3 Understanding the Computer A computer is a machine that, under a program’s direction, performs four basic operations: input, processing, output, and storage.A program is a list of instructions that tells a computer how perform the four operations.
4 Input The first operation. The computer performs arithmetic or comparison operations on data.Electrical impulses representing words, numbers, images, or sounds.
6 Input Devices: Giving Commands Keyboard & MouseDigital CamerasTouch ScreenWand ReaderStylus PenMicrophoneInput devices are types of hardware that enable you to get programs, data, commands, and responses into the computer’s memory.
8 Types of KeyboardsEnhanced / Extended KeyboardErgonomic KeyboardEnhanced or Extended keyboard– Typically 101 keys laid out in the QWERTY fashion; connected to the computer by a serial cable.Cordless keyboard– Uses infrared or radio wave signals.Ergonomic keyboard– Designed to help prevent cumulative trauma disorder (CTD) or damage to nerve tissues in the wrist and hand due to repeated motion.
10 Pointing DevicesPointing devices enable the user to control the movements of an on-screen pointer.They enable the user to initiate commands and to respond to the active program.They are used to provide input in graphics programs.
11 Types of MiceCordless MousePS/2 MousePS/2– Most commonly used; connects to PS/2 port or USB port.Serial– Not commonly used; connects to a serial port.Bus– Obsolete; connects to an expansion card.Cordless– Uses infrared signals; must be within sight of the receiving port.
12 How a Mouse Works Mouse buttons enable the user to initiate actions. Clicking (left-, right-, or double-clicking) allows the user to select an item on the screen or open a program or dialog box.Click and drag– Holding down the left mouse button and moving the mouse enables the user to move objects on the screen.A mechanical mouse uses a rotating ball to position the pointer on the screen.An optical mouse uses laser light to determine the pointer position.
13 Other Types of Pointing Devices Touch ScreenFoot MouseTouch PadJoystickTrackballPointing StickPen
14 Speech RecognitionSpeech recognition is a type of input in which the computer recognizes words spoken into a microphone.Special software and a microphone are required.Latest technology uses continuous speech recognition where the user does not have to pause between words.
15 Optical Input Devices Digital Video Digital Cameras Web Cams Click on the picture to play videoDigital VideoDigital CamerasWeb CamsVideoconferencing
16 Other Input DevicesFax MachinesScannersHandheldFlatbed
17 Processing 4 + 16 = 20 728 > 546 Arithmetic Logic The second operation.The computer performs arithmetic or comparison (logical) operations on the data.Performed at a very high speed.
18 Output The third operation. The computer shows the results of the processing operation in a way people can understand.Data is processed into information.
19 Output DevicesOutput devices are peripheral devices that enable us to view or hear the computer’s processed data.Visual output– Text, graphics, and video.Audio output– Sounds, music, and synthesized speech.
20 Visual Display System Video adapter– Responsible for video quality. A visual display system is composed of two parts:Video adapter– Responsible for video quality.Monitor– Displays the video adapter’s output.
21 MonitorA monitor is a peripheral device which displays computer output on a screen.Screen output is referred to as a soft copy.
22 Types of MonitorsCathode-ray tube (CRT)– Resemble televisions; use picture tube technology; inexpensive, but they take up desk space and use a lot of energy.Liquid Crystal Display (LCD or flat-panel)– Cells sandwiched between two transparent layers form images; used for notebook computers, PDAs, cellular phones, and personal computers; expensive, and they take up less desk space and use less energy than CRT monitors.Types of LCD monitors:Passive-matrix LCDActive-matrix LCDGas plasma displayField emission displaysCRTLCD
24 PrintersA printer is a peripheral device that produces a physical copy or hard copy of the computer’s output.Two basic types:Impact printerNonimpact printer
25 Impact PrinterImpact printerDot-matrixAn impact printer is a printer that has a print head that contacts the paper to produce a character.It uses ink ribbon.It is noisy, produces Near-letter quality printouts, and is not commonly used today.Dot-matrix– Pins are used to make characters.
26 Nonimpact PrinterLaserInkjetThe nonimpact printer is the most commonly used printer today.It works quietly compared to an impact printer.Two types of nonimpact printers:Inkjet printer– Also called bubble-jet; makes characters by inserting dots of ink onto paper; letter-quality printouts; cost of printer is inexpensive but ink is costly.Laser printer works like a copier; quality determined by dots per inch (dpi) produced; color printers available; expensive initial costs but cheaper to operate per page.
27 Multifunction Printer A multifunction printer combines the functions of a nonimpact printer, scanner, fax machine, and copier in one unit.
