Subject:Introduction of computer systems. Architecture of computer systems
1.The history of the development of computer
2.The basic configuration of the PC
3.Input, output and storage devices.
Review of the computer systems
All modern computer systems are built on three principles of John background of Neyman : programmatic management, homogeneity of memory and addressness.
The structure of the computer systems consists of three basic elements (see Picture 1.1, "Components of the computer systems") :
Processor
Carries out control after the actions of computer, and also performs the duty of processing of data according to the program. In the modern systems there can be one and more central processing units.
Conventional memory
The programs and data are kept in her. As a rule there is temporal (information is saved, while energised).
Input-outputs
Serve for communication of data between a computer and external surroundings consisting of subsidiary devices, bulk storage, of communication equipment, terminals, is included in the number of that.
System tire
The enumerated components of the computer system unite by means of system tire. It is structures and mechanisms, providing cooperation between a processor, conventional memory and input-outputs.
Picture 1.1 "Components of the computer systems"
Central processor extracts the program from memory, decodes and carries out commands, passes to the next command according to a current command.
At any time, the processor can execute only one program. Many modern operating systems are multitasking, at the same time can run multiple tasks.
Computer memory configuration is mainly determined by three parameters: volume, speed, cost.
Picture 1.2 .Classification ofmemory
Of particular importance is the main memory - it contains all the executable programs and data to them. The program can access any memory location in its address space. There are several types of address spaces: a real (physical memory corresponds to cells) and virtual (somehow projected onto the real address space).
Interaction with the IO devices can occur in three ways: a programmable input and output, input and output via an interrupt, direct memory access.
The evolution of computer systems
The evolution of computer systems can be divided into five stages:
• First-generation systems. The first electronic computer, ENIAC, was born in 1946. The first computer designed for sale to business enterprises and other organizations. YUNIVAK (UNIVAC), was created in the early 50s and was used to summarize the results of the US Census. These computers are the first generation to work in the vacuum tube, the earliest electronic elements, which, unfortunately, are often burned out, isolated lot of heat and consume a lot of energy. They used sophisticated programming techniques
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• Second generation systems. In the 50s there were transistors, which have been used in the new generation of computers, which have become cheaper, smaller and more reliable than their predecessors. Facilitating their programming, as these new machines use language understandable for ordinary people.
• Third generation systems. By the early 60s computers entered the next stage of development. These computers used integrated circuits, which reduced the size of cars and heat them. Computers purchased this kind of business equipment, and they have started to appear in accounting, warehouses, laboratories and factories around the world.
• Fourth-generation systems. In 1971, computers have become like those machines that we use today. Many of them work on the basis of microprocessors. The development of the fourth generation of systems has led to the birth of personal computers, "Apple I" and "ABM". These are computers that we use today.
• Fifth-generation systems. This class of cars, which embodies the latest achievements of computer technology focus of the development of artificial intelligence and other advanced achievements.
A computer is an electronic machine that makes mathematical calculationsand logical comparisons quickly and without any mistakes. Computers takeinformation (called data), process it, and show the results of the processing.
They can store the results forever. For these reasons,computers have become a part of our lives.Computers consist of two parts,hardware and software. Hardware isthe physical parts of the computer.Software is the programs in thecomputer. Software uses hardware toperform operations for the computeruser. The relation between hardwareand software is like the relationbetween our body and our spirit.
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Computers can store information in two different ways: in permanentstorage (for example, on a disk or a CD), and in temporary storage, also calledthe computer’s memory, or RAM. Data in temporary storage only lasts as longas the computer is switched on. This is why the storage is called temporary.When you switch on a computer, first a special piece of software called theoperating system is copied (loaded) from permanent storage to the RAM. Thecomputer gets data from an input device such as a keyboard, mouse, harddisk, or scanner, and makes all the calculations and the comparisons in thecentral processing unit(CPU). The CPU is like thecomputer’s brain. It usesthe RAM to maintain thedata. When the CPU hasprocessed the data, itsends the results to anoutput device such as amonitor, hard disk, orprinter.When you switch acomputer off, thecomputer copies anyimportant data in theRAM back to permanentstorage.
The physical parts of a computer are called hardware. In this lecture, we will divide the different types of hardware into four groups: the system unit, input devices, output devices, and storage devices.
