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A computer is an electronic device that can receive a set of instructions, or program, and then carry out this program by performing calculations on numerical data or by compiling and correlating other forms of information.
The modern world of high technology could not have come about except for the development of the computer. Different types and sizes of computers find uses throughout society in the storage and handling of data, from secret governmental files to banking transactions to private household accounts
. Computers have opened up a new era in manufacturing through the techniques of automation, and they have enhanced modern communication systems. They are essential tools in almost every field of research and applied technology, from constructing models of the universe to producing tomorrow's weather reports, and their use has in itself opened up new areas of conjecture. Database services and computer networks make available a great variety of information sources
.The same advanced techniques also make the invasions of privacy and restricted information sources possible, and computer crime has become one of the many risks that society must face if it is to enjoy the benefits of modern technology.
A microcomputer is a desktop or notebook size computing device that uses a microprocessor as its Central Processing Unit, or CPU. Microcomputers are also called Personal Computers(PCs）, home computers, small business computers, and micros. The smallest, most compact are called laptops. When they first appeared, they were considered single user devices, and they were capable of handling only 4, 8, or 16 bits of information at one time. More recently the distinction between microcomputers and large, mainframe computers as well as the smaller mainframe type systems called minicomputers has become blurred, as newer microcomputer models have increased the speed and data handling capabilities of their CPUs into the 256 bit, or even much more bit multiuser range.
Microcomputers are designed for use in homes, schools, and office settings. Within the home, they can serve both as a tool for home management balancing the family checkbook, structuring the family budget, indexing recipes and as a recreational device playing computer games, cataloging records and books. School children can use microcomputers for doing their homework, and in fact many public schools now employ the devices for programmed learning and computer literacy
courses. Small businesses may purchase microcomputers for word processing, bookkeeping, the storage and handling of mailing lists and so on.
Desktop Computer
A
desktop
computer
is a personal computer in a form intended for regular use at a single location, as opposed to a mobile laptop or portable computer. Prior to the wide spread of microprocessors a computer that could fit on a desk was considered remarkably small. Today the phrase usually indicates a particular style of computer case. Desktop computers come in a variety of styles ranging from large vertical tower cases to small form factor models that can be tucked behind an LCD
monitor. In this sense, the term“desktop”refers specifically to a horizontally-oriented case, usually intended to have the display screen placed on top to save space on the desk top. Most modern desktop computers have separate screens and keyboards. A specialized form of desktop case is used for home theater PC systems, incorporating front-panel mounted controls for audio and video.
Personal Digital Assistant(PDA)
A
personal
digital
assistant
(PDA)is a handheld computer, also known as a palmtop computer. Newer PDAs also have both color screens and audio capabilities, enabling them to be used as mobile phones, smartphones, web browsers, or portable media players. Many PDAs can access the Internet, intranets or extranets via Wi-Fi
, or Wireless WideArea Networks(WWANs
）. Many PDAs employ touch screen technology.
Tablet
PC
A Tablet PC is a laptop mobile computer, equipped with a touchscreen or graphics tablet/screen hybrid technology which allows the user to operate the computer with a stylus or digital pen, or a fingertip, instead of a keyboard or mouse. This form factor offers a more mobile way to interact with a computer. Tablet PCs are often used where normal notebooks are impractical or unwieldy, or do not provide the needed functionality.
Laptop
A laptop(also known as a notebook)is a personal computer designed for mobile use small enough to sit on one's lap. A laptop includes most of the typical components of a typical desktop computer, including a display, a keyboard, a pointing device, a touchpad, also known as a trackpad, or a pointing stick, as well as a battery, into a single small and light unit. The rechargeable battery required is charged from an AC/DC adapter and typically stores enough energy to run the laptop for several hours.
A minicomputer is a mid-level computer built to perform complex computations while dealing efficiently with a high level of input and output from users connected via terminals. Minicomputers also frequently connect to other minicomputers on a network and distribute processing among all the attached machines. Minicomputers are used heavily in transaction processing applications and as interfaces between mainframe computer systems and wide area networks.
A mainframe computer is a high level computer designed for the most intensive computational tasks. Mainframe computers are often shared by multiple users connected to the computer via terminals. The most powerful mainframes, called supercomputers, perform highly complex and time-consuming computations and are used heavily in both pure and applied research by scientists, large businesses, and the military.
·Servers
A server usually refers to a computer that is dedicated to providing a service. For example, a computer dedicated to a database may be called a“database server”.“File servers”manage a large collection of computer files.“Web servers”process web pages and web applications. Many smaller servers are actually personal computers that have been dedicated to providing services for other computers.
A server is a computer program that provides services to other computer programs and their users in the same or other computer. The physical computer that runs a server program is also often referred to as server.
Services can be supplied centrally by the use of a server;in other cases all the machines on a network have the same status with no dedicated server, and services are supplied peer-to-peer
.
·Workstation
Workstations are computers that are intended to serve one user and may contain special hardware enhancements not found on a personal computer.
It is a high-end microcomputer designed for technical or scientific applications. Intended primarily to be used by one person at a time, they are commonly connected to a local area network and run multi-user operating systems. The term workstation has also been used to refer to a mainframe computer terminal or a PC connected up to a network.
Historically, workstations had offered higher performance than personal computers, especially with respect to graphics and CPU power, memory capacity and multitasking ability. They are optimized for display and manipulation of different types of complex data such as 3D mechanical design, engineering simulation(e. g.computational fluid dynamics）, animation and rendering of images, and mathematical plots. Consoles consist of a high resolution display, a keyboard and a mouse at a minimum, but also offer multiple displays, graphics tablets, SpaceBalls, etc. Workstations are the first segment of the computer market to present advanced accessories and collaboration tools.
