Between computers and other machines, and between computers anduserProvide contact between.Input external information into the computer;Take out the information to be output by the computer;Storage and editing of information to be savedExternal informationTo enter the computer.
Basic composition
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(1) Storage medium, which has the physical characteristics of storing information.
A device that inputs data and information to a computer.Is the computer anduserOr other equipment communication bridge.The input device is between the user and the computer systeminformation switchingOne of the main devices of. keyboard,Mouse, camera,Scanner,Light pen,Handwriting input board,joystick,Voice input deviceAll of them belong to input devices. Input Device is a device used by people or external users to interact with computersraw dataAnd a program for processing these numbers into the computer.
Today's computers can receive all kinds of data, eitherNumericalData, or variousNon numerical typeData such as graphics, images, sounds, etc. can be input into the computer through different types of input devices for storage, processing and output.
classification
Computer input devices can be divided into the following categories according to their functions:
Character input device: keyboard;
Optical reading equipment:Optical mark reader，optical character reader；
Analog input device:Speech analog-to-digital conversion recognition system。
Other functions
Peripherals
The following describes the two most commonly used input devices: keyboard andMouseAnd briefly describe the functions of other input devices.
(1) Keyboard is a common input device, which is composed of a set of switch matrices, includingNumber keys、Alphabetic key、Symbolic key、Function keysandControl keyEtc.Each key has its unique code in the computer.When a key is pressed, the keyboardInterfaceSet the key'sBinary codeSend to computerhostAnd display the key characters on the display.When a large number of characters are input quickly and the host has no time to process them, send the code of these characters to the memory firstKeyboard Buffer, and then from thebufferTake out inAnalysis and processing。
Keyboard interfaceCircuits are mostly usedMonolithic microprocessor, which controls the operation of the whole keyboard, such as the self inspection of the keyboard during power onKeyboard Scan、Key codeGeneration, transmission and communication with host.
Peripherals
（2）Mouse(Mouse) is a handheld screenCoordinate positioning equipment, it is adaptationMenu operationSoftware andGraphics Processing EnvironmentThe emergence of an input device, especially in today's popularWindows Graphics Operating System EnvironmentUnder the application of mouse convenient and fast.There are two kinds of mouse in common use, one ismechanicalThe other isPhotoelectric typeOf.
Mechanical mouseA metal ball that can roll is installed on the base of the mouse. When the mouse moves on the desktop,Metal ballFriction with the table top causes rotation.Metal ball and four directionpotentiometerContact, can measureDisplacementTo control the movement of the cursor on the screen.cursorandMouseThe moving direction of is consistent, and the moving distance is proportional.
Optical mouseThe bottom of the is equipped with two small light sources placed in parallel.When the mouse moves on the reflector, the light emitted by the light sourceReflector plateAfter reflection, it is received by the mouse and converted into an electric moving signal to be sent to the computer, so that the cursor on the screen moves with it.Other aspects andMechanical mouseSame.
Optical mark reader
There are two keys and three keys on the mouse.The leftmost key isPick key, the rightmost key isErase keyThe middle key is the menu selection key.Because the mouse is equipped with different software systems, the definitions of the above three keys are different.Generally, the left button of the mouse can determine a position on the screen, which is the display point of the current input character in the character input state;stayGraphics StatusBelow is the reference point for the drawing.In menu selection, left click (pick key) to selectmenu item, you can also chooseDrawing ToolsAnd commands.The system will automatically execute the selected command after making a selection.MouseAble to movecursor, select various operations and commands, and can easily edit and modify the drawing, but cannot input characters and numbers.
Optical mark reader
(3) Other input devices:
Optical mark readerIt is used forPhotoelectric principleThe input device that reads the marks on the paper, including the barcodeReaderAnd computer automatic marking and scoring input equipment.
Graphic (image) scannerIs usingPhotoelectric scanningConvert graphics (images) topixel data An input device that is input into a computer.
