Revision

1
Revision

• Semester 2, Week 11

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2008 Exam

• Summer Exam,
• Monday 12 May, 1.30pm 4.30pm
• 8 Questions (with parts a, b and c), choose any 5
• 20 each

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The Topics

• A systems overview
• Representing information
• Number bases
• Hardware memory and buses
• Boolean algebra
• Logic gates
• Flip-flops, latches, internal circuits
• Assembly language

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The Topics (2)

• Software
• Input devices
• Output devices
• Storage devices
• Networks
• Viruses and diagnostic software
• Computers in organisations/New technology

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Sample Notes from the Systems Overview

• Is a system a configuration? They certainly seem
  to have a lot of similarities.
• A configuration is defined in the dictionary as
  an arrangement of parts. A system is defined as
  a set of connected parts. The inference is that a
  system functions, somehow, where a configuration
  does not, necessarily.
• There are hardware configurations
• There are software configurations
• There are system configurations
• In computer terms a configuration is the
  description of what hardware and/or software
  exists whereas the system description is more
  general.

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Sample Notes from the Systems Overview (2)

• Boot Process at Startup
• When you switch on your personal computer (PC)
  you will often see a black screen with prompts
  that scroll and disappear as the machine prepares
  for the operating system.
• These are startup routines that are, essentially,
  instructions to the hardware system to find and
  run other instruction files that motivate the
  operating systems.

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Sample Notes from the Systems Overview (3)

• In the early days of computers in industry the
  machines had a program called the bootstrap
  loader by which the machine pulled itself up by
  its bootstraps.
• This enduring analogy has provided the name for
  the PCs startup routines, which get the whole
  operating system running on the computer.

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Sample Notes from the Systems Overview (4)

• Operating Systems at Startup
• The operating system is a collection of system
  software routines which control the hardware
  resources of the system and the flow of
  information in and out of the computer.
• The operating system also supports application
  programs by, for example, handling input/output
  devices and routines that the application needs.

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Sample Notes from the Systems Overview (5)

• Program development and maintenance utilities
  might include
• Assemblers
• Linkers/Loaders
• Compilers
• Editors
• Debuggers
• Utilities (e.g. transfer programs for
  data-to-peripheral devices)

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Sample Notes from Representing Information

• Five types of information the computer commonly
  manipulates
• Numeric
• Character
• Visual
• Audio
• Instructional
• First, the information must be transformed
  (converted) into an acceptable representation
  that the computer will accept.

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Sample Notes from Representing Information (2)

• A picture must be transformed into numeric form
  before it can be stored or manipulated by the
  computer.
• Each picture is subdivided into a grid of squares
  called pixels (picture elements).
• An image on paper can be converted into pixels
  using a scanner.
• Digital cameras store their images as digital
  images, i.e. the picture is already stored in the
  cameras memory as pixels.

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Sample Notes from Representing Information (3)

• A picture with only black and white pixels
• 1 represents black.
• 0 represents white.
• Colours
• Red, Green, Blue (RGB)
• The primary light colours use three values per
  pixel.
• One number is used for each of the amounts of
  Red, Green and Blue on the computer screen.

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Sample Notes from Representing Information (4)

• Instructions are described as being imperative in
  the sense that they command action - or, at
  least, advise action. In most aspects of life
• Instructions must be clearly understood by its
  intended receiver.
• The information needed to process the instruction
  must be readily available. Examples
• Setting a microwave oven.
• Following a cooking recipe. (Consider that a
  recipe has a method (instructions) and
  ingredients (data)).
• It is similar with computer programs. Programs
  are all (essentially) sequential instructions and
  need to be structured with 'complete
  information'.

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Sample Notes from Number Bases

• Negative numbers are represented, in binary, by
  Two's Complement.
• To decrement in binary you find the Two's
  Complement for the number you wish to decrement
  by (or subtract) and ADD it to the number from
  which the subtraction must be made. This is the
  most efficient and reliable way to reduce the
  value of numbers (or to create a new number based
  on subtraction) when operating in binary number
  form.
• Here is an example of Two's Complement (or 2's
  complement).

