Cosc 1P02

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Cosc 1P02

• Week 1 Lecture slides

"If a man does his best, what else is
there? General George S. Patton (1885-1945)
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COSC 1P02

• Audience
• planning to major in COSC
• Staff
• instructors Dave Hughes (J312) Dave Bockus
  (J324)
• mentor Baoling Bork (J304)
• tutorial leader
• lab demonstrators
• Lectures (AS216), labs (J301), tutorials (AS203)
• Web
• COSC http//www.cosc.brocku.ca/
• COSC 1P02 http//www.cosc.brocku.ca/offerings/cos
  c1p02/
• Email
• Dave Hughes hughesd_at_brocku.ca
• Dave Bockus bockusd_at_brocku.ca
• Succeeding in COSC 1P02
• labs/assignments

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Course Content and Procedures

• All course documents available through Computer
  Science Website
• www.cosc.brocku.ca/Offerings/1P02/
• COSC home page www.cosc.brocku.ca
• Outline
• Instructional labs
• lab participation
• Assignment preparation
• Help Desk (J304)
• submission (outside J332)
• return (J333)
• plagiarism
• Exams/tests
• lab vs written
• course procedures
• plagiarism
• students with computers
• Software JCreator or Dr. Java
• Libraries
• BasicIO

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Class Room

• Ground Rules
• Lecture conduct
• Cell Phones
• Laptops
• Contact information
• Email messages only accepted from a Brock server.
• Dave Bockus
• Open Door Policy (J324, Day Section)
• E-mail bockusd_at_brocku.ca
• MSN bockusd_at_hotmail.com

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Computer ScienceWhat is it?

• study of computer hardware and algorithms and
  data structures and how they fit into information
  systems.
• computer
• programmable machine.
• processes data into information.
• Algorithm
• well-defined sequence of steps to produce an
  outcome
• programming language
• Java

Hardware
Data In
Info Out
Algorithm Software
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Hardware Components

• processor (CPU)
• control unit (CU)
• controls system
• follows instructions
• arithmetic logic unit (ALU)
• performs operations (e.g. , -, , lt)
• main memory (RAM)
• volatile
• input devices
• transformation
• keyboard, scanner, sensor

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Hardware Components.

• output devices
• transformation
• monitor, printer, actuator
• auxiliary storage
• hard disk, floppy disk, CD-ROM, DVD, Data Keys
• communications
• Networks ( wired, broadband)
• modem, cable modem

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Data Representation
Data, what is stored.
Address, where the info is located.

• switchesbi-stable devices
• binary system
• positional (like decimal)
• bit
• byte
• megabyte (MB)
• memory organization
• storage cell
• address
• store(write)/fetch(read)

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Data Representation (2)

• All information is represented in binary code
• numbers
• characters
• coding scheme
• sound, images
• Digitization
• Important bytes of data only differ in how they
  are interpreted.
• The same byte can be viewed as
• Simple representation
• Numbers (integers and floats)
• Characters (abc)
• Part of Complex Objects
• Pictures, sounds, video
• Program
• Machine Code which instructs the hardware.
• Its all in the interpretation

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Instruction Processing

• machine language
• Opcode (operation code)
• Operand (source data to be used in the operation)
• CPU
• registers
• Special Registers IAR, IR
• bus
• machine (fetch/decode/execute) cycle
• fetch
• decode
• execute
• system clock
• 1 megahertz (Mhz) 1,000,000 cycles/second

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Fetch/Decode Cycle
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Coding Schemes
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Machine LanguageAssembly Language

• First generation
• One-to-one correspondence with hardware function
• Binary representation
• Operator (opcode)
• Operands
• Developed into Assembly by allowing mnemonics to
  represent the actual machine instructions.
• made life easier for the programmers.

