Essential Computer Concepts Systems Architecture

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 Essential Computer Concepts - Systems
Architecture -

• 19 JANUARY 06

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What is a computer and what does it do?

• (Refer to Chapter 3 in the text)A computer is a
  programmable electronic device that accepts data
  and performs operations on that data.
• Inputentering data into the computer.
• Processingperforming operations on the data.
• Outputpresenting the results.
• Storagesaving data, programs, or output for
  future use.

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PROCESSING CYCLE
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Understanding Data Representation

• Machine language is the binary-based code used to
  represent program instructions
• Machine code is composed only of the two binary
  digits 0 and 1. Computer data is digital and
  represented by microscopic switches that are off
  or on. The "words" of a machine language are
  called instructions each of these gives a basic
  command to the CPU. A program is just a long list
  of instructions that are executed by a CPU.The
  computer can only recognize off and on. These
  switches are represented as binary digits or bits
  for short. 
• Off0 On1

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VISUAL BINARY
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Numbering Systems

• Unless you're attempting to understand low level
  programming, learning binary provides you with
  two things
• comprehension of how your computer stores
  information, with a better understanding of bits,
  bytes, kilobytes, etc...
• an easy method of converting between decimal and
  hexidecimal. You don't have to learn to count in
  hexidecimal either, but I/O addresses and memory
  addresses are given in hex and sometimes you can
  resolve device conflicts by being able to tell if
  addresses overlap.

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AN ELEMENTARY METHOD

• Decimal (base 10)The decimal numbering system is
  the system we all use in our everyday work. It
  consists of 10 digits (hence the name decimal).
  The digits, from smallest to largest are0, 1,
  2, 3, 4, 5, 6, 7, 8, 9.
• Now, any number can be broken down into columns.
  From right to left, the first column is the 1's
  column, then the 10's column, then the 100's,
  then the 1000's, etc..Let's look at the number
  137
• 0 X 1000 0 (0 thousands)1 X 100 100 (1
  hundreds)3 X 10 30 (3 tens)7 X 1 7 (7 ones)
• 0100 30 7 137

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ON YOUR OWN

• OK, lets try the number 770 X 1000 0 (0
  thousands)0 X 100 0 (0 hundreds)7 X 10 70
  (7 tens)7 X 1 7 (7 ones)
• 0070 7 77

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Binary (base 2)

• Your computer works using the binary numbering
  system. This is because a computer can only
  recognize two states, the presence of an
  electrical charge or the absence of an electrical
  charge. In other words, on or off.
• The binary numbering system is ideal for
  representing these two states because it consists
  of only two digits. The digits, from smallest to
  largest are0, 1.
• 0 represents the absence of an electrical charge
  or 'off'.1 represents the presence of an
  electrical charge or 'on'. (Now you can
  understand why the power switch on your computer
  is labeled as O/1).

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TABLE IT

• Any number can be broken down into columns. Each
  column is a placeholder. Using the binary
  numbering system, from right to left, the first
  column is the 1's column, then the 2's column,
  then the 4's, then the 8's, then the 16's column,
  then the 32's column, etc..Let's look at the
  number 137 again

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137 128 (R,9) 9 8 (R,1) 1-1 DONE!
Try the number 77 on your own!
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Binary Digit

• A single digit (0 or 1) is called a 'bit' (binary
  digit).
• The table on the previous slide contains 8 bits.
  Each column can contain either a 1 or a 0 (
  'cause there is only 2 digits in the binary
  numbering system). So, as you can see, it takes 8
  bits to represent the decimal number 137.

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8 bits 1 byte

• Any character that you type (including spaces),
  and any character you can see on your screen,
  takes 8 bits for your computer to produce. Eight
  bits associated together are called a 'byte'. A
  byte is the real building block of computer
  information. This can form a single character. A
  character can be a number, letter, or symbol. The
  amount of information a device can store is
  measured in bytes. Because of this, most numbers
  and sizes reported by the computer are evenly
  divisible by 8.Multiple bytes associated
  together are often called a 'word'.

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• 8 bits 1 byte1024 bytes 1 kilobyte (Kb)1024
  kilobytes 1 megabyte (Mb)
  (1,048,576 characters or bytes)1024 megabytes
  1 gigabyte (Gb)
• These numbers are often rounded off for ease of
  calculation.You might see 1 megabyte represented
  as a million bytes (1,000,000 characters), or
  1000 kilobytes.

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Hexidecimal (base 16)

• Remember, that eight bits make a byte, and that
  it takes eight bits to store a single character
  in the computer. 1024 bytes make a kilobyte and
  1024 is divisible by eight. Seems like the magic
  number for computers is eight. The thing is, even
  relatively low binary numbers can be long and
  cumbersome.
• The hexidecimal numbering system consists of
  sixteen digits. The digits, from smallest to
  largest are0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B,
  C, D, E, F.

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• Once again, any number can be broken down into
  columns. Each column is a placeholder. Using the
  hexidecimal numbering system, from right to left,
  the first column is the 1's column, then the 16's
  column, then the 256's, then the 4096's, then the
  65536's column, etc.. Because you multiply the
  number in each previous column by 16, you can see
  that the numbers get very large and scary very
  quickly.