At present, some departments have begun toImage inputIt is used in the construction of image database.Such as photo input in personnel files, case data management in the public security system,Digital LibraryThe construction, engineering design and management departments of the engineering drawing management system all use various types of graphics (Fig
Now people are studying how to make computers have human's "hearing" and "vision", that is, to make computers understand what people say and what people write, so that they can receive information in the way that people receive information.For this reason, people have opened up new research directions, includingpattern recognition, artificial intelligenceSignal and image processingAnd based on these research directionsLanguage recognition、Character recognition、natural language understandingAnd machine vision.The essence of language and text input technology is to enable the computer to understand the meaning of the sound heard or the text seen from the sound wave of the language and the shape of the text, that is, to recognize the sound wave and the text.
output device
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definition
output device(OutputDevice) is a component for human computer interaction, which is used for data output.It represents all kinds of calculation result data or information in the form of numbers, characters, images, sounds, etc.The common ones are monitorsprinter、graph plotter、Image output system、Voice output system、Magnetic recording equipmentEtc.
Peripherals
The basic working principles and relevant knowledge of commonly used output device displays and printers are briefly introduced below.
Cathode ray tube display (CRT for short) has occupied a leading position in the display market because of its mature manufacturing process and high performance price ratio.With the gradual maturity of liquid crystal display (LCD for short) technology, it began to emerge in the market.
Operating principle of display
Cathode ray tube displays can be divided intoCharacter displayandGraphic display。The character display can only display characters, not graphics, and generally has only two colors.The graphic display can display not only characters, but also graphics and images.Graphic refers toengineering drawing, that is, a figure composed of points, lines, faces and bodies;Image refers to scenery picture.Both graphics and images on the display are composed of pixels (light spots).display screenThe light spot on theCathode gunEmittingelectron beamstrikePhosphorFilm.Color displayOfKinescopeThe inner side of the screen is composed of red, green and bluephosphorescenceA small triangle (pixel) light emitting film formed by dots.Due to the different intensity of the received electron beamTricolorLight intensity is different, which can produce a pixel with different brightness and color.When the electron beam moves from left to right and from top to bottomprogressive scanningFluorescent screenEvery time you scan, a screen will be displayed, which is called refresh once. As long as the interval between two refreshes is less than 0.01s, the human eye will see a stable screen on the screen.
Operating principle of display
The display is displayed through“Display interface”And bus andhostConnection, the information (character or graphic image) to be displayed is fromDisplay buffer memory(It is generally a storage area of memory, accounting for 16kB) sent to the display interface and converted by the display interface to form controlelectron beamPosition and strength signals.The controlled electron beam willFluorescent screenThe picture can distinguish different colors and light and shade levels.Two important technical indicators of the display are: the number of light spots on the screen, that is, the number of pixels, is called resolution;The depth change level of light spot brightness, namelyGrayscale, can be expressed by color.The level of resolution and grayscale is the standard to measure image quality.
There are many common display interface cards, such asCGA card、VGA card、MGA cardEtc.With VGA (VideoGraphicsArray)Video graphic displayFor example, the resolution of the standard VGA display card is 640 × 480, and the grayscale is 16 colors;The resolution of the enhanced VGA display card is 800 × 600, 960 × 720, and the grayscale can be 256 colors.be-allDisplay interface cardOnly with the corresponding display and display software, can they play their highest performance.
Peripherals
printer
Peripherals
printer(Printer) is the most basic computeroutput deviceone of.It prints the results of computer processing on paper.Printers can be divided into impact type and non impact type according to printing mode.Impact printerIt uses mechanical action to pass the font throughRibbonPrinted on paper, it can be divided into movable type printer andlatticeType printer.Movable type printerIt is to engrave every word on the typing mechanism, which can be spherical, chrysanthemum petal shaped, drum shaped and other shapes.Dot matrix printerDotmatrix printer uses a printing needle to print characters according to the dot matrix of characters.Each character can be composed of m lines × n columns.Generally, characters are composed of 7 × 8 dot matrix, and Chinese characters are composed of 24 × 24 dot matrix.Common use of dot matrix printerPrint headNamed after the number of stitches, such as 9 stitchesprinter, 24 pin printer, etc.
Non impact printerCharacters are printed by various physical or chemical methods, such asElectrostatic induction，Electrocautery、Thermosensitive effect，Laser scanningandInkjetEtc.amongLaser printer(LaserPrinter) andInkjet printer(InkjetPrinter) are the two most popular printers at present. They both form characters and various graphics in the form of dot matrix.Laser printer receives fromCPUThen, laser scanning is carried out, and the information to be output is formed on the magnetic drum into an electrostatic latent image, which is converted into a magnetic signal, so that the toner is adsorbed on the paper, heated and fixed before output.Ink jet printer is to spray ink on paper through a refined nozzle to form characters and graphics.
