Chapter 3Planning Your Solution

CMPF144 Introduction to Problem Solving and Basic CMPF144 Introduction to Problem Solving and Basic ComputerComputer

OverviewOverview Communicating with the Computer Organizing the Solution with Tools Testing the Solution Coding the Solution

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ObjectivesObjectives List and describe development tools Use problem analysis chart Use interactivity chart Use IPO chart Use algorithms (flowcharts and pseudocode) Describe importance of documentation

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Communicating with Communicating with ComputerComputer

We use programming language to communicate with a computer

Different type of programming language applies different syntax. SyntaxSyntax: the rules governing the computer operating

system, language and application Bug Bug : Coding error in a computer program DebuggingDebugging: Process to find and correct the coding errors

(bugs)

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Organizing Solution with Organizing Solution with ToolsTools

Four (4) categories of tools can be used to solve problems on a computer: Problem Analysis Chart (PAC) Interactivity Chart / Structure Chart IPO Chart Algorithm

Flowchart

pseudocode

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Problem Analysis Chart Problem Analysis Chart (PAC)(PAC) Shows a beginning analysis of the problem

Programmer will try to understand and analyze requirements of the problem

Allows programmer to glean only facts from the problem Separated into four (4) parts:

1. The given data

2. The required results

3. The processing that is required in the problem

4. A list of solution alternatives

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Basic Structure of Basic Structure of Problem Analysis ChartProblem Analysis Chart

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Problem Analysis Chart for Problem Analysis Chart for the Payroll Problemthe Payroll Problem

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Interactivity Chart / Interactivity Chart / Structure ChartStructure Chart Shows the overall layout or structure of the solution

Divide the processing identified into subtasks called modulesmodules these modules are connected together to show the interaction of

processing between modules Each module contain tasks for one function, not more than 20

instructions Example of function:

Enter data

Print result

calculate result

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Interactivity Chart (Cont.)Interactivity Chart (Cont.)

All modules are being controlled by a Control or Main Module

The breakdown (in the format of chart) allows programmer to view a complex problem in a few simpler parts.

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Example of Interactivity Example of Interactivity ChartChart

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Do you know what are these Do you know what are these symbols???symbols???Triangle on upper left of box??Circle in chart??Diamond shape after Module2??

Basic Interactivity Chart for Basic Interactivity Chart for the Payroll Problemthe Payroll Problem

The control module, read module, calculation module, and print module are BASIC to most programs.

From there, add other modules as needed along with the addition of processing symbols to show: Duplicates Decision Repetition in a loop

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Completed Interactivity Completed Interactivity Chart – The Payroll Chart – The Payroll

ProblemProblem

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Extends and organizes information in problem analysis chart (PAC)

Consists of four (4) main sections: Input Processing Module reference Output

14 IPO ChartIPO Chart

IPO Chart (Cont.)IPO Chart (Cont.)

Shows more detail/information about: What data items are input?? What processing takes place on each specific data?? What information is output??

Sequence of completing IPO Chart:1.Output

2.Input

3.Processing

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Is the sequence logical?? Why??

IPO Chart for IPO Chart for the Payroll Problemthe Payroll Problem

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Shows the sequence of instructions, which will form solution

A good algorithm’s criteria: Instructions cannot assume anything Cannot skip steps Must be executable one step at a time Must be 100% complete

Two types of algorithm representation: Flowchart Pseudocode

17 AlgorithmAlgorithm

18 FlowchartFlowchart

Graphical representation of algorithm, which shows the flow of the processing from the beginning to the end of a solution.

A flowchart always starts at the top of the page and flows to the bottom

There are flowchart symbols for use with various types of processing.

Flowchart SymbolsFlowchart Symbols19

Flowchart Symbols (Cont.)Flowchart Symbols (Cont.)20

Flowchart - the Payroll ProblemFlowchart - the Payroll Problem21

22Flowchart -Flowchart -

ReadRead Module in the Payroll Problem Module in the Payroll Problem

23Flowchart – Flowchart –

Calc Calc Module in the Payroll ProblemModule in the Payroll Problem

24Flowchart and Pseudocode for Flowchart and Pseudocode for

PrintPrint Module in the Payroll Problem Module in the Payroll Problem

Overall Overall Flowchart - Flowchart - The Payroll The Payroll ProblemProblem

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How to simplify this How to simplify this flowchart??flowchart??

Algorithm which is represented in simple English form

Each instruction is written on a separate line Starts with “Start/Begin” and terminates with

“End” Keywords and instructions are written from top

to bottom, with only ONE entry and ONE exit. Groups of statements are formed into module,

and each module is given a specific name (however, this is optional).

26 PseudocodePseudocode

Important keywords:

1. A computer can receive information Keyword: Read, Get

2. A computer can show information Keyword: Display, Print, Write

3. A computer can perform arithmetic calculation

27 Pseudocode (Cont.)Pseudocode (Cont.)

4. A computer can assign value to memory location Keyword: Set, Initialize

5. A computer can compare two variables to decide which action to be taken Keyword; IF….ELSE…..END_IF

6. A computer can repeat a group of action. Keyword: WHILE…END_WHILE, REPEAT…..UNTIL

28 Pseudocode (Cont.)Pseudocode (Cont.)

Overall Pseudocode – Overall Pseudocode – The Payroll ProblemThe Payroll Problem

Begin

REPEAT

Get Hours, PayRate

GrossPay = Hours * PayRate

Display GrossPay

UNTIL NoMoreEmployee = True

End

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Exercise (1)Exercise (1)

Try to organize solution for problem illustrated below, with the help of FOUR (4) tools that you have learnt in this chapter.

Build a program that read the value of the Build a program that read the value of the height, width and length of a box from height, width and length of a box from the user and print its volume.the user and print its volume.

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Exercise (2)Exercise (2)

Try to organize solution for problem in pp.76, PROBLEMS, Q6 with the help of FOUR (4) tools that you have learnt in this chapter.

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Consists of two main types: Internal documentation External documentation

32 DocumentationDocumentation

For programmers Made up of remarks written with the

instructions to explain what is being done in the computer program, so that it can b easily understood by other programmers

Example: what is the main purpose of developing this program

What are the meaning of certain code blocks

Status of program development

??

33 Internal DocumentationInternal Documentation

For end users Made up of manuals or help menus written

about the solutions. Example:

Tutorial which shows the steps to use program

Installation instruction

Help files

??

34 External DocumentationExternal Documentation

to make sure that the solution meets requirements of user

to check for errors in logic or in setup of the expressions and equations.

programmer selects test data test data (a set of values for input data)and works them through every step in the solution. Example: to test expression X/Y

Test data for X and Y should be any numbers other than 1. WHY??

35 Testing the SolutionTesting the Solution

To be performed after the completion of analyzing problem and organizing the solution.

A process of converting algorithm into real program by using appropriate type of programming language

Python : to be covered in practical class

36 Coding the SolutionCoding the Solution