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131 Cards in this Set
- Front
- Back
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Hardware
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Physical Machinery made from electrical circuits
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Software
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Sequences of instructions called programs that can be executed by hardware
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Application Software
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Performs a task for the user
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Bespoke Software
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Written for customer's specific needs
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Bespoke Software -
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More expensive
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Bespoke Software +
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Training Available
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General Purpose Software
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Software that can perform many common tasks
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Special Purpose Software
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Software to support a specific task
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Operating System
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Controls and monitors the running of applications
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Virtual Machine
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Hides the hardware complexity from the user
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Utility Programs
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Perform Specific House-keeping tasks eg. Anti-Virus
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Library Programs
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Compiled Routines that can be used by other programs eg. Print Routine
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1st Gen Language
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Written in machine code
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2nd Gen Language
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Assembly Code uses mnemonics eg. LDA
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Assembler
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Translates Assembly Code to Machine Code
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3rd Gen Language
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High Level Progrramming Languages
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Compiler
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Translates 3rd Gen to Machine Code.
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Interpreter
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Translates and executes line by line
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4th Gen Language
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Declarative
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NOT
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¯
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AND
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.
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OR
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+
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A + B =
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¯(¯A . ¯B)
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A . B =
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¯(¯A + ¯B)
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Processor
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Responsible for executing instructions and surpervising other parts of the system
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Main Memory
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Each location has a unique address and is directly accessible by the processor
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Stored Program Concept
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Program must be in Main Memory to be executed
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Address Bus
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Uni- directional
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Data Bus
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Bi-directional
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Control Bus
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Bi-directional
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I/O Controller
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Electronic Circuit that connects buses to peripheral
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Arithmetic Logic Unit
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Performs Arithmetical and Logical Calculations
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System Clock
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Generates regular pulses to synchronise activities
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Register
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Very fast memory location inside the processor
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General Purpose Register
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Free for programmer's use
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Dedicated Register
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Assigned Permanent Specific Role
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Program Counter Register
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Holds location of next instruction
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Accumulator Register
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Holds the result of the latest calculation
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Current Instruction Register
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Holds the instruction whilst it is decoded and executed
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Memory Address Register
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Holds Memory location address
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Memory Buffer Register
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Holds data transferred to and from memory locations
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Increasing Clock Speed
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Reduces time taken to execute instructions
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Word Length
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number of bits the processor can handle
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Each Parallel wire in the data bus
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is for each bit in word
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Wider data bus
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more data fetched at same time
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wider address bus
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more memory can be addressed at the same time
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LOAD
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Loads a number / the content of a memory location into a register
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ADD
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Adds a number / the content of a memory location to accumulator
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STORE
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Stores the content of accumulator in memory location
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Internet
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A Public network of computer networks and computers using unique IP addresses & TCP/IP
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Packet Switching
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Packets of data
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Router
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Connects networks using same link layer protocol and sends packets over the least congested route
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Gateway
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Connects networks using different link layer protocols
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Protocol
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Set of rules for 2 devices to communicate
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TCP/IP
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4 Layer Protocol Stack
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Application Layer
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1. Handles particular application eg. html
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Transport Layer
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2. Establishes and maintains connection ensuring reliable flow of data
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Network Layer
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3. Adds Source & Destination IP addresses
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Link Layer
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4. Adds Hardware Addresses eg. Network Card
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World Wide Web
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a system of interlinked hypertext documents accessed via the web
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Intranet
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Private computer network used to share information within an organisation
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IP address
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A unique address that identifies a computer on a network
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Domain Name
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A name that identifies an IP address
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DNS Hierarchy
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com / uk = level 1; co / ac = level 2
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Uniform Resource Locator (URL)
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Identifies a resource by its location and protocol
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Uniform Resource Identifier (URI)
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How to access a resource on the internet
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Internet Registry
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Stores domain names & IP addresses
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Internet Registrar
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Registers unique domain names
