Lecture 2 Problem Solving

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Lecture 2Problem Solving

• ENGR17 Engineering Programming
• Section 1
• Fall 2001

9/11/01
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Outline

• Six problem-solving steps used to create a
  computer program
• Complete an IPO chart
• Plan an algorithm using pseudocode and flowcharts
• Desk-check an algorithm
• Code and execute the algorithm

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Creating Computer Solutions
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Analyzing the Problem

• Determine the output(goal or purpose of solving
  the problem)
• Determine the input(information needed to reach
  the goal)
• Use an IPO (Input, Processing, Output) chart to
  organize and summarize the results of problem
  analysis

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Analyzing the Problem
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Analyzing the Problem

• Most difficult problem-solving step
• Problem specification can contain too much or too
  little information
• Distinguish between information that is missing
  in the problem specification, and information
  that is not explicitly stated

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Analyzing the Problem
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IPO Chart
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Analyzing the Problem
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Planning the Algorithm

• Algorithm the steps that will transform the
  input into the output
• Enter input items
• Process the data (usually by doing some
  calculations)
• Print or display the output items
• Tools
• IPO chart
• Pseudocode
• Flowcharts

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Planning the Algorithm
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Pseudocode Flowcharts

• Use standardized symbols, connected with
  flowlines, to show the steps the computer needs
  to take to accomplish the programs goal

Start/Stop
Process
Input/Output
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Hints for Writing Algorithms
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Hints for Writing Algorithms
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Hints for Writing Algorithms
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Hints for Writing Algorithms
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Hints for Writing Algorithms
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Desk-checking the Algorithm

• Refers to completing each step in the algorithm
  manually, using a set of sample data for input
  values
• Verifies that the algorithm is not missing steps
• Verifies that the existing steps are correct and
  in the proper order
• Also called hand-tracing
• Can use a desk-check table

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Desk-checking the Algorithm
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Desk-checking the Algorithm
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Desk-checking the Algorithm
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Problem Solving Summary

• Problem-solving steps used to create a computer
  program
• Analyze the problem
• Plan the algorithm
• Desk-check the algorithm
• Code the algorithm into a program
• Desk-check the program
• Evaluate and modify the program
• IPO charts
• Planning an algorithm using pseudocode and
  flowcharts
• Desk-checking an algorithm

continued
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Completing the Problem-Solving Process
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The C Programming Language

• Object-oriented successor to the
  procedure-oriented C language
• C language
• 1972, Dennis Ritchie, Bell Laboratories
• C
• 1985, Bjarne Stroustrup, Bell Laboratories
• Can be used as a procedural as well as an
  object-oriented language

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Requirements for Creating C Program

• Text editor
• Used to enter the C instructions (source code)
• C compiler
• Converts source code into machine code (object
  code)
• Case sensitive

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Different C Systems

• Integrated Development Environment (IDE)
• Contain editor and compiler in one integrated
  environment
• Examples Microsoft Visual C, Borland C
  Builder
• Command-line compilers
• Contain only the compiler
• Require use of general purpose editor (NotePad,
  WordPad) to enter program instructions

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Coding the Algorithm

• Coded algorithm a program
• Starting Microsoft Visual C 5.0

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Program Instructions
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C Programs

• Use a precise syntax
• Can include comments (//)
• Contain at least one directive
• Must contain a function named main

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Other Coding Terminology

• Header files (.h)
• Keywords
• Functions and void functions ( and )
• Variables
• Statements ()
• Streams (cout and cin)
• Insertion operators (()
• Stream manipulators

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Evaluating and Modifying the Program

• Testing
• Execute the program and enter sample data
• Valid data
• Invalid data
• Debugging
• Locate and remove errors in a program
• Syntax error
• Logic error

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Executing a C Program

• Before it can be executed, a C program must be
  compiled (source code translated into object code)

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After Completing Program

• Assemble external documentation and keep in a
  safe place
• IPO chart
• Flowchart of pseudocode
• Printout of the program

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Programming Summary

• Origins of the C programming language
• Source code and object code
• Opening a C source file
• Coding an algorithm
• Compiling, building, and executing a C program
• Evaluating and modifying a program