Computers and Computer Systems

Computers can be divided into 3 main types, depending on their size and power. Mainframe computers are the largest and the most powerful. They can process large amounts of information very quickly and can be used by many people at the same time. They usually fill the whole room and are sometimes referred to as mainframes or computer installations. They are found in large institutions like universities and government departments.

Minicomputers, commonly known as minis, are smaller and less powerful than mainframes. They are about the size of an office desk and are usually found in banks and offices. They are becoming less popular as microcomputers improve. Microcomputers, commonly known as micros, are the smallest and the least powerful. They are about the size of a typewriter. They can handle smaller amounts of information at a time and are slower than the other two types. They are ideal for use as home computers and are also used in education and business. More powerful microcomputers are gradually being produced; therefore they are becoming the most commonly used type of computers.

A computer can do very little until it is given some information. This is known as the input and usually consists of a program and some data.

A program is a set of instructions, written in a special computer language, telling the computer what operations and processes have to be carried out and in what order they should be done. Data, however, is the particular information that has to be processed by the computer, e.g. numbers, names, measurements. Data brought out of the computer is known as the output.

When a program is run, the computer executes the program step by step to process

the data. The same program can be used with different sets of data.

Information in the form of programs and data is called software, but the pieces of

equipment making up the computer system are known as hardware.

The most important item of hardware is the CPU (Central Processing Unit). This is

the electronic unit at the centre of the computer system. It contains the processor and the main memory. The processor is the brain of the computer. It does all the processing and controls all the other devices in the computer system.

The main memory is the part of the computer where programs and data being used by the processor can be stored. However it only stores information while the computer is switched on and it has a limited capacity.

All the other devices in the computer system, which can be connected to the CPU, are known as peripherals. These include input devices, output devices and storage devices.

An input device is a peripheral, which enables information to be fed into the computer. The most commonly used input device is a keyboard. An output device is a peripheral, which enables information to be brought out of the computer, usually to display the processed data. The most commonly used output device is a specially-adapted television known as a monitor or VDU (Visual Display Unit). Another common output device is a printer. This prints the output of the CPU onto paper.

A storage device is a peripheral used for the permanent storage of information. It has a much greater capacity than the main memory and commonly uses magnetic tape or magnetic discs as the storage medium.

These are the main units of hardware of any computer system whether a small "micro" or a large mainframe system.

At the heart of the computer is the microprocessor. This contains several REGISTERS to store data and an ARITHMETIC LOGIC UNIT (ALU) which manipulates data. It acts as the central processing unit (CPU) of the computer, carrying out a sequence of instructions, called a program.

The program may be stored in memory, as software, or written into the memory from tape or disk. There are two types of memory. Read Only Memory (ROM) which stores software permanently. The software is not lost when the computer is switched off but the stored data cannot be changed. Random Access Memory (RAM) which can be written to and read from. The stored data is volatile. It is lost when the computer is switched off.

The actual computer, its case and printed circuit boards etc are known as hardware. The computer needs to communicate with the outside world. It does this via interfaces which are usually a plug or socket of some type. The computer is a digital device. It may need to communicate with an analogue device such as a loudspeaker or variable speed control. To do this it uses digital to analogue and analogue to digital converters.

Computers can help students perform mathematical operations and solve difficult problems. They can be used to teach courses such as computer-aided design, language learning, programming, mathematics etc.

Computers can help students perform mathematical operations and solve difficult questions.

PCs are also used for administrative purposes: for example, schools use databases and word-processors to keep records of students, teachers and materials. Race organizers and journalists rely on computers to provide them with the current positions of riders and teams in both the particular stages of the race and in the overall competition.

Workstations in the race buses provide timing system and give up-to-the-minute timing information to TV stations. In the press room several PCs give real-time information on the state of the race. Computer databases are also used in the drug-detecting tests for competitors.

Computers store information about amount of money held by each client and enable staff to access large databases and to carry out financial transactions at high speed. They also control the automatic cash dispensers which by the use of a personal coded card, dispense money to clients.

Airline pilots use computers to help them control the plane. For example, monitors display data about fuel consumption and weather conditions. In airport control towers, computers are used to manage radar systems and regulate air traffic. . On the ground, airlines are connected to travel agencies by computer. Travel agents use computers to find out about the availability of flights, prices, times, stopovers and many other details.

4. Read and translate the text using the dictionary:

Transistors

The bipolar junction transistor is the cornerstone of much of today's semiconductor
electronics industry. This form of transistor has been in existence for many years and
is still very widely used in electronic circuits. The bipolar transistor is very versatile
and finds applications in many areas and at a wide range of frequencies.
The bipolar transistor dates back to the middle of the twentieth century when three
scientists named Bardeen, Brattain, and Shockley working at Bell Laboratories in the
USA discovered it. They had been researching an idea for a semiconductor field
effect device, but they had been unable to make it work. They had not succeeded in
making this idea work and as a result they decided to follow other lines of research
and in doing this they developed the bipolar transistor. They succeeded in making it
work in late 1947, and only a week after their initial discovery they demonstrated it in
front of a group of executives at Bell. Laborat today the semiconductor industry is enormous
and vast quantities of money are being invested in new semiconductor device
developments. Although there are many new types of transistor, the bipolar junction
transistor is still in very widespread use.

The bipolar transistor can be made from a variety of types of semiconductors. The original devices were made from germanium, but silicon is widely used today.

