconduc­tor memories are referred to as random-access memory, or RAM.

There is a wide range of secondary storage devices. Typical hardware devices are rotating electromechanical devices. Mag­netic tapes, disks, and drums are the secondary storage hardware most often used in computer systems for sequential processing. Magnetic tape, which was invented by the Germans during World War II for sound recording, is the oldest secondary stor­age medium in common use. Data are recorded in the form of small magnetized "dots" that can be arranged to represent coded patterns of bits.

Tape devices range from large-capacity, high-data-rate units used with large data processing systems to cassettes and cartridges used with small systems. Magnetic disk storage, introduced in the early 1960s, has replaced magnetic tape as the main meth­od of secondary storage. As contrasted with magnetic tapes, magnetic discs can perform both sequential and random pro­cessing. They are classified as moving-head, fixed-head, or com­bination moving-head and fixed-head devices. Magnetic discs are the predominant secondary storage media. They include flexible, or floppy discs, called diskettes. The "floppies" were introduced by IBM in 1972 and are still a popular storage me­dium to meet the demands of the microcomputer market.

Exercise 1. Find the word combinations in the text.

Запоминающие устройства; носители памяти; первич­ные ЗУ; вторичные ЗУ; время доступа; стоимость ЗУ; диа­пазон емкости памяти; архивная память; движущиеся ме­ханические части; вращающиеся магнитные ленты и диски; по этим причинам; твердотельные устройства; маг­нитные сердечники; полупроводники; оперативное ЗУ; аппаратное обеспечение вторичной памяти; звукозапись; намагниченные точки; представлять зашифрованную ком­бинацию единиц информации; в отличие от магнитных лент; последовательная и произвольная обработка; устрой­ства с движущейся и фиксированной головкой; удовлет­ворять потребности; гибкий диск.

Exercise 2.Answer the questions on the text.

1. How are storage media classified?

2. How is the cost of storage devices expressed?

3. What is the access time for stor­age media?

4. How does the storage capacity range?

5. What are the two main types of storage devices?

6. What are electronic storage devices?

7. What are the principal primary storage cir­cuit elements?

8. What are the main secondary storage devic­es?

9. What is the oldest secondary medium and when was it invented?

10. What is a floppy?

Exercise 3. Translate the sentences with he Participle 1 and Participle 2 into Russian.

1. Electromechanical memories depend upon moving me­chanical parts for their operation. 2. The time required for the computer to locate and transfer data to and from a storage me­dium is called the access time. 3. Being not visible software makes possible the effective operation of computer system. 4. Having invented magnetic tapes the Germans used them as the secondary storage medium. 5. When properly programmed computers don't make computational errors. 6. Having been in­troduced in the early 1960s magnetic disc storage has replaced magnetic tape storage. 7. The control unit interpreting instruc­tions is one of the important parts of any computer system. 8. Data recorded in the form of magnetized'dots can be arranged to represent coded patterns of bits. 9. As contrasted with mag­netic tapes magnetic discs can perform both sequential and ran­dom processing. 10. While having no moving mechanical parts electronic memories can transfer data at very high speed

.

Text 3. Memory

 

Itis interesting to note that memory, one of the basic com­ponents of the computer, is often called storage. It stores cal­culation program, the calculation formulae, initial data, inter­mediate and final results. Therefore, the functions of the computer memory may be classified in the following way. Firstly, the computer memory must store the information transmitted from the input and other devices. Secondly, memory should produce the information needed for the computation process to all other devices of the computer.

Generally, memory consists of two main parts called the main, primary or internal, memory and the secondary, or ex­ternal memory. The advantage of the primary memory is an extremely high speed. The secondary memory has a compara­tively low speed, but it is capable of storing far greater amount of information than the main memory. The primary storage takes a direct part in the computational process. The second­ary storage provides the information necessary for a single step in the sequence of computation steps.

The most important performance characteristics of a stor­age unit are speed, capacity and reliability. Its speed is measured in cycle time. Its capacity is measured by the number of ma­chine words or binary digits. Its reliability is measured by the number of failures (отказ) per unit of time.

 

Exercise 1. Find in the text the following words and phrases.

Основной компонент, программа вычисления, исходные данные, промежуточные результаты, поступать (передавать), производить информацию, вычислительный процесс, внутренняя память, внешняя память, преимущество, очень высокая скорость, сравнительно, бОльшее количество информации, принимать прямое участие, последовательность вычисления, рабочие характеристики, скорость, вместимость, надежность, время цикла, двоичный знак, количество отказов.

Exercise 2. Find in the sentences Participle 1 or Participle 2. Detect their function.

  1. Itis interesting to note that memory, one of the basic com­ponents of the computer, is often called storage.
  2. Its speed is measured in cycle time.
  3. Therefore, the functions of the computer memory may be classified in the following way.
  4. The secondary memory has a compara­tively low speed, but it is capable of storing far greater amount of information than the main memory.
  5. Memory should produce the information needed for the computation process to all other devices of the computer.
  6. Memory consists of two main parts called the main, primary or internal, memory and the secondary, or ex­ternal memory.
  7. The functions of the computer memory may be classified in the following way.

Exercise 3. Answer the questions on the text.

1. What is memory?

2. What is the function of memory?

3. What are the main parts of memory?

4. What are advantages and disadvantages of a storage unit?

5. What are their functions?

6. What are performance characteristics of the main and-secondary memory?

7. What units are performance characteristics measured by?

Exercise 4. Give a summary of the text in 5-6 sentences. Use the words and phrases:

Basic component, storage, the function of…, to store, to produce, two main parts, primary storage, secondary storage, performance characteristics.

 









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