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 Computers and Computer Systems 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 Computers and Computer Systems 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 Computers and Computer Systems 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 Computers and Computer Systems 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 Computers and Computer Systems 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 Computers and Computer Systems (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 Computers and Computer Systems 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 Computers and Computer Systems 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 Computers and Computer Systems-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 Computers and Computer Systems 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:
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 Computers and Computer Systems 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 Computers and Computer Systems 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.