The system unit contains the main components of the computer, such as the mainboard, CPU, RAM, video card, hard disk, disk drives, and the power supply. It can also contain optional components such as a sound card or a network card.
We use input devices to give data to the computer. The most common input devices are the keyboard and the mouse. Other types of input device area scanner, joystick, light pen, touch screen, webcam, and digital camera.
Output devices are the components where the computer shows the results. A printer, plotter, and loud speaker are all output devices.
Storage devices are used to store data permanently. A hard disk, floppy disk,CD-ROM, DVD-ROM, Zip disk, and tape cartridge are examples of storage devices.
Some hardware parts (such as the CPU, mainboard, RAM, power supply, keyboard, graphics card, and hard disk) are necessary for computer to work. Some parts are optional and simply increase a computer’s functionality. A printer, a modem, and a network card are examples of optional components.
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The System Unit
All of the main components of a computer are grouped together in the system unit. For instance, the system unit includes the computer system’s motherboard (including the processor), and items such as hard disks, floppy disks, and CD-ROM drives, etc.
Chassis
The chassis is the metal and plastic box that contains the system unit. Mostpeople don’t think that the chassis is an important part of the computer.However, it is not just the shell of your computer, it supports all the internalparts. It also protects your system from the outside world and helps to keep thesystem unit components cool. The closed design and good air flow inside thechassis are especially important for components such as the CPU and harddrive, which can get very hot when they are working.
Mainboard
The mainboard (also called the motherboard, or systemboard) is the biggest board inside your system unit. All themain components of your computer connect to themainboard. The CPU is normally situated on yourmainboard along with all the other electronic components.
All the other boards (cards) in your computer connect tothe mainboard. Other items, such as the hard disk, areattached to the mainboard either directly or via cables.Mainboards are getting smaller and smaller as thecomponents become more integrated. Nowadays, if youopen up a system unit it can look quite empty.The ROM-BIOS (Read Only Memory-Basic Input Output System) chip is aspecial microchip on your computer’s mainboard. It contains software thatallows your computer to work with your operating system. For example, itcopies your operating system into RAM when you switch on your computer.Buses are data paths on the motherboard that connect the CPU to thedifferent parts of the mother board, such as the chips and cable connections.
Expansion slots are sockets on the mainboard which allow you to extend thecomputer’s features and capabilities. Expansion slots hold expansion cards(such as a video card, sound card, or network card) and connect them to thebuses. Laptops and other portable computers use special expansion slots calledPCMCIA slots, which accept small expansion cards called PC CardsSerial ports are sockets located at the back of your computer that allow you to connect items such as modems to the computer. Serial ports are commonlylabeled COM1 or COM2.
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Parallel ports are sockets located at the back of yourcomputer that enable you to connect items such asprinters to the computer. Parallel ports are commonlylabeled LPT1 or LPT2.
PS/2 keyboard and mouse ports are used to connect akeyboard and mouse to the mainboard.A battery on the mainboard is needed to store someimportant information (such as the date and time, and maybea user password) while your computer is switched off.
An internal speaker connected to the mainboard allows yourcomputer to send you error or warning beeps while it is running.
The USB (Universal Serial Bus) is quite a new item insidea PC. USB ports are located at the back of the system unit. They allow you to plugin devices designed for the USB such as scanners, digital cameras, and printers.The bus arbitrator (chipset) is an integrated circuit on the motherboard. Itcontrols how the mainboard buses are used. If two different devices try to usethe same bus at the same time, there can be a problem. The bus arbitratorprevents this problem.
Central Processing Unit (CPU)
The CPU (Central Processing Unit) is one of the most important componentsinside your computer. It is like the brain of your computer because it performsall the computer calculations. CPU speed is measured in gigahertz (GHz) andhas an important effect on the overall speed of your computer.
Memory (RAM)
RAM (Random Access Memory) is temporary memory thatthe computer uses to store applications and data that are inuse, for example, the operating system, and a word processoror database program. When you create data such as a letteror a picture, the computer stores the data in RAM and thencopies it to the hard disk when you save your work.
IDE Interface
Storage devices such as floppy disk drives, hard disk drives, and CD-ROMdrives usually connect to the computer through an IDE (Integrated DriveElectronics) interface. An IDE interface is a standard way for storage devicesto connect to a computer. IDE is not the original technical name for theinterface standard. It was originally called AT Attachment (ATA) technology,because engineers developed it for the IBM AT computer.
