Chapter 4 Discovering Computers Fundamentals

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Chapter 4Discovering Computers Fundamentals

• This is the System Unit (not the CPU)!
• The CPU is just one of many components inside of
  the System Unit.

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Review of Terms/Introduction

• Hardware the physical components of the
  computer
• Software the instructions telling the hardware
  to do a specific task
• Definition of Computer (Information Processing
  Cycle)
• Get Input
• PROCESS
• Output results
• Store information if desired
• This chapter is on the devices/equipment used for
  processing!

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Quick Mention of RAM

• RAM (memory) is used by computers to store
  information
• Any software/program that is running must be in
  RAM
• Basically, the instructions for those programs
  must be in RAM
• If you are playing both Solitaire and Minesweep,
  the main instructions for both of those games
  must be in RAM
• And dont forget, the instructions for the
  operating system are also in RAM, since the
  operating system is ALWAYS running!!!

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Motherboard

• The Motherboard (see photo in book) is the main
  part of the system unit
• Most devices in the system unit reside on,
  connect into, snap into, etc, the motherboard
• CPU
• Memory
• Expansion boards/cards (graphic and sound cards)
• Ports
• Bus
• For example, a mouse connects into a port, that
  is part of a card, that snaps into the
  motherboard.
• This chapter discusses the above in further detail

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CPU

• Interprets and carries out instructions
• A program/software is made up of a set of
  instructions (For example, in solitaire, the
  instructions could be deal cards, wait for
  person to move 1st card, etc)
• In reality, the instructions are much more
  detailed then what I listed.
• The CPU carries out the instructions one by one

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Parts of CPU Control unit

• One component of the CPU is the control unit.
  Its function is to
• FETCH one instruction from RAM/memory
• DECODE (or translate) instruction into something
  computer can understand
• EXECUTE the commands (or send instruction to the
  ALU to execute)
• STORE or save the results of that instruction
  back into RAM/memory

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More on Parts of CPUALU

• The ALU is the part of the CPU that actually
  executes the instructions.
• Specifically, it does the arithmetic and logic
  calculations

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More keywords relating to CPU

• Pipelining
• Pipelining is when the CPU fetches one
  instruction while the previous instruction is
  still being decoded
• Great explanation of this in book
• Most modern day CPUs all have this feature
• Obviously this means more instructions can be
  executed, which means your computer becomes faster

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Clock Speed of CPU

• Obviously, the faster the CPU the faster your
  computer
• NOTE CPU is one of many things that affect the
  speed of your computer. We will talk about other
  factors later
• Similar to how a clock ticks, the CPU clock also
  ticks
• During the duration of a tick, a certain number
  of instructions are executed
• The more ticks per second, the more instructions
  that can be executed per second
• The CPU clock is measured in MegaHertz (MHz)
• One million ticks per second

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More on MHz

• 1 MHz
• 1 million ticks per second
• 500 MHz
• 500 million ticks per second
• Remember, more ticks, mean more instructions can
  be executed
• Nowadays you can also measure CPUS in GHz
  (GigaHertz)
• 1 billion ticks per second

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Who makes CPUs/Processors

• Think of the Nissan Car company
• Nissan makes cars, but it makes various models
  Sentra (least powerful), Altima (more powerful),
  Maxima (even more powerful)
• Same with makers of Processors
• Intel, AMD, Motorola, are all companies/manufactur
  ers of processors
• Intel makes various models Celeron (for slower
  end PCs), Pentium, Xeon, and then Itanium (most
  powerful)

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More on Processor Manufacturers

• Back to the car analogy
• Even though Nissan Sentras and Nissan Maximas can
  both go 80 miles an hour, a Maxima is still more
  powerful
• Same with processors.
• For example, even though an Intel Celeron can be
  600MHz and Intel Pentium can be 600MHz, a Pentium
  is generally still more powerful
• Keep this in mind when buying computers!

