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Stáhnout celý tento materiálVB035 English I
UNIT 1 Computer Users
INTRODUCTION
A computer is a device that processes data according to a set of instructions known as a program.
The equipment is known as the hardware and the programs and data are the software. A special set of
programs, called an operating system, provides an interface for the user and allows applications
programs to communicate with the hardware. Common applications programs include
wordprocessors for creating and editing texts, spreadsheets for calculating mathematical formulae
and databases for storing data in a way that allows the data to be sorted and searched. Anti-virus
programs are used to detect and remove viruses (harmful programs that can reproduce themselves
and attach themselves to other programs). Some operating systems have graphical (user) interfaces
that allow the computer user to select items from menus (lists of choices) and to start programs using
an input device called a mouse. This is done by pressing a button on the mouse i.e. clicking the
mouse. The main device for inputting the data is a typewriter-style keyboard and the output is
commonly displayed on a monitor screen that looks like a small television screen.
There is a range of sizes and types of computer. Those designed for use by one person at a time are
known as personal computers (PCs) although the term PC is usually only applied to personal
computers that are compatible with the standards laid down by the company known as IBM
(International Business Machines). Personal computers include desktop computers (for use on an office
desk) and handheld computers that can be carried around by the user. Electronics can be added to
desktop computers by plugging in expansion cards (electronic circuit boards that can be plugged into
special sockets called expansion slots).
It is also possible to build all the main parts of a computer into one electronic integrated circuit
packaged as a single electronic chip (the common name for a microchip; an electronic integrated circuit
in a small package) i.e. the 'computer on a chip'. This enables computers to be built into other devices
including household devices such as washing machines and fridges and to be incorporated into plastic
cards i.e. smart cards, which are able to store information such as health records, drivers' licences,
bank balances, etc. Devices that include a computer circuit are commonly referred to as smart devices.
A multimedia computer can process different forms of data including text, graphics, audio (sound),
animation and video. This enables computer systems to be used for a combination of education and
entertainment, sometimes referred to as edutainment.
Unlike most machines, computers do not have a fixed purpose. They are multi-purpose tools. They
can be used in a very wide variety of situations and are found in a wide range of systems including
security systems, cars and phones. Advanced systems, known as expert systems, enable computers to
'think' like experts. Medical expert systems, for example, can help doctors diagnose an illness and
decide on the best treatment. As computer systems are developed, they are becoming more common
and are gradually being used for more and more purposes. How they are developed, and for what
purposes they are actually used in the future, can be influenced by computer users. A variety of
devices known as peripherals can be added externally to a computer. One of the most common
peripherals is a printer used for printing the computer output (the processed data or signals that come
out of a computer system) on paper. A digital camera allows photographs to be input to a computer for
editing.
Not all computer systems are compatible i.e. they cannot use the same programs and data.
Connecting computers together to form a network can provide the 'connectivity' required to enable
computers and software to communicate and to share resources. Networks connected together form
an internet. The connection of networks throughout the world is known as the Internet (note that a
capital I is used) or, more simply, the Net. Various communication services are available on the Internet,
including email (electronic mail) for sending and receiving text messages and IRC (Internet Relay Chat)
which allows users to communicate using text messages in real-time i.e. without any delay, while the
users are logged on (connected to a network system account, normally using a password) to the
system. An Internet service called FTP (File Transfer Protocol) is used for transferring data or program
files between the powerful server computers that provide the network services and the client computers
that use these services e.g. downloading music files. Note that copying data from a larger server system
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to a client is referred to as downloading and copying from the client to the server is known as
uploading.
One of the newest and most popular services available on the Internet is the World Wide Web
(WWW) which is often simply referred to as the Web (note the use of the capital W). The Web contains
interlinked documents called webpages. A set of related webpages stored together on a server
computer is called a website. Websites, such as Dogpile and Askjeeves, give the user access to
special programs called search engines that are designed to allow the user to find relevant webpages
on the Web. An Internet system designed to provide free, interactive access to vast resources for
people all over the world is sometimes referred to as an information superhighway.
Services such as these allow people to telecommute (use their computers to stay in touch with the
office while they are working at home). Computer uses mentioned in this unit include producing
greetings cards; learning, using three-dimensional graphics programs called 'Splat the Cat' and 'Pets 3';
using the Microsoft Word wordprocessing program including features such as clipart (ready-drawn
graphic images that can be inserted into documents); communicating on the Internet using email and
chat programs including the use of email attachments (other types of files e.g. video files attached to
simple email text messages); distance learning and videoconferencing (a form of communication over
a network that uses video cameras so that the people taking part can see and hear each other);
electronic classrooms or boardrooms; browsing the Web (moving from webpage to webpage using a
Web browser program); selling, using a website; painting; scanning pictures; downloading music and
creating CD-ROMs (compact disk read only memory, commonly referred to as CDs). CD-ROMs are
storage devices that use laser light for reading and writing data. The most common storage device is a
hard disk (a set of aluminium disks coated in a magnetic material and enclosed in a vacuum-sealed
case) used for storing the operating system and applications programs as well as the user's data.
SPECIALIZED READING
Computers Make the World Smaller and Smarter
The ability of tiny computing devices to control complex operations has transformed the way many
tasks are performed, ranging from scientific research to producing consumer products. Tiny 'computers
on a chip' are used in medical equipment, home appliances, cars and toys. Workers use handheld
computing devices to collect data at a customer site, to generate forms, to control inventory, and to
serve as desktop organisers.
Not only is computing equipment getting smaller, it is getting more sophisticated. Computers are part
of many machines and devices that once required continual human supervision and control. Today,
computers in security systems result in safer environments, computers in cars improve energy
efficiency, and computers in phones provide features such as call forwarding, call monitoring, and call
answering.