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Sample Notes from Number Bases (2)

• To convert -1210 to 2s complement using 6 bits
• Decide upon the number of bits n (6).
• Find the binary representation of the ve value
  in n-bits (0011002).
• Flip all the bits (change 1s to 0s and vice
  versa) (1100112).
• Add 1 (1101002)
• -1210 1101002

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Sample Notes from Number Bases (3)

• Suppose that we group the binary digits into
  fours. Then this might be written
• 9,58710 00100101011100112
• 958710 257316
• This is called the Hexadecimal representation.
• Hex (short for "hexadecimal") is very similar to
  octal in its relationship to binary. It just
  takes one more binary column to account for one
  hex column.

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Sample Notes from Boolean Algebra

• Boolean algebra is defined as a closed algebraic
  system containing a set K of two or more elements
  and the two operators, and .
• 0 is the identity element for the operation.
• 1 is the identity element for the operation.
• Four properties
• The commutative property
• The associative property
• The distributive property
• The complement

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Sample Notes from Logic Gates

• A computer system's clock speed is measured as a
  frequency, usually expressed as a number of
  cycles per second.
• A crystal oscillator controls clock speeds, using
  a sliver of quartz in a small tin container. As
  voltage is applied to the quartz, it begins to
  vibrate (oscillate) at a harmonic rate. The
  oscillations emanate from the crystal in the form
  of a current that alternates at the harmonic rate
  of the crystal. This current is the clock signal.
  A computer system runs millions of these cycles
  per second. Speed is measured in megahertz (MHz).
  (1 Hz 1 cycle per second.)

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Sample Notes from Logic Gates (2)

• If a CPU is described as having a 'clock speed of
  2.66 GigaHertz' then one can assume that a square
  wave can be detected, from the quartz crystal on
  the chip, 2,660,000,000 times in a second, when
  electricity is passed through the crystal.
  (Around two billion, six hundred and sixty
  million times in a second.)
• The internal logic gates can be opened and
  closed, by the wave signal, up to 2.66 billion
  times per second.

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Sample Notes from Assembly Language

• Because it is easier to write a program by
  subdividing into subprograms or subroutines, most
  Assemblers have been written to assemble
  subroutines or subprograms and then combine them
  into a single entity.
• The output of the Assembler is in binary-symbolic
  or semi-compiled form and it is converted into
  'absolute' machine code by a loader.

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Sample Notes from Assembly Language (2)

• An Assembly Language instruction that generates
  more than one machine code instruction is called
  a macro instruction.
• In Assembler, a macro definition defines how to
  expand a single language statement or computer
  instruction into a number of instructions.
• A macro incorporates into the user's program a
  procedure that would carry out the same process
  in any other program that included it.

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Sample Notes from Assembly Language (3)

• For example, the IBM macro, DUMP causes the CPU
  to print out, line by line, the contents of every
  location in memory and then perform all the
  operations necessary to terminate the program
  currently in the computer's memory.
• A macro of this type is a complicated operation
  one Assembly language instruction has been
  converted into many machine code instructions.

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Sample Notes from Assembly Language (4)

• Instruction mnemonics are used by many
  assemblers.
• Each listed instruction has one or two examples
  but there may be several more examples of each
  type of instruction.
• In actual programs there will most often be
  numbers or addresses pertaining to the mnemonic
  that follow the three- or four-letter
  instruction.Also, there may be variations on the
  instruction. An example of that is MOV since this
  instruction does not need parameters when it
  appears as MOVS.

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Sample Notes from Software

• Resource management is the part of operating
  system that manages the hardware and networking
  resources of a computer system with CPU, memory,
  secondary storage device, telecommunications, and
  input/output peripherals.
• File management is the part of the operating
  system that controls the creation, deletion, and
  access of files of data and programs.
• Task management is the part of the operating
  system that manages the accomplishment of
  computing tasks of the end users. Multitasking is
  a major feature of task management. It allows for
  several tasks to be performed by the processor -
  seemingly simultaneously.

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Sample Notes from Software (2)

• Object-oriented languages (O-O) combine data
  elements and the procedures that will be
  performed upon them into objects.
• For example, an object could be data about a bank
  account and the procedures performed on it such
  as interest calculations.
• Object-oriented languages are the most widely
  used software development languages today.

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Sample Notes from Software (3)

• Web Languages
• HTML
• Hypertext markup Language
• XML
• Extensible Markup Language
• Java
• This is an object-oriented programming language
  that is simple, secure and platform independent.

