Five Key Computer Components

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Five Key Computer Components

• Central Processing Unit
• Memory
• Input/Output (I/O) Devices
• Disk Storage
• Programs

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Central Processing Unit

• Executes instructions (programs)
• To do this the CPU can
• read/write information in memory
• recognize difference between instruction and data
• control I/O devices

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Memory

• Also known as Primary Storage
• Provides temporary storage of programs and data
• Can be accessed directly by CPU or through I/O
  devices

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Input/Output Devices

• Mouse
• Keyboard
• Video Display
• Printer
• Modem
• Communication Lines (Networks)

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Disk Storage

• Also known as secondary storage
• Provides permanent (non-volatile) storage of
  programs or data.

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Programs

• System Software
• BIOS- Basis Input/Output Services (ROM)
• Operating System - DOS, Windows, Unix
• Application Software
• Word Processors
• Database
• etc

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More PC Hardware Terms

• serial - all information goes one bit at a time
  over the same wire.
• parallel - bits go over many wires running side
  by side.
• clock - sends pulses to synchronize the CPU and
  other hardware.
• MHz - megahertz, one million clock pulses per
  second.

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Main Hardware Components

• System Unit
• Display
• Keyboard
• Mouse

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System Unit

• System Board (Mother board)
• Central Processing Unit (CPU)
• Memory (RAM - Random Access Memory)
• ROM (Read-only Memory)
• Expansion Slots
• Math Co-processor
• 486 and 586 CPU has integrated Math co-processor.

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PC Expansion Bus

• Connects CPU to circuit boards which control
  devices such as disk drives, printer, display,
  modems, etc

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ISA Industry Standard Arch.

• Commonly known as AT bus.
• 8 or 16 bit data bus, 98-pin expansion connector.
• Can access up to 16 MB of memory.
• Common and cheap but very slow (8Mhz).

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MCA

• Micro Channel Architecture
• Designed by IBM to replace ISA in PS/2 system.
• not compatible with ISA bus boards.
• 16 and 32 bit versions.
• Not seen much anymore.

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EISA

• Extended Industry Standard Architecture
• designed by Compaq and other clone companies as
  alternative to MCA
• Allows use of ISA bus boards in new computers.

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Local Bus

• Communicates at system speed
• Memory, display, disk drives all can use local
  bus.
• Provides 32 or 64 bit data access.

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Local Bus Standards

• VESA VL Bus - (Video Electronics Standards
  Association)
• First to gain popularity
• 32 bit bus running at 33 MHz can handle up to 107
  Mbytes/second
• PCI (Peripheral Component Interconnect)
• 32 bit bus running at 33 MHz can handle up to 132
  Mbytes/second
• faster and more easily expanded than VESA bus

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SCSI

• pronounced scuzzy
• used with printers, hard disks, tape drives.
• excellent for high-speed data transfer in
  multi-user systems or file servers.
• Can handle up to 7 devices on one adaptor card.

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Gates

• Fundamental building block of all digital logic
  circuits.
• Logic functions are implemented by the
  interconnection of gates.
• An electronic circuit that produces an output
  signal that is a simple Boolean operation on the
  input signals.
• The basic gates are AND, OR, NOT, NAND, NOR.
• Basic gates have either one or two input lines
  and a single output line.
• When the signals on the input lines change, the
  correct output signal is generated by the gate,
  almost simultaneously, delayed only by the
  propagation time of the signals through the gate
  (called gate delay).

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Boolean Operations
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Multiplexers

• A multiplexer connects multiple inputs to a
  single output. At any given time, one of the
  inputs is selected and is passed directly to the
  output. Multiplexers are used in digital
  circuits to control signal and data routing.
  Shown below is a block diagram of a 4-to-1
  multiplexer. There are four input lines labeled
  D0, D1, D2, and D3 of which one is selected to
  provide the output signal F. To select one of
  the four input signals, a 2-bit selection code is
  required and this is implemented as the two
  select lines labeled S1, and S2.

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Multiplexers
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Decoders

• A decoder is a combinational circuit which has a
  number of output lines, of which only one is
  valid (asserted) at any time, dependent upon the
  pattern on the input lines. In general, a
  decoder has n input lines and 2n output lines.
  Decoders are heavily used in digital computers
  for address decoding.

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Decoders