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High-level Language

• Closer to problem domain
• One-to-many translation
• Code much easier to write and understand
• Made writing large programs much easier.
• Required
• Compiler
• Takes source program
• Converts to object program something the machine
  can understand
• Libraries
• linker
• Compile time vs Link time vs Execution time

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Software

• Software
• computer program
• instructions for machine execution
• Compiler
• Translation of a high level language into machine
  language.
• Program preparation
• edit
• editor
• compile
• compiler
• syntax errors
• link
• add in resources (code) from library
• execute
• execution (logic) errors (bugs)
• Development environment (IDE, e.g. DrJava,
  JCreator)

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Computer Programming
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Java

• Gosling (1990-92)
• Originally for consumer electronics
• embedded systems
• Platform independence
• Object-oriented
• programming as modeling
• Java as a better C
• Execution of Java programs
• platform independence
• machine language?
• Java bytecode
• Java interpreter

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Java Programming Concepts

• library (package)
• e.g. Media
• collection of useful classes
• imported to be used
• class
• e.g. Turtle
• definition of a kind of entity (object)
• defines operations (methods) entities can perform
• object
• one entity from a class (a turtle)
• created using new

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• variable
• e.g. yertle
• name that refers to an object or value
• method
• e.g. forward
• an operation that can be performed by an object
• statement
• a line of Java code
• method call statement
• request for an object to perform a method
• object.methodName(parameters)
• e.g. yertle.forward(40)

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Turtle Graphics

• Simple graphics facility
• Derived from Logo
• TurtleDisplayer
• a class in the BasicIO library
• canvas of 300 by 300 drawing units
• Turtle
• a class in the Media library
• draws on a canvas
• Drawing a square
• create displayer
• create turtle
• put turtle on canvas
• put pen down
• draw line
• turn corner
• repeat

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Assembly and Machine Language
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Executing an Assembly Language Program
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Executing a High-Level Language Program
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Turtle Displayer

• This is equivalent to a piece of paper which the
  turtle will draw on.
• Create the Displayer
• Put the turtle on the Displayer
• This also implies we can have more then 1 turtle
  on the same displayer.
• Displayer and Turtle are resources provided by
  libraries.
• We do not make the paper we use. We let someone
  else do this for us.
• Code is linked in to our program
• If you want a piece of paper you have to have a
  access to it.
• Same for a pencil
• Import statement allows us access to these
  libraries.

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A Java Program

• Draw a square
• Framework
• a program is a class
• code for a class is stored in a file
• a class is part of a package
• establish (import) environment (libraries)
• define names (variables) being used
• constructor is a method that is executed when an
  object is created
• contains actions (statements) to be performed
• main method creates an instance of the DrawSquare
  class to begin execution

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Basic Program Components

• package Example_2_1
• import BasicIO.
• import Media.
• import static java.lang.Math.
• public class DrawSquare
• private TurtleDisplayer display // display
  to draw on
• private Turtle yertle // turtle
  to do drawing
• public DrawSquare ( )
• display new TurtleDisplayer()
• yertle new Turtle()
• display.placeTurtle(yertle)
• yertle.penDown()
• yertle.forward(40)

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Draw Square Program Flow
package Example_2_1 import BasicIO. import
Media. import static java.lang.Math. /
This class is a program to draw a square using
Turtle Graphics. _at_author D. Hughes
_at_version 1.0 (July 2007) new concepts
java program structure, declarations,
constructor, object creation, object
assignment, method calls, turtle displayer,
turtle graphics / public class
DrawSquare private TurtleDisplayer
display // display to draw on private
Turtle yertle // turtle to do
drawing public DrawSquare ( )
/ The constructor. /
display new TurtleDisplayer() yertle
new Turtle() display.placeTurtle(yertle)
yertle.penDown()
yertle.forward(40) yertle.right(PI/2)
yertle.forward(40)
yertle.right(PI/2) yertle.forward(40)
yertle.right(PI/2)
yertle.forward(40) yertle.right(PI/2)
yertle.penUp()
display.close() // constructor
public static void main ( String args
) new DrawSquare()
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TurtleDisplayer Methods
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Turtle Methods
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The end