Presentation on theme: "Chapter 2 - Problem Solving"— Presentation transcript:
1Chapter 2 - Problem Solving 2.1 Program Development Cycle2.2 Programming Tools
2Terminology tip A computer program may also be called: Project ApplicationSolution
32.1 Program Development Cycle Performing a Task on the ComputerProgram Planning
4Program Development Cycle Software refers to a collection of instructions for the computerThe computer only knows how to do what the program/programmer tells it to doTherefore, the programmer has to know how to solve problems
5Performing a Task on the Computer Determine OutputIdentify InputDetermine process necessary to turn given Input into desired OutputThese will be simple at first but can get very complicated.Think about programming MS Word
6Problem-solving: approach like algebra class How fast is a car traveling if it goes 50 miles in 2 hours?Output: a number giving the speed in miles per hourInput: the distance and time the car has traveledProcess: speed = distance / time
7Pictorial representation of the problem solving process
8Program Planning A recipe is a good example of a plan Ingredients and amounts are determined by what you want to bakeIngredients are inputThe way you combine them is the processingWhat is baked is the output
9Program Planning TipsAlways have a plan before trying to write a programThe more complicated the problem, the more complex the plan must bePlanning and testing before coding saves time coding
10Program development cycle 1. Analyze: Define the problem.2. Design: Plan the solution to the problem.3. Choose the interface: Select the objects (text boxes, buttons, etc.).
11Program development cycle continued 4. Code: Translate the algorithm into a programming language.5. Test and debug: Locate and remove any errors in the program.6. Complete the documentation: Organize all the materials that describe the program.
122.2 Programming Tools Flowcharts Pseudocode Hierarchy Chart Examples: Direction of Numbered NYC Streets AlgorithmClass Average Algorithm
13Programming ToolsThree tools are used to convert algorithms into computer programs:Flowchart - Graphically depicts the logical steps to carry out a task and shows how the steps relate to each other.Pseudocode - Uses English-like phrases with some Visual Basic terms to outline the program.Hierarchy chart - Shows how the different parts of a program relate to each other.
14AlgorithmA step by step series of instructions for solving a problem (a recipe is an example of an algorithm)
15Problem solving example How many stamps do you use when mailing a letter?One rule of thumb is to use one stamp for every five sheets of paper or fraction thereof.
16Algorithm1. Request the number of sheets of paper; call it Sheets. (input)2. Divide Sheets by 5. (processing)3. Round the quotient up to the next highest whole number; call it Stamps. (processing)4. Reply with the number Stamps. (output)
17FlowchartsGraphically depict the logical steps to carry out a task and show how the steps relate to each other.
21PseudocodeUses English-like phrases with some Visual Basic terms to outline the task.
22Pseudocode example Determine the proper number of stamps for a letter Read Sheets (input)Set the number of stamps to Sheets / 5 (processing)Round the number of stamps up to the nextwhole number (processing)Display the number of stamps (output)
23Hierarchy chartsShow how the different parts of a program relate to each otherHierarchy charts may also be calledstructure chartsHIPO (Hierarchy plus Input-Process-Output) chartstop-down chartsVTOC (Visual Table of Contents) chartsAll are similar to a company’s organization chart.
24Hierarchy charts example Each entry represents a module
25Divide-and-conquer method Used in problem solving – take a large problem and break it into smaller problems solving the small ones firstBreaks a problem down into modulesUsed with the other toolsMost common way in programming to solve problems
26Statement structuresSequence – follow instructions from one line to the next without skipping over any linesDecision - if the answer to a question is “Yes” then one group of instructions is executed. If the answer is “No,” then another is executedLooping – a series of instructions are executed over and over
29Direction of Numbered NYC Streets Algorithm Problem: Given a street number of a one-way street in New York City, decide the direction of the street, either eastbound or westboundDiscussion: in New York City even numbered streets are Eastbound, odd numbered streets are Westbound
33Class Average Algorithm Problem: Calculate and report the grade-point average for a classDiscussion: The average grade equals the sum of all grades divided by the number of studentsOutput: Average gradeInput: Student gradesProcessing: Find the sum of the grades; count the number of students; calculate averageWe need a loop to read and then add (accumulate) the grades for each student in the class. Inside the loop, we also need to total (count) the number of students in the class. See Figures 2.8 to 2.10.grade = sum of grades / number of students.
35Pseudocode Program: Determine the average grade of a class Initialize Counter and Sum to 0Do While there are more dataGet the next GradeAdd the Grade to the SumIncrement the CounterLoopComputer Average = Sum / CounterDisplay Average
37CommentsWhen tracing a flowchart, start at the start symbol and follow the flow lines to the end symbolTesting an algorithm at the flowchart stage is known as desk checkingFlowcharts, pseudocode, and hierarchy charts are program planning tools that are not dependent on the programming language being used
38Comments continuedThere are four primary logical programming constructssequencedecisionloopunconditional branchThere are four primary logical programming constructs: sequence, decision, loop,and unconditional branch. Unconditional branch, which appears in some lan-guagesas Goto statements, involves jumping from one place in a program to anoth-er.Structured programming uses the first three constructs but forbids the fourth.
39Unconditional branch Appear in some languages as Goto statements Involves jumping from one place in a program to anotherStructured programming uses the sequence, decision, and loop constructs but does not use the unconditional branch
40Tips and tricks of flowcharts Flowcharts are time-consuming to write and difficult to updateFor this reason, professional programmers are more likely to favor pseudocode and hierarchy chartsBecause flowcharts so clearly illustrate the logical flow of programming techniques, they are a valuable tool in the education of programmers
41Tips and tricks of pseudocode There are many styles of pseudocodeSome programmers use an outline formSome use a form that looks almost like a programming languageWill have to fill in the details when actually coding
42Tips and tricks of hierarchy charts Many people draw rectangles around each item in a hierarchy chartDo either way