Transcript CHAP01

Introduction to Computers,
Problem Solving, and
Programming
Chapter 1
1.1 Overview of Computers
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Computer - “A device for counting or
computing”
Dr. John Atanasoff - 1st computer.
ENIAC 1946 at U of Penn
Dr. John Von Neumann - Princeton
– Stored program concept
– Memory rather than wires and switches.
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Computing History
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Overview of Computers
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Von Neumann architecture basis for today's
computers
VLSI Technology made computers
affordable, small and available to the public
How programming has changed over time
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1.2 Computer Hardware
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Every computer is organized roughly into
six parts
– CPU - central processing unit
• Where decisions are made, computations are
performed, and input/output requests are delegated
– Main Memory
• Stores information being processed by the CPU
– Secondary Memory
• Stores data and programs
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Computer Hardware
– Input devices
• Allows people to supply information to computers
– Output devices
• Allows people to receive information from
computers
– Network connection
• Modems / Ethernet interface
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Computer Components
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Main Memory
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Address
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Contents
0
1
1024
-27.2
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354
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.005
75.62
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Main Memory
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Stores
– programs
– data
– results
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Types
– RAM
– ROM
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Secondary Memory & Storage
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Semi permanent data-storage capability
– Tape or Disk
– Hard disk
– CD ROM
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Secondary memory has much more storage
capacity
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CPU
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“Brains” of the computer
– Arithmetic calculations are performed using the
Arithmetic/Logical Unit or ALU
– Control unit decodes and executes instructions
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Arithmetic operations are performed using
binary number system
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CPU
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Fundamental building block is a switch
– Switches are made from ultrasmall transistors
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Examples
– The Pentium ® processor contains about three
million transistors
– The Pentium Pro ® has about 5.5 million
transistors
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Input / Output Devices
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Accessories that allow computer to perform
specific tasks
– Receiving information for processing
– Return the results of processing
– Store information
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Common input and output devices
– Printer
– Keyboard
Joystick
Monitor
CD-ROM
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Computer Networks
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LAN - Local area network
– Organizational
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WAN - Wide area network
– Internet
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World Wide Web
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Introduced 1989
Developed by CERN
– European Laboratory for Particle Physics
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Web browser
– GUI
– Netscape
– IE
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1.3 Computer Software
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Application software
– Programs designed to perform specific tasks
that are transparent to the user
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System software
– Programs that support the execution and
development of other programs
– Two major types
• Operating systems
• Translation systems
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Application Software
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Application software is the software that
has made using computers indispensable
and popular
Common application software
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Word processors
Desktop publishing programs
Spreadsheets
Presentation managers
Drawing programs
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Operating System
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Controls and manages the computing resources
Important services that an operating system provides
– File system
– Commands that allow for manipulation of the file
system
– Ability to perform input and output on a variety of
devices
– Management of the running systems
Examples
– MSDOS ®, Windows ®, Unix ®
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Programming Languages
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Machine Language
– “Native tongue” of the computer
– Binary 0s and 1s that specify what to do
• 0010 0000 0000 0100
• 1000 0000 0000 0101
• 0011 0000 0000 0110
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High - Level Languages
– Resemble human language (C++, C, Pascal)
• cost = price + tax;
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Programming Languages
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Language Standard
– Syntax (grammatical form) (rules)
– Portable
• programs used without modification
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Source Program
Object Program
Executable Program
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Object Oriented Programming
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OOP derived from C
Bjarne Stroustrup
Popular because of reuse
– Classes
– Objects
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Organized in a Hierarchy
– Super Classes
– Sub Classes
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OO Programming and
Structured Programming
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Object-oriented design and programming
supports good software engineering
Object-oriented design promotes thinking
about software in a way that models the real
world
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OO Programming and
Structured Programming
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Algorithms are the basis for the procedural
sections (Structured Programs)
– Highly structured
– Top-down design
– Step-wise refinement
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Object Oriented Design
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Abstraction
– Extract the relevant properties of an object
while ignoring inessential details
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Encapsulation
– Breaking down an object into parts, hiding and
protecting its essential information, and
supplying an interface to modify the
information in a controlled and useful manner
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Object Oriented Design
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Modularity
– Dividing an object into smaller pieces or
modules such that the object is easier to
understand and manipulate
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Hierarchy
– Ranking or ordering of objects based on some
relationship between them
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Abstraction
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Process of extracting only the relevant
properties of an object
Extracted properties define a view of the
object
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Abstraction
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Car dealer views a car from selling features
standpoint
– Price, warranty, color, etc.
