There are different types of computer of varying size and power, including the following:
Supercomputer (the most powerful type of mainframe)
Mainframe (large, very powerful, multi-user i.e. can be used by many people at the same time, multi-tasking i.e. can run many programs and process different sets of data at the same time)
Minicomputer (smaller than a mainframe, powerful, multi-user, multi-tasking)
Personal computer (PC) (single user)
Desktop computer (suitable size for sitting on an office desk)
Workstation (most powerful type of desktop, used for graphic design, etc.)
Portable (can be carried around, can operate with batteries)
Laptop (large portable, can be rested on user's lap)
Notebook (size of a sheet of notebook paper)
Handheld (can be held in one hand)
Pen-based (main input device is an electronic pen)
PDA (personal digital assistant, has functions such as task lists, diary, address book)
Note that the term PC usually refers to an IBM compatible personal computer i.e. an Apple Mac personal computer is not referred to as a PC. A computer that provides a service on a network e.g. storing files, sharing a printer, is known as a server computer. Server computers usually have a UPS (uninterruptible power supply) attached to them. This is a battery that automatically provides an electricity supply to allow the server to shut itself down properly if the main supply fails.
The processor e.g. Pentium, is the most important part of the computer. It processes the data and controls the computer. Powerful computers used as servers often have more than one processor. There are two main types of memory:
a) RAM (random access memory) holds the program instructions and the data that is being used by the processor,
b) ROM (read only memory) holds the program instructions and settings required to start up the computer.
The combination of the processor and memory is sometimes referred to as the CPU (central processing unit), although sometimes the processor itself is referred to as the CPU. The other parts connected to the CPU are known as peripherals. These can include input devices, output devices, storage devices and communications devices. Input devices include: keyboards, scanners, barcode readers, digital cameras, microphones and video cameras e.g. webcams (small digital video cameras used on the Web). Output devices include: monitors (VDU display screens), printers, plotters, loudspeakers, headphones. Storage devices include: magnetic tape, floppy disks (diskettes), hard disks, CD-ROMs, CD-R disks, CD-RW disks, DVDs and MO disks. A common communications device is a modem (a modulator/demodulator used for converting digital signals to analogue signals and vice versa to allow a computer to be connected to the ordinary telephone system).
A set of connectors used for carrying signals between the different parts of a computer is known as a bus. Data is transferred constantly between the processor and memory along the system bus. Each part of memory has its own memory address and the processor determines where processed data is stored by sending an address signal along an address bus and data along a data bus. This is synchronised by an electronic clock in the CPU that determines the operating speed of the processor. Transferring data between the processor and RAM can slow up the computer; therefore, some very expensive, extremely fast memory is usually used as a cache to hold the most frequently used data.
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In a desktop computer, the CPU (central processing unit) and storage devices (pieces of equipment used for reading from and writing to a storage medium) are normally built inside a system unit which consists of a metal chassis enclosed in a flat desktop or a tower shaped case. Other peripherals are attached to the system unit by cables. Each peripheral uses its own driver card or controller (an expansion card that is plugged into special expansion slots in the system unit). Expansion cards contain the electronics required to communicate with and control the device e.g. video or graphics cards are used for monitors, soundcards are used for audio input/output and NICs (network interface cards) are used for connecting to other computers in a network. Extra memory can also be added to the computer using special memory expansion slots inside the computer. A portable computer that does not have enough space inside to fit expansion cards may use an external device called a port replicator to provide connections for peripherals.
Storage devices in the form of a disk or tape are used to store the programs and data that are not being used. Before a program or data can be used, it must be transferred from the storage device to the main RAM memory. Hard disks consist of a set of magnetic coated metal disks that are vacuum-sealed inside a case to keep out the dust. The magnetic surfaces of the disks are formatted using a read/write head to provide magnetic storage areas. These storage areas form concentric circles called tracks and each track is subdivided into sections called sectors.
The disks are rotated at high speed and read from or written to by the read/write head that moves across the surface of the disks. In server computers, hard disks can be connected together and made to operate as one unit using RAID (a redundant array of inexpensive disks). This can speed up the system and provide a way of recovering data if the system crashes (fails suddenly and completely, usually referring to the failure of a hard disk). There is a variety of optical storage devices that use laser light to read or write to a disk, including: CD-ROMs (compact disk read only memory), CD-R (recordable compact disk), CD-RW (rewritable compact disk), DVD (digital versatile disk - previously known as digital video disk).
