Basic English for Computing / Basic English for Computing (Units) / UNIT 22
.doc22 Low-level systems
Tuning-in
Task 1 Label this diagram of a computer system with these terms.
Task 2 Work in pairs. What other examples of input devices, output devices, and storage devices can you add to the diagram?
Listening: The CPU
Task 3 Study this diagram of the Central Processing Unit. Answer these questions.
1 What does ALU mean?
2 What is a register?
3 What does the control unit do?
Task 4 Listen to Part 1 of the recording. Check your answers to Task 3.
Task 5 Listen again to find the answers to these questions.
1 What sort of functions does the ALU perform?
2 Name a logic operation performed by the ALU.
3 Which part of the CPU controls printers?
4 What is the difference between registers and main memory?
Task 6 Look at the diagram in Task 3 again. Try to answer these questions.
1 What is the function of buses?
2 Which buses are bidirectional?
3 What kind of information is carried by the data bus?
4 What does unidirectional mean?
Task 7 Listen to Part 2 of the recording. Check your answers to Task 6. Then complete this table.
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Uni/Bidirectional |
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Data |
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Address |
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Control |
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Reading:The machine cycle
Task 8 Study this diagram of the machine cycle. Answer these questions.
1 How many steps are there in the machine cycle?
2 What are the Fetch and Decode steps together called?
3 Which steps together are called E-time?
4 Where does the Decode step happen?
Task 9 Read this text quickly to check your answers to Task 8.
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How the CPU executes program instructions Let us examine the way the central processing unit, in association with memory, executes a computer program. Many personal computers can execute instructions in less than one-millionth of a second, whereas supercomputers can execute instructions in less than one-billionth of a second. Before an instruction can be executed, program instructions and data must be placed into memory from an input device or a secondary storage device.The data will probably make a temporary stop in a register. As Figure 1 shows, once the necessary data and instruction are in memory, the central processing unit performs the following four steps for each instruction: 1 The control unit fetches (gets) the instruction from memory. 2 The control unit decodes the instruction (decides what it means) and directs that the necessary data be moved from memory to the arithmetic/logic unit.These first two steps together are called instruction time, or l-time. 3 The arithmetic/logic unit executes the arithmetic or logical instruction.That is, the ALU is given control and performs the actual operation on the data. 4 The arithmetic/logic unit stores the result of this operation in memory or in a register. Steps 3 and 4 together are called execution time, or E-f/me.The control unit eventually directs memory to release the result to an output device or a secondary storage device.The combination of l-time and E-time is called the machine cycle. |
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Task 10 Read the text again to find the answers to these questions.
1 What must be put into memory before an instruction can be executed?
2 Where will the data be stored temporarily?
3 What operation does the control unit perform on the data?
4 Where does the ALU store the results of its operations?
5 What happens to the results eventually?
6 What is the machine cycle?
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Language work: Contrast |
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Study these pairs of statements. |
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1 The data bus is bidirectional. The address bus is unidirectional. 2 Registers hold data immediately required. Main memory stores data required in the near future. 3 PCs can process in a millionth of a second. Supercomputers can process in a billionth of a second. |
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Each pair contains a contrast. We can show this by linking them as follows: |
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1 The data bus is bidirectional, whereas the address bus is unidirectional. 2 Registers hold data immediately required. In contrast, main memory stores data required in the near future. 3 PCs can process in a millionth of a second, but supercomputers can process in a billionth of a second. |
Task 11 Link each of these pairs of contrasting statements using whereas, in contrast, or but.
1 Dot matrix printers are noisy. Laser printers are quiet.
2 Floppy disks store small amounts of data. Hard disks store large amounts of data.
3 Handheld computers fit into your pocket. Supercomputers occupy a whole room.
4 High-level languages are easy to understand. Machine code is very difficult to understand.
5 Basic is a simple language. С++ is complex.
6 Modern computers are powerful and relatively cheap. Older computers were less powerful and quite expensive.
7 An analyst analyses problems and finds solutions. A programmer turns these solutions into computer programs.
8 A graphics package produces images and designs. A word processor produces texts.
Problem-solving
Task 12 Work in pairs, A and B. Explain to your partner how to convert a number
from one system to another. You can write down the steps and show them to your partner, but you must explain each step in English.
Student A Your conversion is on page 118.
Student В Your conversion is on page 119.
Writing
Task 13 Describe how an interrupt works by linking these pairs of sentences using suitable time words.
1 A printer runs out of paper.
An interrupt carries a signal to the CPU.
2 The CPU receives the signal.
The CPU interrupts its tasks.
3 The CPU saves its current status in a special area of memory.
The CPU sends a message to the user.
4 The user reloads the paper tray.
The processor returns to its previous state.