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Data Representation

• Lets talk about how a computer stores
  information/data
• People communicate with words
• Analog using signals to represent data
• Computers communicate with 0s and 1s
• Digital using two electrical states (on-1 and
  off-0)

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More on Data Representation

• Think of Morse code
• To communicate with Morse code, you only have two
  options (long dashes/sounds and short
  dashes/sounds)
• The letter A could be a short dash followed by a
  long dash
• The letter N could be a long dash followed by a
  short dash
• There is a similar code for computers using 0s
  and 1s (or really, the absence of an electrical
  state and the presence of an electrical state)
• There is more than one code a computer can use
• ASCII, EBCDIC, UNICODE

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ASCII Codes

• The code used on most PCs and minicomputers is
  called the ASCII code
• EBCDIC code is used on mainframe computers
• A bit is a 0 or 1 (an off or on state)
• In the ASCII code, each character is represented
  by 8 bits
• The letter A is 01000001
• The letter N is 01001110
• Another term for 8 bits is 1 BYTE
• When you press the letter A on the keyboard, the
  signal is converted from the letter A to 01000001

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More on bits and bytes

• A bit is the smallest unit of data
• 8 bits is 1 byte (basically, 1 character/letter)
• 1 Kilobyte (KB) translates to approx. 1000 bytes
• 1 Megabyte (MB) approx. 1 million bytes
• 1 Terabyte (TB) approx. 1 trillion bytes
• KNOW THIS!!!

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Back to Memory

• Think of memory as the computers storage area
• There are three main types of memory that we will
  discuss
• RAM
• Cache (pronounced cash)
• ROM
• CMOS

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RAM Memory-volatile

• Random Access Memory (volatile)
• Everything that is running on your computer (the
  instructions) is stored in RAM.
• RAM is cleared if the computer is turned off
• When you first turn the computer on, the
  operating system (Windows 95/98) instructions are
  loaded into RAM
• If you start Solitaire, then the Solitaire
  instructions are loaded into RAM (with the
  operating system)
• Remember, the CPU fetches the instructions one
  by one from RAM
• When you turn off the computer, everything is
  cleared from RAM. When you boot up your computer
  the OS has to be copied back into RAM. The
  solitaire instructions will only be copied back
  into RAM if you decide to start it up again.

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Cache Memory

• Memory Cache or RAM Cache is a part of RAM that
  stores the most frequently used instructions/data
• Cache is much faster
• The CPU looks in the cache for data. If its
  there, it grabs it from the cache, which is much
  faster. If its not there, it gets it from RAM,
  which is a little slower
• Cache is faster, but more expensive, so you have
  a limited amount
• Keep this in mind when buying computers! More
  cache is more desirable!

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ROM Memory-nonvolatile

• Read-Only Memory (non-volatile)
• We will discuss this in more detail in a later
  chapter
• Contains instructions that are permanent, so to
  speak
• The contents of ROM are NOT lost when the
  computer is turned off it generally contains
  the same instructions
• These are instructions that are used when the
  computer is turned on
• More on this in chapter 8, for now, realize that
  these instructions are permanent, and this is a
  non-volatile memory.

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CMOS Memory - nonvolatile

• Pronounced (see-moss)
• Contains information about your computers
  configuration (type of keyboard, mouse, disks,
  current date, time, etc)
• Has a battery which allows the date and time to
  remain even when computer is off
• Contents of CMOS do not get wiped out when the
  computer is turned off, though it does get
  updated when you make changes to your computer
• For example when you add a new disk, etc

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Memory Slang

• Most people ask
• How much memory do you have?
• How fast is your memory?
• Generally they are referring to RAM.
• Just make sure you understand that there are
  other types of memory (RAM cache, ROM, CMOS, etc)

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Memory Performance

• Performance can be affected by your CPU speed
• The faster the CPU, the more instructions it can
  process, the faster your computer
• Access time of memory also affects speed
• The faster the CPU can access info from memory,
  the faster the CPU can start processing
• SRAM is one type of RAM
• DRAM is another type of RAM
• SRAM has faster access times than DRAM, but is
  more expensive
• Keep this in mind when you buy computers