An input device called a barcode reader is a special type of scanner for reading barcodes (a set of printed bars of varying thickness that are used to identify a product e.g. used to price items in supermarkets).
When comparing computers, the power of the computer is important. This is mainly determined by the speed and capacity (size) of each part of the computer.
Speed is measured in hertz (Hz) i.e. cycles per second.
Capacity is measured in bytes (B) where 1 byte = 8 bits (binary digits) = 1 character.
Task 2. Answer the following questions.
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1. What types of computers varying in size and power do you know? 2. Can we speak about a computer revolution with the invention of personal computers? Why? 3. What is the most important part of a computer? 4. What is referred to as the CPU? 5. Give five examples of input devices (five examples of output devices). 6. How are signals carried to different parts of a computer? 7. Where can you find the CPU and storage devices in a desktop computer? 8. What external device may a portable computer use? 9. What is the function of storage? 10. What is a hard disk? 11. How does a hard disk function? 12. Where is a barcode reader used? 13. In what storage devices is laser light used? 14. What factors are to be taken into account when buying a computer?
Task 3. Find the English equivalents for the following Russian word combination.
1. '; 2. ; 3. ; 4. ' ; 5. ; 6. ; 7. '; 8. '; 9. ; 10. '
Task 4. Match each item in Column A with its function in Column B.
| A Item | B Function |
| 1. RAM 2. processor 3. mouse 4. clock 5. 3.5// floppy drive 6. monitor 7. keyboard 8. DVD-ROM drive 9. cache 10. ROM | a. controls the cursor b. inputs data through keys like a typewriter c. displays the output from a computer on a screen d. reads DVD-ROMs e. reads and writes to removable magnetic disks f. holds instructions which are needed to start up the computer g. holds data read or written to it by the processor h. provides extremely fast access for sections of a program and its data i. controls the timing of signals in the computer j. controls all the operations in a computer |
Task 5. Mark the following as True or False.
1. The function of a hard disk drive is to delete all the files stored on a disk. 2. Swipe cards are used to provide a secure means of identifying authorised users of many different facilities such as banks, libraries, and computer labs. 3. A supercomputer is used for processing small amounts of data. 4. Barcodes provide computer readable information on a product so that it can be identified and priced automatically. 5. A cache holds the program instructions and settings required to start up the computer. 6. The capacity of memory is determined by the period of the time required for the signals to travel the distance from the memory to the arithmetic/logic unit. 7. A mainframe computer is designed to be used on an office desk and to be operated by a single user.
Task 6. Complete each sentence choosing the correct preposition from the box.
| outside, between, into, in, from, to, from, along, into, from, inside, into, across, to, from, to, into |
1. The CPU is a large chip......... the computer. 2. Data always flows......... the CPU......... the address bus. 3. The CPU can be divided......... three parts. 4. Data flows......... the CPU and the memory. 5. Peripherals are devices......... the computer but linked......... it. 6. The signal moves......... the VDU screen......... one side......... the other. 7. The CPU puts the address......... the address bus. 8. The CPU can fetch data......... memory......... the data bus. 9. A program is read......... disk.......... memory. 10. The hard disk drive is......... a sealed case. 11. Tracks are divided......... sectors.
Task 7. Give the appropriate translation to the Ukrainian words.
1. There are also in the office, at home, and at school. 2. Twenty or thirty years ago, most books on computers , , because they were the most common. 3. The basic parts of for the home are . 4. All of these disk platters inside the sealed case but each disk has its own . 5. are a form of that can be inserted into a computers . 6. Typically, , using the same practiced in primary coding. 7. constituted another in the growth of computer technology. 8. The method of as well as define computer generations. 9. г and convenience of the microprocessor has altered of modern computer systems. 10. The speed of modern computers is the speed of .
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Task 8. Translate the following sentences into English.
1. ' , , . 2. , ' , ' . 3. ' , , , . 4. ' ' . 5. PC- ' , , . 6. ' . 7. (platter) , - 䳺 .
Task. 9. Find the answers to these questions in the following texts.
1. What is one of the main causes of a PC not running at its highest potential speed?
2. What word in the text is used instead of buffer?
3. What device looks after cache coherency?
4. What is the main alternative to write-through cache?
5. When does a write-back cache write its contents back to main memory?
6. When is data marked as dirty in a write-back cache?
7. What determines what data is replaced in a disk cache?
Text 2B. CACHE MEMORY
Most PCs are held back not by the speed of their main processor, but by the time it takes to move data in and out of memory. One of the most important techniques for getting around this bottleneck is the memory cache.