MICROELECTRONICS

Thomas Edison's discovery of thermionic emission opened the door to electronic technology. Progress was slow in the beginning, but each year brought new and more amazing discoveries. The development of vacuum tubes soon led to the simple radio. Then more complex systems of communications appeared. Modern systems now allow us to communicate with other parts of the world via satellite. Data is now collected from space by probes without the presence of man because of microelectronic technology.

Sophisticated control systems allow us to operate equipment by remote control in hazardous situations, such as the handling of radioactive materials. We can remotely pilot aircraft from takeoff to landing. We can make course corrections to spacecraft millions of miles from Earth. Space flight, computers, and even video games would not be possible except for the advances made in microelectronics.

The most significant step in modern electronics was the development of the transistor by Bell Laboratories in 1948. This development was to solid-state electronics what the Edison Effect was to the vacuum tube. The solid-state diode and the transistor opened the door to microelectronics.

Microelectronics is defined as that area of technology associated with and applied to the realization of electronic systems made of extremely small electronic parts or elements. The term microelectronics is normally associated with integrated circuits (IC). Microelectronics is often thought to include only integrated circuits. However, many other types of circuits also fall into the microelectronics category. During World War II, the need to reduce the size, weight, and power of military electronic systems became important because of the increased use of these systems. As systems became more complex, their size, weight, and power requirements rapidly increased. The increases finally reached a point that was unacceptable, especially in aircraft and for infantry personnel who carried equipment in combat. These unacceptable factors were the driving force in the development of smaller, lighter, and more efficient electronic circuit components. Such requirements continue to be important factors in the development of new systems, both for military and commercial markets. Military electronic systems, for example, continue to become more highly developed as their capability, reliability, and maintainability is increased.

Millions of people around the world use cellular phones. They are such great gadgets -- with a cell phone, you can talk to anyone on the planet from just about anywhere! These days, cell phones provide an incredible array of functions, and new ones are being added at a breakneck pace. Depending on the cell-phone model, you can store contact information, make task or to-do lists, keep track of appointments and set reminders, use the built-in calculator for simple math, send or receive e-mail, get information (news, entertainment, stock quotes) from the Internet, play games, watch TV, send text messages, integrate other devices such as PDAs, MP3 players and GPS receivers.

But have you ever wondered how a cell phone works? What makes it different from a regular phone? What do all those terms like PCS, GSM, CDMA and TDMA mean? In this article, we will discuss the technology behind cell phones so that you can see how amazing they really are. If you are thinking about buying a cell phone, be sure to check out how a cell phone works and to learn what you should know before making a purchase.

To start with, one of the most interesting things about a cell phone is that it is actually a radio — an extremely sophisticated radio, but a radio nonetheless. The telephone was invented by Alexander Graham Bell in 1876, and wireless communication can trace its roots to the invention of the radio by Nikolai Tesla in the 1880s (formally presented in 1894 by a young Italian named Guglielmo Marconi). It was only natural that these two great technologies would eventually be combined. On a "complexity per cubic inch" scale, cell phones are some of the most intricate devices people use on a daily basis. Modern digital cell phones can process millions of calculations per second in order to compress and decompress the voice stream. If you take a basic digital cell phone apart, you find that it contains just a few individual parts: an amazing circuit board containing the brains of the phone, an antenna, a liquid crystal display (LCD), a keyboard (not unlike the one you find in a TV remote control), a microphone, a speaker, a battery. The circuit board is the heart of the system.

6. Read and translate the text:

The term 'semiconductor' means half-conductor that is a material whose conductivity ranges between that of conductors and non-conductors or insulators. They include great variety of elements (silicon, germanium, selenium, phosphorus and others), many chemical compounds (oxides, sulphides) as well as numerous ores and minerals.

While the conductivity of metals is very little influenced by temperature, conductivity of semiconductors sharply increases with heating and falls with cooling. This dependence has opened great prospects for employing semiconductors in measuring techniques.

Light as well as heat, increases the conductivity of semiconducting materials, this principle being used in creating photo resistances. It is also widely applied for switching on engines, for counting on conveyer belts, a well as various systems of emergency signals and for reproducing sound in cinematography. Besides reacting to light, semiconductors react to all kinds of radiations and they are therefore employing in designing electronic counters.

Engineers and physicists turned their attention to semiconductors more that fifty years ago, seeing in them the way of solving complicated engineering problems. Converting heat into electricity without using boilers or other machines was one of them. This could be done as means of metal thermocouples, but in this way impossible to convert more one per cent of the heat into electricity. The thermocouples made later of conductors more generated ten times as much electricity as the metal ones.

Sunlight like heat can feed our electric circuit. Photocells made of semiconducting materials are capable of transforming ten per cent of sunray energy into electric power. By burning wood, which has accumulated the same amount of solar energy, we obtained only heat fractions of one per cent of electric power. The electricity generated by semiconductor thermocouples can produce not only heat but also cold, this principle being used in manufacturing refrigerators. Semiconducting materials are also excellent means of maintaining a constant temperature irrespective of the surrounding temperature changes. The latter can vary over a wide range, for example, from 59C below OC to 100C above OC. Semiconductors are the youngest field of physical science. Yet even now they are determining the process of radio engineering, automation, chemistry, electrical engineering and many other fields of science and technique.

Date: 2015-12-24; view: 2899