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Sample Notes from Storage Devices

• Hardware Data Storage Types
• Magnetic disk
• Floppy disk
• Zip disk
• Hard disk
• Disk pack

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Sample Notes from Storage Devices (2)

• Hardware Data Storage Types
• Solid state memory
• SD-RAM type
• Flash type
• SDRAM (Synchronous Dynamic Random Access Memory)
  various kinds of dynamic Random Access Memory
  that are synchronised with the optimal clock
  speed of the microprocessor.
• Flash memory (or Flash RAM") is a type of
  constantly-powered nonvolatile memory that can be
  erased and reprogrammed in blocks of memory
  (rather than bytes).

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Sample Notes from Networks

• There are usually seven layers to many network
  communications in terms of protocols
• Physical layer
• Data link layer
• Network layer
• Transport layer
• Session layer
• Presentation layer
• Application layer

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Sample Notes from Computers in Organisations

• Information Systems for Management
• Strategic information systems for senior
  management
• Executive information systems,
• Decision support systems.
• Tactical information systems for middle
  management
• Project management tools,
• Forecasting (database).

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Sample Notes from Computers in Organisations (2)

• Knowledge information systems for knowledge
  workers
• Computer aided design (CAD),
• Computer aided manufacturing (CAM),
• Administrative systems.
• Operational systems for production workers
• Applications (Word, Excel)
• Robotics
• Input-output systems

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Sample Notes from New Technology

• Place two or more processor circuits on one IC
  (integrated circuit) or two or more individual
  processors to work together - and you have a
  multicore (or multi-core) architecture.
• Multi-core more than one core
• Dual-core two CPU cores on one IC or two
  separate ICs
• Multi-chip module an alternative name for
  two or more separate ICs
• Double core or twin core - alternative names
  for two separate ICs
• Quad-core four CPU cores on one IC or two
  separate ICs

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Sample Notes from New Technology (2)

• There are a number of Internet browsers for the
  user to choose from.
• Four proprietary Internet browsers are
• Firefox
• Netscape Navigator
• Internet Explorer
• Opera

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A Past Paper Question and Answer

• Question 4 (Summer exam, 2006)
• Show how addition and multiplication work in
  Boolean arithmetic.

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Question 4 (a) Sample Answer

• Solution
• Boolean arithmetic
• With two states for input and output, it turns
  out that
• Addition WILL work,
• Subtraction WILL NOT work,
• Multiplication WILL work,
• Division WILL NOT work.
• Addition works as OR
• 0 0 0
• 0 1 1
• 1 0 1
• 1 1 1
• 1 1 can not be 0 nor can it be 2, so Boolean
  logic means it has to be 1.

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Question 4 (a) Sample Answer

• Multiplication works as AND
• 0 x 0 0
• 0 x 1 0
• 1 x 0 0
• 1 x 1 1
• A B reads, A OR B,
• A x B reads A AND B but since, in mathematics,
  generally, a dot () is used to show
  multiplication or nothing at all the notation
  might be AB or AB might appear for A AND B.
• (10 marks)

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Question 4 (b)

• Describe, briefly and in general terms, how logic
  gates allow data movement within or to/from a
  Central Processing Unit.

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Question 4 (b) Sample Answer

• Solution
• Logic gates are the fundamental building blocks
  of all digital logic circuits they are
  switching circuits that perform certain simple
  operations on binary signals.
• These operations are chosen to facilitate the
  implementation of functions such as changing 1s
  to 0s or 0s to 1, filtering 1s only or 0s only,
  checking for combinations of 1s and/or 0s (A few
  others.)
• These allow for bits and bytes to be shifted
  through circuits and/or converted in the CPU.
• Those shifts and conversions are the fundamental
  elements of computation. All action associated
  with components like the BIOS and the CPU need to
  use logic and algebra.
• (3 marks)

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Question 4 (c)

• Describe De Morgans theorems of Boolean logic.

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Question 4 (c) Sample Answer

• Solution The mathematician, De Morgan had a
  theorem that showed that one gate could be made
  to work like another by inverting inputs and
  outputs. There are two parts to the theorem the
  complement of two or more variables ANDed is
  equivalent to the OR of the complements of the
  individual variables.
• ___ __ __
• (A.B) A B
• (NOT A AND B NOT A OR NOT B)
• The complement of two or more variables ORed
  together is equivalent to the AND of the
  complements of the individual variables.
• ____ __ __
• (AB) A . B
• (NOT A OR B NOT A AND NOT B)
• (7 marks)

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End of Computer Technology

• Thats it!Good luck with the exam!
• It has been very enjoyable to take this subject
  with you this year.
• Art