C Units of memory

The electronic circuits in computers detect the difference between two states: ON (the current passes through) or OFF (the current doesn’t); they represent these states as 1 or 0. Each 1 or 0 is called a binary digit or bit.

Bits are grouped into eight-digit codes that typically represent characters (letters, numbers and symbols). Eight bits together are called a byte. For example, 01000001 is used for the character A. Computers use a standard code called ASCII for the binary representation of characters.

In order to avoid complex calculations of bytes, we use bigger units. A kilobyte (KB) is 1,024 bytes; a megabyte(MB) is 1,024 kilobytes; a gigabyte (GB) is 1,024 megabytes; a terabyte (TB) is 1,024 gigabytes. We use these units to describe the RAM memory, the operating capacity of disks and the size of a program or document.

Exercises

Look at A opposite. Then match the sentence beginning (1-6) with the correct endings (a-f).

1. The CPU processes data and

2. The control unit is the part of the CPU that

3. The arithmetic and logic unit is able to make

4. The registers are high-speed storage

5. Data contained in RAM is lost when

6. ROM memory can only be read:

a areas within the CPU.

byou can’t make changes to it.

c controls the way instructions are executed.

dthe computer is turned off.

e coordinates the other parts of the computer.

fcalculations: add, subtract, multiply and divide.

Solve the clues and complete the puzzle with words from the opposite page.

1. Intel …… are used in many computers.

2. Each 0 or 1 is called a bit, short for … digit.

3. Special cards can be inserted into expansion … .

4. A … controls the timing within the PC by sending signals to synchronize its circuits and operations.

5. The processor speed is measured in … .

6. … carry signals between different parts of a PC.

7. … cards improve the computer’s performance.

8. The … uses ROM to control the input/output of data.

9. The main printed circuit board is called the … .

Down: The brain of a computer

8.3 Read this product description and answer the questions below.

Processor and memory:

- Intel Core 2 Duo processor at 2.4 GHz

- 533 MHz Front Side Bus

- 1,024 MB of RAM; can be expanded up to 4 GB

- 200 GB Hard disk

- Double Layer DVD +/-R/RW drive

- Microsoft Windows

1. How fast is the CPU?

2. Which term is used to describe the CPU data bus?

3. How much RAM does the computer have?

4. Can you add extra RAM chips? How many?

UNIT 9 Disks and drives