1 introduction to flowcharting. 2 writing a program defining the problem –write down what the...

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Introduction to Flowcharting

2

Writing a program

• Defining the problem– Write down what the program will do

• Planning– Write down the steps, draw a flowchart

• Programming– Coding, including errors correction, testing

• Documenting– Adding comments

• Implementing– Improvement, making the program better

3

Objective

• A program can be divided into 3 parts:

– Input data– Processing data – Calculation, etc.– Output information/results

Input Processing Output

4

Arrows

• From Top to Bottom & from Left to Right

• Make turn

• Join together

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What is a Flowchart?

• A flowchart is a diagram that depicts the “flow” of a program.

• A diagram made up of symbols of various shapes connected by arrows.

• Those symbols indicate either actions to be taken or decisions to be made.

• It helps us planning & programming.

• The figure shown here is a flowchart for a pay-calculating program.

START

Display message “How many

hours did you work?”

Read Hours

Display message “How much do you get paid per

hour?”

Read PayRate

Multiply Hours by PayRate.

Store result in GrossPay.

Display GrossPay

END

6

Basic Flowchart Symbols

• Notice there are three types of symbols in this flowchart:– rounded rectangles

– parallelograms

– a rectangle

• Each symbol represents a different type of operation.

START

Display message “How many

hours did you work?”

Read Hours

Display message “How much do you get paid per

hour?”

Read PayRate

Multiply Hours by PayRate.

Store result in GrossPay.

Display GrossPay

END

Rounded Rectangle

Parallelogram

Rectangle

Rounded Rectangle

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Basic Flowchart Symbols

• Terminals– represented by rounded

rectangles

– indicate a starting or ending point

START

Display message “How many

hours did you work?”

Read Hours

Display message “How much do you get paid per

hour?”

Read PayRate

Multiply Hours by PayRate.

Store result in GrossPay.

Display GrossPay

END

Terminal

START

END Terminal

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Basic Flowchart Symbols

• Input/Output Operations– represented by

parallelograms

– indicate an input or output operation

START

Display message “How many

hours did you work?”

Read Hours

Display message “How much do you get paid per

hour?”

Read PayRate

Multiply Hours by PayRate.

Store result in GrossPay.

Display GrossPay

END

Display message “How many

hours did you work?”

Read Hours

Input/Output Operation

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Basic Flowchart Symbols

• Processes– represented by rectangles

– indicates a process such as a mathematical computation or variable assignment

START

Display message “How many

hours did you work?”

Read Hours

Display message “How much do you get paid per

hour?”

Read PayRate

Multiply Hours by PayRate.

Store result in GrossPay.

Display GrossPay

END

Multiply Hours by PayRate.

Store result in GrossPay.

Process

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Stepping Through the Flowchart

START

Display message “How many

hours did you work?”

Read Hours

Display message “How much do you get paid per

hour?”

Read PayRate

Multiply Hours by PayRate.

Store result in GrossPay.

Display GrossPay

END

Variable Contents:Hours: ?PayRate: ?GrossPay: ?

Stepping Through the Flowchart

In the next seven slides we will step through each symbol in the flowchart. We will show the program output and the contents of the variables.

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Stepping Through the Flowchart

How many hours did you work?

START

Display message “How many

hours did you work?”

Read Hours

Display message “How much do you get paid per

hour?”

Read PayRate

Multiply Hours by PayRate.

Store result in GrossPay.

Display GrossPay

END

Variable Contents:Hours: ?PayRate: ?GrossPay: ?

Step 1: An Output Operation

Stepping Through the Flowchart

Screen Output

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Stepping Through the Flowchart

How many hours did you work? 40

START

Display message “How many

hours did you work?”

Read Hours

Display message “How much do you get paid per

hour?”

Read PayRate

Multiply Hours by PayRate.

Store result in GrossPay.

Display GrossPay

END

Variable Contents:Hours: 40PayRate: ?GrossPay: ?

Step 2: An Input Operation

(User types 40)

Stepping Through the Flowchart

The value 40 is stored in Hours.

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Stepping Through the Flowchart

How much do you get paid per hour?

START

Display message “How many

hours did you work?”

Read Hours

Display message “How much do you get paid per

hour?”

Read PayRate

Multiply Hours by PayRate.

Store result in GrossPay.

Display GrossPay

END

Variable Contents:Hours: 40PayRate: ?GrossPay: ?

Step 3: An Output Operation

Stepping Through the Flowchart

Screen Output

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Stepping Through the Flowchart

How much do you get paid per hour? 20

START

Display message “How many

hours did you work?”

Read Hours

Display message “How much do you get paid per

hour?”

Read PayRate

Multiply Hours by PayRate.

Store result in GrossPay.

Display GrossPay

END

Variable Contents:Hours: 40PayRate: 20GrossPay: ?

Step 4: Input Operation

(User types 20)

Stepping Through the Flowchart

The value 20 is stored in PayRate.

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How much do you get paid per hour? 20

START

Display message “How many

hours did you work?”

Read Hours

Display message “How much do you get paid per

hour?”

Read PayRate

Multiply Hours by PayRate.

Store result in GrossPay.

Display GrossPay

END

Variable Contents:Hours: 40PayRate: 20GrossPay: 800

Step 5: The product of Hours times PayRate is stored in GrossPay

Stepping Through the Flowchart

The value 800 is stored in GrossPay.

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Stepping Through the Flowchart

Your gross pay is 800

START

Display message “How many

hours did you work?”

Read Hours

Display message “How much do you get paid per

hour?”

Read PayRate

Multiply Hours by PayRate.

Store result in GrossPay.

Display GrossPay

END

Variable Contents:Hours: 40PayRate: 20GrossPay: 800

Step 6: An Output Operation

Screen Output

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Four Flowchart Structures

• Sequence (TODAY)

• Decision

• Repetition

• Case

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Sequence Structure

• A series of actions are performed in sequence• The pay-calculating example was a sequence

flowchart.

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Connectors

• Sometimes a flowchart will not fit on one page.

• A connector (represented by a small circle) allows you to connect two flowchart segments.

A

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Connectors

A

A

START

END

•The “A” connector indicates that the second flowchart segment begins where the first segment ends.

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Review

• What do each of the following symbols represent?

(Answer on next slide)

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Answer

• What do each of the following symbols represent?

Terminal

Input/Output Operation

Process

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Review

• Name the four flowchart structures.

(Answer on next slide)

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Answer

• Sequence• Decision• Repetition• Case

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Flowcharting ProblemsWrite out the steps to solve the problem, then draw the diagram1.Flowchart a program to input the radius of a circle, and then calculate and print the area. The formula is Area = Pi * Radius2

2.Flowchart a program that will input four marks and calculate the average.

3.Flowchart a program that will take a temperature in Fahrenheit (F) convert it to Centigrade (C) The formulas are below.

• C = ( F - 32) / 1.8 – Output the results with a message that states:“ ___ degrees C is equal to ___ degrees F”