The idea is to use a small number of very fast memory chips as a buffer or cache between main memory and the processor. Whenever the processor needs to read data it looks in this cache area first. If it finds the data in the cache then this counts as a cache hit and the processor need not go through the more laborious process of reading data from the main memory. Only if the data is not in the cache does it need to access main memory, but in the process it copies whatever it finds into the cache so that it is there ready for the next time it is needed. The whole process is controlled by a group of logic circuits called the cache controller.
One of the cache controllers main jobs is to look after cache coherency which means ensuring that any changes written to main memory are reflected within the cache and vice versa. There are several techniques for achieving this, the most obvious being for the processor to write directly to both the cache and main memory at the same time. This is known as a write-through cache and is the safest solution, but also the slowest.
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The main alternative is the write-back cache which allows the processor to write changes only to the cache and not to main memory. Cache entries that have changed are flagged as dirty, telling the cache controller to write their contents back to main memory before using the space to cache new data. A write-back cache speeds up the write process, but does require a more intelligent cache controller.
Most cache controllers move a line of data rather than just a single item each time they need to transfer data between main memory and the cache. This tends to improve the chance of a cache hit as most programs spend their time stepping through instructions stored sequentially in memory, rather than jumping about from one area to another. The amount of data transferred each time is known as the line size.
If there is a cache hit then the processor only needs to access the cache. If there is a miss then it needs to both fetch data from main memory and update the cache, which takes longer. With a standard write-through cache, data has to be written both to main memory and to the cache. With a write-back cache the processor needs only write to the cache, leaving the cache controller to write data back to main memory later on.
HOW A DISK CACHE WORKS
Disk caching works in essentially the same way whether you have a cache on your disk controller or you are using a software-based solution. The CPU requests specific data from the cache. In some cases, the information will already be there and the request can be met without accessing the hard disk.
If the requested information isnt in the cache, the data is read from the disk along with a large chunk of adjacent information. The cache then makes room for the new data by replacing old. Depending on the algorithm that is being applied, this may be the information that has been in the cache the longest or the information that is the least recently used.
The CPUs request can then be met, and the cache already has the adjacent data loaded in anticipation of that information being requested next.
Task 10. Match the terms in Table A with the statements in Table B.
| Table A | Table B |
| 1. cache hit 2. cache controller 3. cache coherency 4. write-through cache 5. write-back cache 6. line size | a The process of writing changes only to the cache and not to main memory unless the space is used to cache new data b The amount of data transferred to the cache at any one time c The process of writing directly to both the cache and main memory at the same time d The processor is successful in finding the data in the cache e Ensuring that any changes written to main memory are reflected within the cache and vice versa f The logic circuits used to control the cache process |
Task 11. Mark the following as True or False:
1. Cache memory is faster than RAM.
2. The processor looks for data in the main memory first.
3. Write-through cache is faster than write-back cache.
4. Write-back cache requires a more intelligent cache controller.
5. Most programs use instructions that are stored in sequence in memory.
6. Most cache controllers transfer one item of data at a time.
7. Hardware and software disk caches work in much the same way.
GRAMMAR REVIEW.
PAST FORMS
| Past Simple | Past Continuous | Past Perfect | Past Perfect Continuous | |
| When | yesterday, two days ago, last week | at 5 p.m., at noon, from 2 p.m. to 4 p.m., when he entered | by 5 oclock | for two hours, for three months, for a long time |
| Affirmatie sentence | I/she/he/it/we/you/they played/wrote | I was playing She/he/it was playing You/we/they were playing | I/she/he/it/you/we /they had played/written | I/she/he/it/you/we/they had been playing/writing |
| Negative sentence | I/she/he/it/we/you/they did not play/write | I was not playing She/he/it was not playing They/you/we were not playing | I/she/he/it/you/we /they had not played/written | I/she/he/it/you/we /they had not been playing / writing |
| General question | Did I/she/he/it/we/you/they play /write? | Was I playing? Was she/he/it playing? Were you/we/they playing? | Had I/she/he/it/you/we /they played/written? | Had I/she/he/it/you/we/they been playing/writing? |
| Wh-question | What did I/she/he/it/we/you/they play/write? | What was I playing? What was he/she/it playing? What were they/you we playing? | What had I/she/he/it/you/we /they played/written? | What had I/she/he/it/you/we/they been playing/writing? |
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| Adverbs of frequency (Signal Words) |
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