PCI Bus
During the early 1990s, Intel introduced a new bus standard, thePeripheral Component Interconnect (PCI). A PCI bus connects the CPU,memory, and expansion slots on the mainboard. PCI is faster and morereliable than older bus technologies such as ISA.
A PCI bus can connect up to five expansion slots (external devices)to the CPU. Usually there is only one PCI bus on a mainboard, althoughsome mainboards have more.
Graphics Card
Modern computers use a lot of graphics. Many operating systems use agraphical user interface (GUI) as the main interface between the user and thecomputer. You might also enjoy playing video games or creating 3D graphicsand animation. In fact, if you use your computer for anything except basicoffice tasks, you probably use lots of graphics.
A graphics card in a modern PC can connect to the mainboard in one ofseveral different ways: On-board - The graphics chips and memory are part of the mainboard.
PCI - The graphics card plugs into the PCI bus. AGP - The graphics card plugs into a special slot designed especially forgraphics devices. AGP (Accelerated Graphics Port) is a special bustechnology that was developed by Intel as a way to improve theperformance and speed of graphics hardware connected to a PC.
SCSI Bus
Most home and small-office PCs use an IDE hard disk drive and have a PCIbus for adding components to the computer. However, a lot of computers,particularly expensive workstations and older Apple Macintosh computers,use a SCSI (Small Computer System Interface) bus to connect componentssuch as hard disk drives, scanners, CD-ROM drives, printers and tape drivesto the mainboard.
Video Card (Video Adapter)
A video card converts the digital signals in a computer to aspecial format that can be displayed on a monitor. Some videocards also have a TV out to use a TV as a screen. A videocard has its own microprocessor and memory. Today,the size of the memory is up to 128 megabytes.
Power Supply
The power supply is an electrical device thattransforms the standard electricity supply (115-120 Volts AC in the United States, or 220 Volts AC inEurope) into the lower voltages (3.3, or 5 to 12 volts DC)that computer systems require. Personal computer powersupplies are measured in watts. They usually range fromabout 90 watts to 300 watts.
Sound Card
A sound card converts digital sound signals to analog sound signals andsends them to the speakers so that you can hear sounds. If you have amicrophone and suitable software, you can also record sounds. You can alsobuy special software called speech recognition software, which recognizesyour voice and displays the words you say on your monitor. In the future,speech recognition software might replace the keyboard.
Network Interface Card (NIC)
A network interface card allows computers to communicate with eachother through cables. It converts digital signals to analog signals and sendsthese analog signals to other network interface cards in other computers.
Those cards convert the analog signals back to digital signals. In this way,computers can communicate with each other. Network interface cards areoften used in offices to connect computers in the same room or building. Tocommunicate over longer distances, office computers usually use amodem.
Modem (Modulator/Demodulator)
A modem is a device that connects yourcomputer to the telephone system. A modemconverts digital data on your computer into analogsignals that can be sent over a telephone line. It also convertsthe analog signals that it receives into digital data. If you want toconnect to the Internet using a telephone line, you will need a modem.
TV Card
TV cards usually have twofunctions, TV decoding and TVtuning. The TV decoder transfers thepicture that is on the screen to a TV.This is sometimes useful forbusiness presentations. The TVtuner allows you to watch TVchannels on the monitor so that yourmonitor becomes like a TV.
PC Card
A PC card is a small, creditcard-sized board that extends acomputer’s ability, for example,by providing more memory, orworking like a modem. PC cardsare particulary useful for laptops andother personal computers which donot have room for full-size expansion cards. PC cards connect to the outsideof a computer through a special socket, called a PCMCIA slot.
Input Devices
Keyboard
The keyboard is the most common wayto enter information into a computer.Today, standard keyboards have 104 or 105keys. An electronic circuit inside thekeyboard transmits the code of a pressedkey to the CPU.
Mouse
A mouse is another very popular input device, which is used to point tothings and select things on the screen. A small ball underneaththe mouse tells the computer when the mouse is movedacross a surface, and the computer moves the on-screenpointer to follow.There are usually twoor three mousebuttons that you canpress (‘click’) tochoose commands andselect things on the screen.Two mouse clicks close together arecalled a ‘double click’
Scanner
A scanner uses special light sensors to ‘capture’(or photograph) an image and make a digitalcopy, for example on your screen. You canthen use special text or graphics softwareto work with the scanned image. Themost popular types of scanner areflatbed scanners (where the scannermoves the light sensors over theimage), and handheld scanners (where ahuman moves the sensors over the image).