·Embedded computers
Embedded computers are computers that are a part of a machine or device. Embedded computers generally execute a program that is stored in non-volatile memory and is only intended to operate a specific machine or device. Embedded computers are very common. Embedded computers are typically required to operate continuously without being reset or rebooted, and once employed in their task the software usually cannot be modified. An automobile may contain a number of embedded computers;however, a washing machine and a DVD player would contain only one. The central processing units(CPUs)used in embedded computers are often sufficient only for the computational requirements of the specific application and may be slower and less expensive than CPUs found in personal computers.
·Supercomputer
In computer science, supercomputers are large, extremely fast, and expensive computers used for complex or sophisticated calculations, typically, machines capable of pipelining instruction execution and providing vector instructions. A supercomputer can, for example, perform the enormous number of calculations required to draw and animate a moving spaceship in a motion picture
. Supercomputers are also used for weather forecasting, large scale scientific modeling, oil exploration and so on and so like.
One ongoing trend in computer development is microminiaturization, the effort to compress more circuit elements into smaller and smaller chip space. Researchers are also trying to speed up circuitry functions through the use of superconductivity, the phenomenon of decreased electrical resistance observed as objects exposed to very low temperatures become increasingly colder
. The fifth-generation computer, the effort to develop computers that can solve complex problems in what might eventually be called creative ways, is another trend in computer development, the ideal goal being true artificial intelligence
.
Quantum Computer
A quantum computer
, quite different from classical current computers, is a device that harnesses physical phenomenon unique to quantum mechanics to realize a fundamentally new mode of information processing. In a quantum computer, the fundamental unit of information called a quantum bit(or qubit）, is not binary but rather more quaternary in nature. A qubit can exist not only in a state corresponding to the logical state 0 or 1 as in a classical bit, but also in states corresponding to a blend or superposition of these classical states. In other words, a qubit can exist as a 0, a 1, or simultaneously as both 0 and 1, with a numerical coefficient representing the probability for each state.
DNA Computer
DNA
computing
is a form of computing which uses DNA, biochemistry and molecular biology, instead of the traditional silicon-based computer technologies. DNA computing, or, more generally, molecular computing, is a fast developing interdisciplinary area and is fundamentally similar to parallel computing in that it takes advantage of the many different molecules of DNA to try many different possibilities at once. And DNA computers are faster and smaller than any other computer built so far.
Optical Computer
An optical computer is a computer that uses light instead of electricity(i. e. photons rather than electrons )to manipulate, store and transmit data. Optical computer technology is still in the early stages:functional optical computers have been built in the laboratory, but none have progressed past the prototype stage.
Molecule Computer
A molecular computer that uses enzymes to perform calculations has been built and it is believed enzyme-powered computers could eventually be implanted into the human body and used to, for example, tailor the release of drugs to a specific person's metabolism.
It used two enzymes to trigger two interconnected chemical reactions. Two chemical components-hydrogen peroxide
and glucose
-were used to represent input values A and B. The presence of each chemical corresponded to a binary 1, while the absence represented a binary 0.The chemical result of the enzyme-powered reaction was determined optically.
I. Choose the best answer :
1. We can learn from the text that a computer can_____.
A. be best used as a calculating device
B. be best used in word processing
C. find uses almost everywhere
D. have intelligence of its own
2. How many types of regular computers are introduced in this text?
A. 1
B. 2
C.3
D. 4
3. Which of the following computers is the smallest according to the text?
A. a palmtop
B. A desktop
C. A minicomputer
D. A laptop
4. Which of the following is implied but not stated?
A. Pupils can use computers to do their homework.
B. Advanced techniques may bring both benefits and harms to our society.
C. The distinction between micros and mainframes has become blurred.
D. A great variety of information sources are available on computer networks.
5. We can infer that_____.
A. there will be no distinction between micros and mainframes in the future
B. a future computer can use several CPUs to work for it at the same time
C. the fifth generation computer will be produced within 2 years
D. electronic computers will soon be out of date
6. We can draw a conclusion that_____.
A. to continue to develop and improve computer networks is one of our aims in the near future
B. the development of computers has already reached its peak
C. electronic computers have hindered the development of molecular computers
D. our society would have developed faster without computers
7. Microminiaturization of future computers will be realized through the use of_____.
A. superconductivity
B. molecules
C. DNAs
D. smaller chips
8. Future computers will be made very fast by employing_____.
A. superconductivity
B. smaller chips
C. more elements
D. networks
9. A future computer scientist might also be_____.
A. a geologist
B. a bioengineer
C. a politician
D. a social worker
10. The main purpose of the fifth generation computer effort is_____.
A. to use molecules instead of electronic elements
B. to express logical symbols in the way of chemical units of DNA
C. to obtain true artificial intelligence
D. to take the place of human thoughts
II. True or false questions :
1. It is unimaginable to do research nowadays without the help of a computer.
2. With advanced techniques, no one would be able to invade restricted information sources.
3. A CPU, usually regarded as the heart of a computer, can be a microprocessor.
4. A PC can be a laptop or a desktop.
5. In many schools we employ computers for schoolchildren to learn how to use them.
6. Computers seem to be put to little use in private homes.
7. One of the drawbacks of a computer is that it cannot be used as a recreational device.
8. It seems that there is less distinction between a mainframe and a supercomputer.
9. An optical computer is a computer that uses electricity i. e.electrons, to manipulate, store and transmit data.
10. We have used molecular computers to solve more sophisticated problems successfully.