These smart machines are designed to take over some of the basic tasks previously performed by
people; by so doing, they make life a little easier and a little more pleasant. Smart cards store vital
information such as health records, drivers' licenses, bank balances, and so on. Smart phones, cars,
and appliances with built in computers can be programmed to better meet individual needs. A smart
house has a built-in monitoring system that can turn lights on and off, open and close windows, operate
the oven, and more.
With small computing devices available for performing smart tasks like cooking dinner, programming
the VCR, and controlling the flow of information in an organization, people are able to spend more time
doing what they often do best - being creative. Computers can help people work more creatively.
Multimedia systems are known for their educational and entertainment value, which we call
'edutainment'. Multimedia combines text with sound, video, animation, and graphics, which greatly
enhances the interaction between user and machine and can make information more interesting and
appealing to people. Expert systems software enables computers to 'think' like experts. Medical
diagnosis expert systems, for example, can help doctors pinpoint a patient's illness, suggest further
tests, and prescribe appropriate drugs.
Connectivity enables computers and software that might otherwise be incompatible to communicate
and to share resources. Now that computers are proliferating in many areas and networks are
available for people to access data and communicate with others, personal computers are becoming
interpersonal PCs. They have the potential to significantly improve the way we relate to each other.
Many people today telecommute that is, use their computers to stay in touch with the office while they
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are working at home. With the proper tools, hospital staff can get a diagnosis from a medical expert
hundreds or thousands, of miles away. Similarly, the disabled can communicate more effectively with
others using computers.
Distance learning and videoconferencing are concepts made possible with the use of an electronic
classroom or boardroom accessible to people in remote locations. Vast databases of information are
currently available to users of the internet, all of whom can send mail messages to each other. The
information superhighway is designed to significantly expand this interactive connectivity so that people
all over the world will have free access to all these resources.
People power is critical to ensuring that hardware, software, and connectivity are effectively integrated
in a socially responsible way. People - computer users and computer professionals - are the ones who
will decide which hardware, software, and networks endure and how great an impact they will have on
our lives. Ultimately people power must be exercised to ensure that computers are used not only
efficiently but in a socially responsible way.
UNIT 2 Computer Architecture
INTRODUCTION
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).
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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.
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 normal 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 (computing devices connected
together). 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. Note that the American spelling of disk is commonly used, although the British spelling,
disc, is sometimes 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 - see Unit 17). 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.
When specifying a computer the following are normally quoted:
a the speed of the processor (MHz - megahertz, GHz - gigahertz)
b the capacity (size) of the memory (MB – megabytes)
c the capacity (size) of the magnetic storage devices e.g. hard disk, floppy disk (MB - megabytes, GB
– gigabytes)
d the speed of the optical storage devices e.g. CD-ROM, DVD (given as a multiple of the speed of
the first devices produced e.g. 24x = 24 times, 12x = 12 times)
e the display monitor size (measured in inches diagonally across the screen surface)
f the monitor image quality (resolution) given by the number of pixels (picture elements) that are
used across and down the screen e.g. 800 x 600, or by the graphics standard used e.g., VGA (video
graphics array), SVGA (super video graphics array)
g the graphics card memory size (MB - megabytes)
h the speed of the modern (measured in kbps - kilobits per second)
Two different number systems are used in computer specifications:
a The decimal system, which consists often digits from 0 to 9, is used for measuring speed.
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b The binary system, which only has two digits (1 and 0), is used for measuring capacity.
The following prefixes are also used in measurements:
Decimal system Binary system
kilo 103 = 1 thousand 210 = 1,024
mega 106 = 1 million 220 =1,048,576
giga 109 = 1 thousand million 230 = 1,073,741,824
e.g. 1.7 GHz = one point seven thousand million cycles per second 256 MB = 256 x 220 bytes =
approximately two hundred and fifty six million bytes
Communication is provided between applications programs (wordprocessors, drawing programs,
etc.) and the computer hardware (the physical components of a computer system) by a set of programs
collectively known as the operating system e.g. Microsoft Windows, MacOS.
READING
How to read a computer ad
1. Intel Pentium IV 1.7 GHz Processor
2. Mini Tower Chassis
3. 256MB Rambus RDRAM
4. 60GB Hard Drive
5. Embedded Intel 3D Direct AGP video with 64MB SDRAM
6. 64-voice wavetable sound
7. 48 X CD-ROM Drive
8. 19" (1 7.9" VIS) Colour SVGA monitor
9. Microsoft Windows XP
10.1.44MB 3.5" Floppy Drive
11.Microsoft Intellimouse
12.105-key keyboard
13.The main processing chip that operates at a clock speed of 1.7 thousand million cycles per second.
14.A small size of tall and narrow style of case containing the computer system.
15.256 megabytes of Rambus dynamic type of main memory chips that constitute the computer RAM.
16.A hard drive internal storage device with a capacity of approx. 60 thousand million bytes.
17.A video controller for controlling the monitor screen that is built on to the computer motherboard. It can
process 3D images using the AGP type of video bus interface. It also contains approx. 64 million bytes
of synchronous dynamic random access memory that is used as video memory.
18. A sound card that has 64 voices and generates sounds using the wave table system.
19.A CD-ROM storage device that operates at 48 times the speed of the original CD-ROM devices.
20.A colour monitor for displaying output on a screen at resolutions determined by the SVGA standard.
The diagonal measurement of the whole screen is 19 inches but the diagonal measurement of the
actual viewable area of the screen is only 17.9. inches.
21.The operating system that is used to control the system.
SPECIALIZED READING
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 put of memory. One of the most important techniques for getting around this bottleneck is
the memory cache.
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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 acce
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