introduction to computers from chapters 1 & 2, computers- understanding technology 1bill pegram...
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Introduction to Computers
From Chapters 1 & 2, Computers- Understanding Technology
1Bill Pegram - August 30, 2009
What is a Computer
• Operates under control of a set of instructions, that is stored in its memory
• Accepts data from a user
• Manipulates the data according to the programmed instructions
• Produces the results
• Stores the results for future use
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Special-Purpose vs. General- Purpose Computers
• Special-purpose, or embedded computers, perform a few specific actions whereas general purpose computers can perform a wide range of actions
• Examples of special purpose computers would include chips in digital thermometer, microwave oven, digital camera, car
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Terminology
• Digital (0 vs. 1, on vs. off) vs. analog (pulses in continuous wave)
• Microcomputer or personal computer (intended to be operated by a single user)
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Computer System Hardware Components
• Motherboard - Central Processing Unit (CPU) (Chapter 2) and Memory (Chapter 2)
• Input Devices (Chapter 2)
• Output Devices (Chapter 3)
• Storage Devices (Chapter 3)
• Communications Devices
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Software
• System software (Chapter 4) - Operating system (e.g. Windows, MacIntosh)
• Utility software (e.g. file backup, virus protection)
• Application software (Chapter 5) – Office software, browsers, etc.
• Communications software
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Categories of Computers (p. 23)
• Personal computers
• Handheld computers
• Workstation
• Midrange server
• Large server or mainframe computer
• Supercomputer
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History of Computers Timeline
• Pages TI-A1-A14 following first chapter
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Input Devices
• Keyboard – alphanumeric & special function (some at fast food restaurant but touch screens increasing used)
• Touch screen – ATMs, airport checkin counters, kiosks, restaurant cashier, grocery store self-service checkout (e.g. Giant, Harris Teeter), VA DMV Written Test for Driver’s license, Apple iPhone, Windows 7 (successor to Vista)
• Mouse• Trackball – plastic sphere resting on rollers, often used
in laptop computers• Touchpads – you move the pointer by sliding your
finger across the surface of the pad
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Input Devices
• Operating systems such as Windows and Macintosh employ a graphical user interface (GUI – pronounced gooey) in which the user issues command by using a mouse to make selections
• With DOS (the previous operating system for IBM-compatible computers), users issued commands through typing on a keyboard
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Mouse Technology
• Mouse has used a rubber-coated ball on the bottom of the mouse; movement of the mouse on a surface results in rotation of the ball which is recorded by sensors in the mouse
• An optical mouse uses a light sensor instead of a ball to track movement
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Input Devices (cont.)
• Microphone (audio input)
• Joystick – computer games
• Graphics tablet and pen
• Optical scanner
• Bar code readers, magnetic card readers
• Digital cameras
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Input Devices (cont.)
• Digital video cameras – including retinal and thumb print scanners (e.g. preferred travellers at airports, thumb print scanners at tanning salons to prevent multiple visits within 24 hours)
• Nintendo Wii Remote and Platform
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Computer Representation of Data
• Bit (either 0 or 1)
• Byte - 8 bits
• ASCII (7 bit encoding) – PC’s
• EBCDIC (8 bit encoding) – large computers
• Unicode (16 bit) – used in newer operating systems such as Windows Vista and Macintosh OS X
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System Unit
• Power supply – converts from AC into DC and fan
• Bay or Storage bay – site where storage device can be installed
• Motherboard – thin sheet which has a number of components connected to it (see next slide)
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Motherboard
– CPU– System clock and battery– Slots for RAM chips– One or more read-only memory chips– Expansion slots– Ports for connecting input and output devices– Buses, which allow communication between
components in the computer
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Bays
• A bay is a site where a device such as a floppy disk drive or hard drive is installed
• An internal bay is concealed entirely within the computer case
• An exposed bay has an opening to the outside of a computer case
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Bays (cont.)
• The availability of empty bays used to be an important constraint on expanding the capabilities of a computer; much less important now due to the ability to connect external devices through USB ports (see later)
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Central Processing Unit
• Control unit – interprets program instructions and initiates action to carry them out – fetch and decode portion of machine or instruction cycle
• Arithmetic/logic unit (ALU) – execute part of cycle
• Registers – temporary storage locations that can be accessed much faster than locations outside of the CPU; instruction registers, data registers, storage registers
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CPU (cont.)
• System clock – generates pulses which synchronize activity within computer
• Clock speed is measured in hertz (pulses per second) – megahertz (MHz) (1 million/sec) and gigahertz (GHz) (1 billion/second) – chart p. 73
• One clock cycle equal to 2 clock ticks• Coprocessors – math, graphics,
cryptographic21Bill Pegram - August 30, 2009
Key Advances in Microprocessors
• Reduced instruction set computing (RISC)
• Pipelining – computer can begin executing another instruction as soon as previous instruction reaches next phase of machine cycle
• Closer circuits
• Better materials
• Parallel processing
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Key Advances in Microprocessors (cont.)
• Multithreading and hyperthreading – allows parallel processing
• Dual-core and multi-core processors
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Memory
• Random access memory (RAM) – each memory location has its own address so CPU can go directly to the instructions and data it needs
• Random access memory is reusable (new data or instructions can replace what was formerly there)
• Random access memory is volatile memory; only retains information while power is on
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Cache Memory
• Cache memory contains data and instructions recently used by processor; when CPU looks for data or instructions, it first looks in the cache
• Because there is often repeat use of data or instructions, this decreases time required to get the information
• A browser cache for images speeds up web surfing
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Read-only Memory (ROM)
• ROM contains instructions or data permanently there; does not depend on maintaining continuous power
• ROM contains BIOS (basic input/output system) program which is the program that boots or starts the computer when it is turned on
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Flash Memory
• Nonvolatile memory that can be erased and reused
• Used in many handheld computers and devices including flash drives (thumbnail drives) – significant increase in size and decrease in cost in last couple years
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Expansion and Ports
• Expansion boards – sound, video, graphics, modem, etc.
• Ports – external plug-in slot – serial or communications (COM) (one bit at a time)– Parallel (LPT)– traditionally used to connect printer– Video – connect monitor– USB (Universal Serial Bus) – can be used to connect
many type of devices
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Buses
• A bus is a pathway within a computer along which bits are transmitted
• Bus width refers to number of bits that can be transmitted at one time; e.g. 32-bit bus
• Expansion bus – interacts with RAM and low-speed devices
• Local bus – high speed peripherals and connects directly to CPU
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