Microphone
A microphone converts sound waves into electrical signals that can beunderstood by your computer’s sound card. The sound card converts theelectrical signals into digital data that your computer can process. Forexample, you can use a microphone to store speech or music on yourcomputer.
Joystick
A joystick is another kind of pointing device, which is often used for computergames. A joystick has a base, usually with one or more control buttons, and avertical stem, which can more in any direction to control the movement of anobject on the screen. The buttons activate different software features.
Light Pen
A light pen is an input device like a pen that isconnected to a computer’s monitor. You can use a lightpen to select items and choose commands on the screenby pointing the pen at the screen, and then either pressing aclip on the side of the pen or touching the screen with the pen (the equivalent ofperforming a mouse click).
Touch Screen
A touch screen is a computer screen which can recognize the location of atouch on its surface. You can touch the screen to make a selection or move acursor. The simplest type of touch screen is made up of a grid of sensing lines,which sense the vertical and horizontal location of the touch. Touch screensare sometimes used in ATM (banking) machines.
Webcam
A webcam is a small digital movie camera mounted on your PC monitorwhich allows you to exchange sound and video across the Internet in ‘realtime’, i.e., as they are recorded.
Digital Camera
A digital camera is a type of camera that stores photographed imageselectronically instead of on traditional film. A digital camera uses a specialdevice to capture an image through the lens when you take a picture. Thecamera stores the image in a storage medium such as a hard disk, which isinside the camera. After the image has been stored, you can transfer it bycable to the computer using software supplied with the camera.
Output Devices
Monitor
A monitor, or computer screen, is avery common type of output device. Amonitor displays images which havebeen generated by the computer’svideo card. The monitor is attached tothe video card by a cable.There are two main types ofmonitor: flat panel monitors, andcathode ray tube (CRT) monitors. Aflat panel monitor uses a liquid crystaldisplay (LCD) instead of a cathode raytube to display data. Flat panelmonitors occupy much less physicalspace than CRT monitors.
Printer
A printer is an output device that prints text and computer-generatedimages onto paper or onto another medium, such as transparent film. Thereare many different types of printer.
Plotter
A plotter is an output device similar to aprinter, but for larger images. Plotters useeither pens, or electrostatic charges andspecial chemicals, to print an image. Penplotters draw on paper or transparent filmwith one or more colored pens. Electrostaticplotters ‘draw’ a pattern of electrostaticallycharged dots on the paper, and then applychemicals to keep the pattern in place.
Speaker
A speaker is an output device that playssound generated by your computer’s soundcard. The speaker is attached to the soundcard by a cable. Most computers also havean internal speaker that is attached to themainboard and which can play simple sounds
Storage Devices
Hard (Fixed) Disk
Hard disks are the main large data storagearea inside your computer. Hard disks areused to store your programs and data
Floppy Disk
Floppy disks are also called diskettes. They are very slow compared to harddisks or CD-ROMs, and hold a smaller amount of data (1.44 megabytes).
CD-ROM
CD-ROM is shortfor Compact Disc-Read Only Memory. ACD-ROM disk canhold a very largeamount of data(usually 650 – 700megabytes). This is thesame as the storage capacityof over 450 floppy disks.
DVD-ROM
DVD stands for Digital Video Disc, orDigital Versatile Disc. A DVD-ROM is like aCD-ROM, but it stores information in adifferent way so that it has a much biggercapacity than a CD-ROM (about 4.7 or 8.5gigabytes of data on one side, or 17 gigabytes on adisk with two sides). Because DVD-ROMs can store so muchdata, they are often used to store movies and animation.
Zip Disk
A Zip disk looks like a floppy disk, but it can hold a lot moredata (up to 100 megabytes). Zip disks can only be read by aspecial drive called a Zip drive. Zip disk technology wasinvented by a company called Iomega.
Magnetic Tape
Computers can read and write data on special cartridges of magnetic tape.A magnetic tape cartridge looks like a music cassette, but it can hold moredata. Computer tape cartridges can only be read by a special tape drive. Theyare often used to make a safe copy ofimportant data that a company oruser doesn’t want to lose.
Lecture 3.
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