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Internet Service Provider (ISP)
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Provides access to internet
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Server
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A software process that provides a service requested by a client
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Port Number
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An address for a software process
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Port Used for web servers
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Port 80
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Port Used for POP3 emails
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Port 110
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Port Used for SMTP emails
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Port 25
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Telnet Server
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Used for remote management and to access html
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Web Server
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Retrieve web pages in text form
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Email Server
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Read and send email
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File Transfer Protocol (FTP)
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Transfer files using anonymous & non-anonymous access
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Hypertext Transfer Protocol (HTTP)
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Client machine sends request and server responds
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Hypertext Transfer Protocol over Secure Socket Layer (HTTPS)
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As http but uses secure socket layer to encrypt and decrypt data
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Post Office Protocol 3 (POP3)
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Transfer of email between computer systems but provides more facilities than SMTP
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TCP
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Transmission Control Protocol: Supports public access to email and web pages & allows connection between client and server
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Simple Mail Transfer Protocol (SMTP)
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Transfer of email between computer systems
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Web Browser
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Software that displays a web page by rendering the HTML elements
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Circuit Switching
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A continous link between the sender and reciever of data over a network
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End to end principle
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Two communicating computers are in control of data transmission
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Uniform Resource Name (URN)
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Identifies resource by its name rather than its network location
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Web Page
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Document on WWW written in html and displayed in a web browser
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Hyper Text Markup Language (HTML)
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Defines how a web page is displayed and uses tags to structure it
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Cascading Style Sheet
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Controls how a web page is displayed
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External Style Sheet +
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Updating site is easier
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Robot
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A Movable mechanical structure than can sense its surroundings and manipulate things
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Uses of Robots
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Repetitve precision tasks eg. welding and dangerous tasks eg. bomb disposal
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Digital Rights Management
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Application of control technologies to limit the use of digital media
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Proprietary Software
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Owner places restrictions on its use
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Free Software Foundation promotes
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Run the program for any use
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Mouse
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Detects movement in two directions
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Keyboard
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Components detect keys pressed and send code to computer where it is converted to ASCII
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Bar Code Reader
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Shines light on barcode
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Flatbed Scanner
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Glass pane illuminated from beneath
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Optical Character Reader
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Can convert writing to text characters
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Fingerprint Scanner
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Takes a picture of finger
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Retina Scanner
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Uses infrared light source
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Iris Scanner
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Uses infrared light to capture image
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Optical Mark Reader
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Form passed under light source
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Magnetic Strip Reader
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Reads information encoded magnetically
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Smart Card Reader
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Card Holds integrated circuit chip
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RFID Reader
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Radio Frequency Identification - object has a transpoder to transmit data which is detected by reader
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Touch Sensitive Screen
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Region in front of screen is covered by horizontal and vertical beams of infrared light
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Graphics Tablet
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Stylus is moved across surface of tablet
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Voice Recognition
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Recognises a voice using microphone
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Digital Still Camera
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Senses light intensities across a focal plane and stores on memory card
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Cathode Ray Tube
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Screen has lines of phosphor dots; red
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LCD Flat Screen
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Consists of a matrix of liquid crystal cells each constituting one pixel
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TFT
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Each pixel consists of a tiny film transistor that acts as a switch and a capacitor that holds the electrical charge needed to polarise light in the liquid crystal until refreshed
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Plasma Screen
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Each Pixel controlled by a miniature fluorescent light
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Impact Printer
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Inked ribbon to mark multi-part paper struck by 24 metal pins that form outline of character
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Inkjet Printer
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Uses 4 cartridges to build up line of colour using electrostatics
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Laser printer
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Generates a bitmap of the whole page
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Magnetic Hard Disk
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Read/write head moves in and out to magnetise particles in two directions. Track is a concentric ring divided into sectors. Block is smallest unit of transfer
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Magnetic Tape
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Serial Access for backup & archive
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CD-ROM
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Read only
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CD-R
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Commercial write once disk
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CD-RW
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Can be read and written repeatedly. Laser is used to heat spot
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DVD-ROM
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Seven times more capacity than CD
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DVD-RAM
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Rewritable
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Secondary Storage
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Permanent storage to avoid re-entering data & programs
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Blu-ray Disk
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High Density optical disk
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USB Flash Drive
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NAND-type
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Universal Serial Bus
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Allows peripherals to be connected using a standard interface socket
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Memory Card
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Solid-state memory device with high capacity
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