COMP 14 Introduction to Programming

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COMP 14Introduction to Programming

• Jason Jerald
• June 23, 2006

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from Last Time

• Homework 1 due at midnight
• Review of Chapter 1
• Installation of jGRASP
• jGRASP getting started tutorial
• Did anyone make it to page 20
• Any problems?

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Objectives

• Learn about different types of computers.
• Explore the hardware and software components of a
  computer system.
• Learn what an algorithm is and explore
  problem-solving techniques.
• Become aware of structured and object-oriented
  programming design methodologies.

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Chapter 1 Objectives

• Learn about the language of a computer.
• Learn about the evolution of programming
  languages.
• Examine high-level programming languages.
• Discover what a compiler is and what it does.
• Examine a Java program.
• Examine how a Java program is processed.

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Reading Check-Up

• ________- computer components including the CPU,
  main memory, I/O devices, and secondary storage
• ________ - the brain of the computer that
  processes data
• ________ - computer instructions to solve a
  problem
• The digits 0 and 1 are called _________
• or the shortened term ________

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An Overview of the History of Computers

• 1950s Very large devices available to a select
  few.
• 1960s Large corporations owned computers.
• 1970s Computers got smaller and cheaper.
• 1990s Computers got cheaper and faster and were
  found in most homes.

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Elements of a Computer System

• A computer has two components
• Hardware
• Software

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Hardware Organization
CPU
memory
motherboard
hard drive
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Hardware vs. Software
A computer is made up of hardware and software
Software
Hardware

• CPU
• ex 2 GHz Pentium IV
• input/output
• keyboard
• monitor
• network card
• main memory
• ex 256 MB RAM
• secondary memory
• ex 20 GB hard drive

• operating systems
• Windows XP
• Mac OS X
• applications
• games
• Microsoft Word
• Internet Explorer

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Main Memory

• Ordered sequence of cells
• AKA Random Access Memory (RAM)
• Directly connected to the CPU
• All programs must be brought into main memory
  before execution
• When power is turned off, everything in main
  memory is lost

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The CPU and Main Memory
Memory
CPU
Central Processing Unit - A chip that
executes program instructions
Each memory cell has a numeric address, which
uniquely identifies it
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Secondary Storage

• Provides permanent storage for information
• Retains information even when power is off
• Examples of secondary storage
• Hard Disks
• Floppy Disks
• ZIP Disks
• CD-ROMs
• Tapes

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Input Devices

• Definition devices that feed data and computer
  programs into computers
• Examples
• Keyboard
• Mouse
• Secondary Storage

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Output Devices

• Definition devices that the computer uses to
  display results
• Examples
• Printer
• Monitor
• Secondary Storage

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Input/Output Devices
I/O devices facilitateuser interaction
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Opening MS Word

• Use the mouse to select MS Word
• The CPU requests the MS Word application
• MS Word is loaded from the hard drive to main
  memory
• The CPU reads instructions from main memory and
  executes them one at a time
• MS Word is displayed on your monitor

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Questions

• _________ - a unique location in memory
• _________ - stores information permanently
• Instructions executed by the CPU must be first
  loaded to ________

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Software Categories

• Operating System
• controls all machine activities
• provides the user interface to the computer
• first program to load when a computer is turned
  on
• manages computer resources, such as the CPU,
  memory, and hard drive
• examples Windows XP, Linux, Mac OS X
• Application
• generic term for any other kind of software
• examples word processors, missile control
  systems, games

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Operating System (OS)

• OS monitors overall activity of the computer and
  provides services
• Written using programming language
• Example services
• memory management
• input/output
• storage management

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Application Programs

• Perform a specific task
• Run by the OS
• Written using programming languages
• Example programs
• Word Processors
• Spreadsheets
• Games

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Questions

• Classify the following pieces of software as
  operating system (OS) or application (app)
• Microsoft Windows 2000
• Microsoft PowerPoint
• Linux
• Your COMP 14 programs

___
___
___
___
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Problem Solving

• The purpose of writing a program is to solve a
  problem
• The general steps in problem solving are
• understand the problem
• dissect the problem into manageable pieces
• design a solution
• consider alternatives to the solution and refine
  it
• implement the solution
• test the solution and fix any problems that exist

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Algorithm

• A sequence of instructions used to carry out a
  task or solve a problem
• May be written in either English or pseudocode
• outline of a program that could be translated
  into actual code
• May need refinement as you work
• Write out your algorithm before you begin
  programming

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Problem-Analysis-Coding-Execution
most important step
without computer
with computer
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Algorithm Design Example

• Problem Convert change in cents to number of
  half-dollars, quarters, dimes, nickels, and
  pennies to be returned.
• Example
• given 646 cents
• number of half-dollars divide 646 by 50
• quotient is 12 (number of half-dollars)
• remainder is 46 (change left over)
• number of quarters divide 46 by 25
• quotient is 1 (number of quarters)
• remainder is 21 (change left over)
• number of dimes, nickels, pennies
• result 12 half-dollars, 1 quarter, 2 dimes, 0
  nickels, 1 penny

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Resulting Algorithm

• Get the change in cents
• Find the number of half-dollars
• Calculate the remaining change
• Find the number of quarters
• Calculate the remaining change
• Find the number of dimes
• Calculate the remaining change
• Find the number of nickels
• Calculate the remaining change
• The remaining change is the number of pennies.

