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Personal computer


Personal computer
Computer today took the same position as the telephone, the car, and a television. But, apparently, it is only the first harbingers of the era of total computerization, which is coming in the next few decades. In all respects, the computer is a phenomenon quite unusual. Perhaps no other technological invention before it did not show itself so rapidly, did not develop so fast and not permeated so many facets of our lives. Computers have become indispensable in the office work, business, military affairs, science, technology, and hundreds of other occupations. They rapidly instilled in the arts, politics and sports. Great importance that computers had to take in people's private lives, in their mutual communication and rest. But this, perhaps, is the only training or the first harbinger of immense information revolution, which is coming in the next few decades. Because that's what the computer will have to play the role of a magic key, the magic of the window through which every single individual through a global computer network will be able to access all the wealth of information accumulated by mankind.

Although nowadays computing operations far from home and in any case is not the only sphere of computer application, historically it owes its origin is the development of computer technology. first generation computer, the hard and slow-moving calculators, were the pioneers of computer technology. As we remember, they quickly left the scene, and not finding widespread commercial use because of insecurity, high cost and difficult programming. They were on the second generation of computers had to change. The element base of these machines have become semiconductors. The switching speed is already at first imperfect transistors were hundreds of times higher than that of vacuum tubes, reliability and efficiency - also several orders of magnitude higher. It immediately expanded the scope of the computer. Now you can install them on ships and airplanes. Demand for computers grew rapidly. The first production of computer transistors appeared in 1958 simultaneously in the USA, Germany and Japan. In 1962 it began mass production of integrated circuits, but on an experimental computer chips 587 was created in 1961. In 1964, IBM has adjusted release of IBM-360 machines - the first mass series of computers on the integral elements. For the first time then it became possible to connect the machine to the complexes and without any alterations to transfer programs written for one computer, to any other of the series. Since standardization of hardware and computer software was implemented. In total, the series consists of 9 cars with different levels of difficulty lead time addition operation from 206 to 0, 18 microseconds. 19 thousand computers in this series of different classes were sold just a few years. From this we can conclude that with the advent of the third generation computers has increased demand for even more. They began to acquire many industrial and commercial firms. microprocessors, "Intel" company was established in 1971, we had an extraordinary commercial success, since at low cost solution to provide a sufficiently large range of operational tasks. In 1976 came the first fourth-generation machines to large-scale integrated circuits - US "Cray-1" and "Cray-2" with a speed of 100 million instructions per second. They contain about 300 thousand chips (ICs).

So in a nutshell I looked prehistory PC. The occurrence of this type of machinery nobody planned. He fell down, so to speak, out of the blue. It all began in the same 1976, when two enterprising twentysomethings American equipment, which had no special education, Stephen Wozniak and Steve Jobs, created in a primitive workshop in an ordinary garage, the first small but promising personal computer. He was named "Apple" ( "Apple") and originally intended for video games, but also had the opportunity to program. Later, Jobs founded the company "Apple Computer", which was the first to mass-produce personal computers. Demand for them has exceeded all expectations. In a short time, the company Steve Jobs has become a large and thriving enterprise. This prompted other firms to pay attention to the personal computer market. On sale there was a set of models "desktops" very different concepts. In 1981, his first personal computer IBM PC released by IBM. His success in the world has been tremendous, thanks in no small measure contributed to a very good 16-bit, the Intel 8088 microprocessor and beautifully designed «Microsoft» software company. The next model PC / XT, released in 1983, had 640 KB RAM, hard drive and high performance. In 1986, there was even more perfect PC / AT model based on the Intel 80286-microprocessor. By the end of the decade of IBM computers have become the most widespread and popular.

What is a PC? Regardless of the complexity of its computer block diagram can be divided into three major divisions: Memory, CPU and peripherals. The memory serves to memorize numbers and logical instructions (which are also stored in it in a numerical code) and works in constant communication with the processor, and when necessary - is connected to the peripheral devices. The physical memory is divided into individual conditional cells in each of which the number is located exactly one fixed length. The machine is characterized by a certain cell microstructure that determines how much of binary information units (bits) can be written into it. The bit corresponds to one bit cell. This part of the cell, as already mentioned, may be in one of two states - they correspond to conventional values ​​"zero" and "one". Eight bits form a larger unit of information - byte, with which you can provide in memory a single letter of the alphabet, number, decimal system, or any punctuation mark, or any other character. Each cell is assigned an address, knowing that you can get to it, enter into it or count the number of his cell. The memory cells are also stored a program consisting of a set of commands - basic requirements that should be doing the machine during each power stroke. Finally, the memory is used for storing intermediate results of solving the problem. Memory work is characterized by two parameters: the capacity (ie, how it is possible to place encoded in binary numbers) and performance (ie how fast these numbers can be written in the memory, and re-extracted therefrom). Performance memory depends on the switching speed of each cell from one state into another.

The amount of memory and its performance, generally speaking, are in contradiction to each other. Other things being equal - the more memory, the less speed, and the more performance - the less memory. Therefore, in today's computer memory is organized as a multi-tiered structure. Usually distinguish the main memory and external. The main memory, in turn, consists of two parts: a random access memory (RAM) and read-only memory (ROM). First, the highest level, is formed of RAM directly connected to the processor. The random access memory is reached the minimum access time to data stored in memory. The second tier of memory - only memory - is connected to the RAM in the event of overload. It serves as a "quick reference" to which from time to time, the microprocessor applies for the right information, or applications. Its speed of several orders of magnitude lower than RAM, but it has a much larger volume. In addition, when you turn off the computer information is not erased from it.