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Mechanic views a car from systems
maintenance standpoint
– Oil, oil filter, spark plugs, etc.
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Encapsulation
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Breaking down an object into parts, hiding
and protecting its essential information, and
supplying an interface to modify the
information in a controlled and useful
manner
By hiding the information its representation
and content can be changed without
affecting other parts of the system
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Encapsulation
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Example - car radio
– Controlled by switches and knobs
– The details of how it works is hidden
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Modularity
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Dividing an object so that the object holds
useful information and it is easier to
understand
Most complex systems are modular
– Cooling System
– Ignition System
– Fuel System
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Modularity
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Example - Automobile can be decomposed
into subsystems
– Cooling system
• Radiator
• Thermostat
• Water pump
– Ignition system
• Battery
• Starter
• Spark plugs
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Hierarchy
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Ranking or ordering of objects based on
some relationship between them
Hierarchies facilitate understanding
complex organizations and systems
– Example - a company hierarchy helps
employees understand the structure of their
company and their positions
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OO Classes
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Later we will use data abstractions
– C++ language
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Will apply OO techniques
– Structured Programming
– Object Oriented Programming
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Model our own objects or abstractions
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1.4 Processing a High-Level
Language Program
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Set of programs used to develop software
A key component of a is a translator
Types of translators
– Compiler
– Linker
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Examples
– g++, Borland C++ ®, Microsoft Visual C++ ®
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Processing a Program
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Editor used to enter the program
– Source program (file.cpp)
– UNIX vi text editor
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Compiler translates the source program
– Displays syntax errors (not descriptive)
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Linker/Loader to combine object file with
other object files
– Executable program
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Processing a Program
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Major activities
– Editing
– Compiling
– Linking with pre-compiled files
• Object files
• Library modules
– Loading and executing
– Viewing the behavior of the program
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Process Cycle
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1.5 Software Development
Method
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Problem Analysis - (Correct Problem)
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Identify data objects
Goal to model properties
Determine Input / Output data
Constraints on the problem
Design
– Decompose into smaller problems
– Top-down design (divide and conquer)
– Develop Algorithm (Desk check)
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Software Development
Method
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Implementation
– Writing the algorithm
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Testing
– Verify the program meets requirements
– System and Unit test
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Documentation
– Key part in the development process
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Software Development
Method
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Software engineering
– Area of computer science concerned with
building large software systems
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Challenge
– Tremendous advances in hardware have not
been accompanied by comparable advances in
software
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Software Engineering Goals
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Reliability
– An unreliable life-critical system can be fatal
Understandability
– Future development becomes very difficult if
software is hard to understand
Cost Effectiveness
– Cost to develop and maintain should not exceed
profit
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Software Engineering Goals
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Adaptability
– System that is adaptive is easier to alter and
expand
Reusability
– Improves reliability and maintainability, and
reduces development costs
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1.6 Applying the Software
Development Method
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Case Study:
Kilometers
Converting Miles to
– Problem Your summer surveying job requires
you to study some maps that give distances in
kilometers and some that use miles. You and
your coworkers prefer to deal in metric
measurements. Write a program that performs
the necessary conversion.
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Applying the Software
Development Method
– Analysis The first step in solving this problem
is to determine what you are asked to do. You
must convert from one system of measurement
to another, but are you supposed to convert
from kilometers to miles, or vice versa? The
problem states that you prefer to deal in metric
measurements, so you must convert distance
measurements in miles to kilometers.
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Applying the Software
Development Method
– Design The next step is to formulate the
algorithm that solves the problem. Begin by
listing the three major steps, or sub problems,
of the algorithm.
– Implementation To implement the solution,
you must write the algorithm as a C++
program.
– Testing How do you know the sample run is
correct?
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1.7 Professional Ethics for
Computer Programmers
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Privacy and Misuse of Data
Computer Hacking
Plagiarism and Software Piracy
Misuse of a Computer Resource
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