28 PlotterA plotter is a printer that uses a pen that moves over a large revolving sheet of paper.It is used in engineering, drafting, map making, and seismotology.
30 Storage The fourth operation. The computer saves the data or output so that it can be used again later.
31 Memory vs. StorageRAM MemoryHard DriveStorage, also known as mass media or auxiliary storage, refers to the various media on which a computer system can store data.Storage devices hold programs and data in units called files.Files are stored in directories or folders.Memory is a temporary workplace where the computer transfers the contents of a file while it is being used.
32 Why is storage necessary? Retains data when the computer is turned off.Is cheaper than memory.Plays an important role during startup.Plays an input role when starting applications.Is needed for output.Devices can hold a large amount of data.
33 Storage Devices Storage devices are: Hardware that is capable of retaining data when the electricity is turned off.Able to read (retrieve) data from a storage medium (disk/tape).Able to write (record) data to a storage medium.
34 How Computers “Think” Computers use algorithms to solve a problem. Algorithms are step-by-step procedures.
35 The Information Processing Cycle Input Processing Output StorageThe computer performs the four basic operations (input, processing, output, and storage).Two types of processing cycles:Batch processing– A lockstep sequence used by older computers.Interactive processing– Initiating several information processing cycles in a single session; used by modern computers.
36 Computer SystemSoftwareHardwareA collection of related computer components that are designed to work together.A system includes hardware and software.
37 HardwareHardware is the computer’s physical components.The components include:Input devices– Enable users to enter data into the computer for processing.Processing circuitry– Components located in the system’s case that transform data into information.Output devices– Peripherals that show the results of processing.Storage devices– Used to store all the programs and data that the computer uses.Communication Devices– Used to move data between computers.
38 Processing: Transforming Data into Information Key TermsCentral processing unit (CPU)– The computer’s processing circuitry. It is also called a microprocessor.Chip– A wafer of silicon that contains a complex electronic circuit.Motherboard– The computer’s main circuit board.Memory– Chips that store program instructions. Random access memory (RAM) is the most important type.Expansion slots– A receptacle designed to accept a plug-in expansion card.Expansion card– Used to connect peripherals (input/output devices) to the motherboard.
40 CPUs at WorkControl Unit– Manages four basic operations (fetch, decode, execute, and write-back).The machine cycle or processing cycle:Instruction CycleFetch- Gets next program instruction from the computer’s memory.Decode- Figures out what the program is telling the computer to do.Execution CycleExecute- Performs the requested action.Write-back (Store)- Writes (stores) the results to a register or to memory.Arithmetic-Logic Unit (ALU)– Performs basic arithmetic or logic operations.Adds, subtracts, multiplies, and dividesCompares data to determine which one is larger or smaller.
41 The Processing Cycle Click to animate. Click one time only Control unitALUMemory
42 The Motherboard Microprocessor Keyboard / Mouse Ports Printer Port Click on terms to view larger images and informationMicroprocessorKeyboard / Mouse PortsPrinter PortMemory SlotsVideo PortAGP SlotPCI SlotsChipset
45 Output: Displaying the Information Key TermsMonitors– Display processing results on a screen.Cathode ray tube– Monitor similar to televisions.Flat-panel displays (LCD)– Monitor that uses liquid crystal diodes.Speakers– Enable the user to hear the results of sound processing.Printers– Generate output on paper.Impact printers– Print heads strike a ribbon to produce an image.Nonimpact printers– Transfer the image to the paper.Inkjet printersLaser printers
47 Storage: Holding Programs and Data for Future Use Key TermsStorage media– Includes all types of storage media.Magnetic storage media– Uses magnetically sensitive material.Optical storage media– Uses a laser beam to scan pits etched into a disc.Writing– Recording data to a disk.Reading– Playing back information on a disk.Floppy disk– Removable storage medium.CD ROM– Optical storage medium.
48 Storage Devices Hard Drive CD / DVD Drive Floppy Disk Drive Zip Drive Micro DriveTape DriveJazz Drive
49 Communications Devices Key TermsComputer network– Two or more computers linked by some type of connection.Modem– Enables access to other computers by way of a telephone line.Network interface card (NIC)– Enables computers to connect to each other in a limited geographic area.Local area network (LAN)– Computers connected to each other within a building or group of buildings.
50 Communications Devices ModemNetwork Interface Card– NIC
51 Types of Computers Workstation Desktop– PC, Microcomputer Notebook– LaptopPersonal Digital Assistant– PDA, Handheld, Pocket PC