For external memory include a variety of devices capable of storing large amounts of information. This magnetic disk drives, magnetic tape, etc. Their performance can still be several orders of magnitude lower than in the main memory devices, but they can have an enormous capacity - several million or billion bytes. Initially, the computer external memory device served as an ordinary cassette. Who is more likely to use a floppy disk (soft magnetic discs, resembling a small plate, enclosed in a special envelope, and their capacity is about 1-1, 4 MB). The information from the computer's memory on a floppy disk and a floppy disk in the computer's memory is debited via the drive - a special input-output device data. On one tape cassette can be written about the same information as on a floppy disk, but the time of treatment to any program or data element for tape drives is significantly longer than for a magnetic disk drive. This is understandable, since the information on the tape is recorded in the form of a long sequence of bits and for reading the necessary information you need to rewind the whole tape. Now as the external memory devices are widely used hard drives (or hard drives). Their capacity is very large (one disc can store millions of pages of printed text), but they have great speed. The high speed is achieved by the fact that the hard drive is enclosed in a vacuum environment and spun on small bearings. At the heart of it - a tough aluminum plate with a magnetic coating.

The most important unit of any computer is the processor. Its role in the computer microprocessor - an integrated circuit on a silicon chip. The microprocessor implement complex logic, which can be considered the "heart and brain" of the machine. The very name of the unit indicates its active functions. Indeed, the processor deals with the processing program in accordance with the information contained in memory. In each working cycle processor performs one logical or computational operation. Core processor make logic: control unit, arithmetic logic unit, and registers. The control unit directs the operation of all components of the computer; the input of this circuit receives the memory command codes, which are converted into a set of control pulses that are sent to the desired point of a computer circuit. control device operation can be likened to the actions of a conductor in an orchestra, which, guided by the notes of a musical work, with the help of the conductor's baton indicates a group of musicians and independent musicians to start and stop frequently performed piece of music. Arithmetic Logic Unit is designed to perform arithmetic and logic operations. Registers - a digital electronic device for temporary storage of information in the form of a binary number. If the register can store 8 bits at a time (eight binary digits), it is called an eight. If there are 16 hexadecimal, etc. Registers are specialized in their functions. Some are intended to store information other counters act as executable commands, and others are used for storing the executable instructions and addresses etc.

Computer peripheral equipment - a large family of simple and complex devices, the primary meaning of which is to ensure the computer communicate with the outside world. First of all, your computer must be endowed with the capacity of perception of information. This involved the input device. The main device is the keyboard input information. It contains alphanumeric keys to enter numbers and text, as well as the arrow keys, switch modes and registers, and for other purposes. The keys on the keyboard are arranged in much the same way as on a typewriter.

The primary device for displaying information is display or monitor. Most modern displays is based on a construction of its cathode-ray tube and a device similar to a TV. In today's computers is very important in the dialogue with the user's computer mouse discharged. The mouse is a small device, sliding on a flat surface. The relative coordinates of its displacement is transmitted to a computer and processed so as to control the movements on a display screen of a dedicated token, called cursor. This method of selecting positions and directions of objects on the screen is very convenient. With this organization, the dialog is displayed several pre-compiled versions of commands. Pointing the cursor on one of them, the user gives the command. Thus, the computer can successfully run a man without even a remote idea about programming.

The most commonly occurring data output apparatus is a printing apparatus or printer. But they can also be a plotter (plotter) to display graphs and drawings. The most common matrix printers were common until recently. They are the image of the individual marks is based on the matrix size of 9 by 9 points and blows formed by ribbon finest bars. The number of rods is generally equal to 9, so that points within a matrix of touch, forming a continuous line. On these printers easily create arbitrary fonts and display any graphics. Higher print quality produce inkjet printers, which allow multiple levels of brightness and color printing. The principle of operation of such printers is based on the fact that the control program from a nozzle moving horizontally ejected onto paper tiny droplets of ink to form a desired image.

As with any computer necessary and integral part of the computer is its software. Without the appropriate software on it is almost impossible to work with. The most important class of programs, each computer should be considered as its operating system, which supports the work of all other programs, ensures their interaction with the equipment and allows the user to control the common computer. This system converts the commands and actions performed by the person at the computer, in the short and long set of simple commands that a computer understands. Operating systems not so much. In 1974 it was developed CP / M system, which initiated the creation of operating systems for personal 8-bit computers.

The success of this system is due to its extreme simplicity and compactness, as well as the fact that it required very little memory. In 1981, simultaneously with the IBM PC computers appeared the operating system MS-DOS - Disk Operating System of the company «Microsoft», which was the main operating system for 16-bit computers. Currently, the system created a tremendous amount of applications.

Machine program as it identifies the computer profession at the moment. Since the computer's memory can be in a few seconds to clear old information and programs, and as quickly replace them with the new program and data, the computer, like a fairy tale, it is transformed before our eyes from a calculator to a phenomenal chess player, an accountant or a secretary-typist. Applications are usually addressed to a person who did not develop the programs (and often does not even have a clue about how to do this), but only uses them to solve their specific problems. For example, the various editors to create maximum convenience for working with texts. The user can call on display a variety of documents and work with them as a typewriter. But at the same capabilities and convenience of infinitely increasing. The user, for example, can arbitrarily set the size of the sheet, the margins and indents, select the most diverse print, select, rearrange, and remove part of the text, edit and make changes to automatically check spelling and punctuation, refer to the various dictionaries (which are in the computer's memory) , insert illustrations, etc. etc. It can cause several documents and work with them at the same time, transferring data from one to another. Along with the editor is a set of application-oriented specialists. They allow you to make the economic and mathematical calculations, write music, draw, play, etc.

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