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Decimal 137 89h (Hexidecimal)

• Here's an easier way. Any group of 4 binary
  digits can represent up to sixteen values. A
  single hexidecimal digit can stand for any one of
  the 16 values that can be represented by any 4
  bit binary number. In other words, break any
  binary number into groups of 4 bits. Use a chart
  (or if your memory is good you can use that) to
  find the proper hex number that represents those
  four bits.

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Take home Practice for Tues Review
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ANSWER!
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 ASCII

• American Standard Code for Information Exchange -
  used to represent text data.
• Fixed-length codes that can represent any single
  character of data as a string of eight bits.
• Understand the need for Hex - Binary
  representation alone would be too cumbersome.

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ASCII

• A series of eight bits is called a byte and each
  byte represents one character for programming
  purposes.
• (Example)  0100 0001 the letter A --- or 41h or
  0x41 in hex

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Size/ Capacities

• Computer memory and storage capacities are
  represented in megabytes Graphics are byte
  intensive.  
• 1 , 0   1 bit
• 4 bits 1 hex character (nibble)
• 8 bits 1 byte
• 210 1,024 bytes or 1 Kilobyte (thousand)
• 220 1,048,576 bytes or 1 Megabyte (million)
• 230 1,073,741,824 or 1 Gigabyte (billion)
• 240 1,099,511,627,776 bytes or 1 Terabyte
  (trillion)
• Defining Units of Measure Computer jargon
  includes various terms for measuring access
  speeds and data storage. You may seem confused at
  first by all the new terms megabytes, kilobytes,
  milliseconds, megahertz.

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A Look Inside
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!!!

• The two most important pieces of processing
  hardware are the CPU Processor and RAM

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Central Processing Unit

• Microprocessor (CPU) Integrated circuit, also
  called a chip. The Brain of the computer
  Composed of
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• ALU Arithmetic Logic Unit
• Processor Controller
• High speed calculator Intel is the most popular
  chip  
• Categorized by model numbers Higher model
  numbernewer/faster chip  
• Speed of CPU is determined by clock speed Higher
  the clock speed, faster the computer Speed is
  measured in megahertz (MHz) Megahertz Clock
  Speed of the processor (100 MHz 100 million
  cycles/second).

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CPU Cont
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Memory or RAM

• Next most critical element of a computer system.
  RAM receives and temporarily stores data and
  program instructions from the CPU This data bank
  communicates with the CPU, constantly exchanging
  information and constantly changing as long as
  the computer is on  
• RAM is an active, electronic state. Power offRAM
  empty. Data gone, unless it was stored.
• When booting, operating system loads instructions
  into RAM  
• Random Access Memory (RAM) is the workhorse
  behind the performance of your computer. Working
  as a foot soldier for your processor, RAM
  temporarily stores information from your
  operating system, applications, and data in
  current use. This gives your processor easy
  access to the critical information that makes
  your programs run. The amount of RAM you have
  determines how many programs can be executed at
  one time and how much data can be readily
  available to a program. It also determines how
  quickly your applications perform and how many
  applications you can easily toggle between at one
  time. Simply put, the more RAM you have, the more
  programs you can run smoothly and simultaneously.
  
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• To determine how much RAM you need, factor in the
  demands of the applications you want to run
  simultaneously as well as the operating system
  (256MB of RAM is recommended by Microsoft as
  minimum for operation of Windows) Then keep in
  mind that you'll inevitably add new applications
  and create new files, and add accordingly.

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Types of RAM

• DRAM (Dynamic RAM) This is the most common type
  of computer memory. DRAM needs refreshing and is
  refreshed hundreds of times each second in order
  to retain data. During recharging it cannot be
  accessed by the CPS
• SRAM (Static RAM) SRAM is approximately 5 times
  faster (and twice as expensive, as DRAM). It does
  not have to be constantly refreshed. Because of
  its lower cost and smaller size, DRAM is
  preferred for the main memory, while SRAM is used
  primarily for cache memory.
• SDRAM (synchronous dynamic RAM) is the standard
  memory offering in the PC industry and is faster
  than DRAM because it's synchronized to the system
  clock. . It is designed for mainstream home and
  business applications, email, and basic audio and
  video streaming. It provides single-channel
  memory and is available on our mainstream and
  value desktop system.
• DDR SDRAM (double data rate synchronous dynamic
  RAM) takes all the features of ordinary SDRAM and
  increases the frequency bandwidth to improve
  system performance and speed.
• RDRAM (Rambus dynamic RAM) is able to load a new
  stream of data before the previous stream has
  completed, resulting in faster access speeds. The
  RDRAM memory features dual-channel processing
  which doubles data throughput to further enhance
  performance. This type of memory is optimized for
  high-end multimedia tasks involving video and
  audio. Dual Channel RDRAM is shipped on our
  performance desktop systems powered by Pentium 4
  processors
• VRAM Memory designed for storing the image to be
  displayed.
• CACHE RAM is a small block of high-speed memory
  located between the Processor and main memory and
  is used to store frequently requested data and
  instructions. When the processor requests data,
  it will check in the cache first

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ROM

• Read Only Memory
• CPU can read these commands, but cannot write to
  these storage locations. Burned into the CMOS,
  used for the boot process.

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Understanding the relationship of RAM and CPU
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