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Memory Capacity

• Your computer has a limited amount of memory
• Memory capacity is measured in MBs.
• How many MBs of RAM (memory) do you have?
• 32MB is the minimum nowadays, but 64MB or 128MB
  is better
• Your computer has a certain number of slots
  available only for memory cards. If you need more
  memory, you can add a new card.
• Some memory cards are 32MB, some are 64Mb, etc
  Buy the card size you need, or can afford.
• Just make sure you have a free memory slot.

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If you plan to buy memory

• 1. Make sure the memory card you buy is
  compatible with the memory currently in your
  system
• Check the website for the PC manufacturer (Dell,
  IBM, etc)
• Look up your PC model
• It should say which memory cards are compatible
• 2. If you have more than one size (64MB card of
  memory and 32MB card of memory), put the larger
  card in the first slot. Just a little tip. Itll
  work either way, but this is the recommended way
  to get more out of your memory.

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How Memory Capacity Affects Performance

• The more memory, the more instructions your
  computer can hold at one time, the faster your
  computer
• If the instructions or data cannot fit in memory,
  it sometimes has to go look for it somewhere else
  (like the CD or disk drive which is much much
  slower)
• Sometimes if you run out of memory your computer
  can hang

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Expansion Cards and Expansion Slots

• Know some of these keywords
• Card or Expansion Card
• Video card
• Sound card
• NIC card
• Modem card
• Plug and Play

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Ports

• Plug in devices to a port
• Think of it as a wall socket on the computer
• Plug in a keyboard to a port
• Plug in a printer to a port
• Serial ports transmit data one bit at a time
• Slow, so used for keyboards, mouse, and modems
• Parallel ports transmit more than one bit at a
  time
• Faster, used for printers
• Other ports are listed in book (MIDI, USB, SCSI,
  IrDA)
• Ports are different shapes and sizes. Look at
  chart in book. Serial ports can have many shapes.
  Parallel ports can have many shapes. Make sure
  your cable matches the shape of the port!
• READ ABOUT USB ports!!!

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BUS

• How does one device on the computer communicate
  with another
• A keyboard plugs into a port, which is attached
  to the motherboard
• A disk is attached to the motherboard with a
  cable
• Memory snaps into the motherboard
• CPU resides on motherboard
• How does information from the keyboard get to the
  disk, get to memory, get to the CPU?

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More on BUSES

• The motherboard has channels called BUSES
• The bits travel on the buses from one device to
  another
• The faster the bus, the faster the data travels,
  the faster your computer

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Summary

• The CPU speed, memory capacity, memory speed,
  amount of cache, bus speed, etc can all affect
  your systems performance, though the CPU speed
  is the primary factor for a home PC.
• All programs that are currently running are
  stored in RAM. OS has to be loaded into RAM each
  time you start up the computer.
• The CPU processes each instruction one by one, by
  fetching them from RAM
• A computer stores data in bits (bytes, megabytes,
  etc)
• All items in the System Unit are ultimately
  connected to the Motherboard
• Buses on the motherboard allow the bits to travel
  from one device to another

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Practice

• How many bits in 1 byte?
• 8
• How many bits in 10 bytes?
• 8 10 80
• 40 bits equals how many bytes?
• 40 / 8 5 bytes
• How many bytes in 1KB?
• 1024 (or approx. 1000)\
• How many bytes in 1MB?
• Approx. 1 million

• Approx. how many bits in 1 KB?
• 1KB approx 1000 bytes
• 8 1000 8000 bits
• CPU speed is measured in
• Hz (MHz or GHz)
• Memory capacity is measured in
• Bytes (MB or GB)
• Intel makes what brands of processors? (which is
  slowest, fastest)
• AMD makes what brands of processors?

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The End