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Exercise

• Execution of c2ab in a computer

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Programming Methodologies

• Two basic approaches to programming design
• Structured design
• Object-oriented design

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Structured Design

• A problem is divided into smaller sub-problems.
• Each sub-problem is solved.
• The solutions of all sub-problems are combined to
  solve the problem.

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Object-Oriented Design (OOD)

• In OOD, a program is a collection of interacting
  objects
• An object consists of data and operations
• Steps in OOD
• Identify objects.
• Form the basis of the solution.
• Determine how these objects interact.

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Its All About Data

• Software is data
• numbers, characters
• instructions, programs
• Hardware stores and processes data
• read, write
• add, subtract, multiply, divide

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Analog vs. Digital

• Analog
• continuous wave forms
• ex sound, music on an audio tape
• Digital
• the information is broken down into pieces, and
  each piece is represented separately
• is ultimately represented as series of 0s and 1s
  for low voltage and high voltage
• can be copied exactly
• ex music on a compact disc

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Language of a Computer

• Machine language is the most basic language of a
  computer.
• A sequence of 0s and 1s.
• Every computer directly understands its own
  machine language.
• A bit is a binary digit, 0 or 1.
• A byte is a sequence of eight bits.

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Representing Text Digitally

• All information in a computer is digitized,
  broken down and represented as numbers.

H i , H e a t h e r .
72 105 44 32 72 101 97 116
104 101 114 46
Corresponding upper and lower case letters are
separate characters.
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Language of a Computer

• Machine language the most basic language of a
  computer
• A sequence of 0s and 1s
• binary digit, or bit
• sequence of 8 bits is called a byte
• Every computer directly understands its own
  machine language
• why can't Windows programs run on Apple computers?

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Bit Permutations
Each additional bit doubles the number of
possible permutations
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Bit Permutations

• Each permutation can represent a particular item
• There are 2N permutations of N bits
• N bits are needed to represent 2N unique items

21 2 items
22 4 items
23 8 items
24 16 items
25 32 items
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Binary Numbers

• N bits to represent 2N values
• N bits represent values 0 to 2N-1
• Example 5 bits
• 32 unique values (0-31)
• 000002 010
• 111112 3110

24 23 22 21 20
16 8 4 2 1 31
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Questions Binary Numbers

• Whats the maximum value a 6-bit number can
  represent?
• Whats the decimal representation of 111010?
• Whats the binary representation of 35?

26-163
25124123122021120058
35101000112
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Storage Capacity

• Every memory device has a storage capacity,
  indicating the number of bytes (8 bits) it can
  hold

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Assembly and Machine Language
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Machine Language

• Early computers programmed in machine language
  (only 0s and 1s)
• Assembly languages were developed to make
  programmers job easier
• Assembler translates assembly language
  instructions into machine language

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Programming Languages

• High-level languages make programming easier
• Closer to spoken languages
• Examples
• Basic
• FORTRAN
• COBOL
• C/C
• Java

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Java and Machine Language

• To run a Java program
• Java instructions need to be translated into an
  intermediate language called bytecode.
• The bytecode is interpreted into a particular
  machine language.

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Compiler

• Compiler A program that translates a program
  written in a high-level language into the
  equivalent machine language.
• (In the case of Java, this machine language is
  the bytecode.)
• Java Virtual Machine (JVM) A hypothetical
  computer developed to make Java programs machine
  independent.

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A Java Program

• public class ASimpleJavaProgram
• public static void main(String args)
• System.out.println("My first Java
  program.")
• System.out.println("The sum of 2 and 3
  " 5)
• System.out.println("7 8 " (7 8))
• Sample Run
• My first Java program.
• The sum of 2 and 3 5
• 7 8 15

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Processing a Java Program

• Program written in Java using the Editor and
  compiled to Bytecode using the Compiler.
• Loader transfers the compiled code (bytecode)
  into main memory and loads the necessary
  Libraries.
• Interpreter reads and translates each bytecode
  instruction into machine language and then
  executes it.

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Chapter Summary

• A computer system is made up of hardware and
  software components.
• An algorithm is a step-by-step, problem-solving
  process in which a solution is arrived at in a
  finite amount of time.
• The three steps of the problem-solving process
  are analyze the problem and design an algorithm,
  implement the algorithm in a programming
  language, and maintain the program.
• The two basic approaches to programming design
  are structured design and object-oriented design.

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Chapter Summary

• Computers understand machine language it is
  easiest for programmers to write in high-level
  languages.
• A compiler translates high-level language into
  machine language.
• The Java steps required to execute a program are
  edit, compile, load, and execute.

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To do

• Read ch. 2, pages 27-64 (material to be on an
  upcoming quiz Tuesday)
• Assignment 2 due Wednesday
• There are many small problems here, so get
  started early, (try to do about 20 of the work
  per day)

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Whats Ahead...

• Java Basics
• Assignments
• Assignment 1 due tonight
• Assignment 2 due Tuesday
• Quiz Tuesday computers and Java basics