B) Прочитайте текст и выпишите термины. Объясните выделенные слова и словосочетания: Units of Memory

Bit – basic unit of memory

Information is processed and stored in computers as electrical signals. A computer contains thousands of electrical circuits connected by switches that can only be in one of two possible states: ON (the current is flowing through the wire) or OFF(the current is not flowing through the wire). To represent these two conditions we use binary notation in which 1 means ON and 0 means OFF. This is the only way a computer can ‘understand’ anything. Everything about computers is based upon this binary process. Each 1 or 0 is called a binary digit, or bit.

Bytes and characters

1s and 0s are grouped into eight-digit codes that typically represent characters (letters, numbers and symbols). Eight bits together are called a byte. Thus, each character in a keyboard has its own arrangement of eight bits. For example, 0100001 for A, 01000010 for B and 01000011 for C.

The ASCII code

The majority of computers use standard system for the binary representation of characters. This is the American Standard Code for Information Interchange, known popularly as ‘ASCII’ (pronounced as ‘ask key’). There are 256 different ways of combining 0 and 1 bits in a byte. So they can give us 256 different signals. However, the ASCII code only uses 128 bytes to represent characters. The rest of the bytes are used for other purposes.

The first 32 codes are reserved for characters such as the Return key, Tab, Escape, etc. Each letter of the alphabet and many symbols (such as punctuation marks), as well as the ten numbers have ASCII representations. What makes this system powerful is that these codes are standard.

Kilobytes, megabytes and gigabytes

In order to avoid astronomical figures and sums in the calculation of bytes we use units such as kilobytes, megabytes and gigabytes. One kilobyte is 1,024 bytes (2¹⁰) and it is represented as KB, or more informally K. One megabyte is equivalent to 1,024 kilobytes and one gigabyte is 1,024 megabytes.

We use these units (KB, MB, GB) to describe the RAM memory, the storage capacity of disks and the size of any application or document. For instance, the text of the book contains roughly 1 MB of information.

(E.C.U.)

У пражнение 24. Прослушайте текст и укажите, упомянуты ли данные идеи в тексте (+/-):

Primary and Secondary Memory

1. The term ‘memory’ can be expressed in other ways.

2. Computers are often advertised according to their memory capacity.

3. The CPU can easily access information from internal storage.

4. Minicomputers and microcomputers have a similar memory capacity.

5. The control unit needs to know the location where information is stored or needs to be stored.

6. Primary memory is more expensive than secondary memory.

7. There are two types of secondary memory devices.

8. Information stored on magnetic disk can be retrieved faster than if that same information were on tape.

9. Disks and tapes can be stored in a library.

10. Computers can process information even if complete programs are not put in internal storage.

Упражнение 25. Словам из левой колонки подберите соответствующие слова и выражения из правой колонки:

internal storage, real storage, random access, addresses, contents, sequential access, virtual storage,

means any part of memory can be read equally quickly, the information contained in the storage locations, are storage locations in internal storage, refers to memory, hooking up secondary memory devices onto memory to increase their capacity, sometimes called primary memory, information must be read from secondary memory devices in a fixed pattern.

Упражнение 26. Прочитайте текст и заполните пропуски данными ниже выражениями:

• All the information stored in the RAM is temporary

• Microcomputers make use of two types of memory

• ROM chips have ‘constant’ information

• the size of RAM is very important