Flowcharts

Lecture 12

Symbol

Terminal Symbol: indicates the starting or stopping pointin the logic.

Input/Output Symbol:Represents an input or output process in an algorithm

Process Symbol:Represents any single process in an algorithm

Decision Symbol:Represents a decision in the logic involving the comparisonOf two values.

Predefined Process Symbol:

The three basic control structures

1. Sequence

Statemement a

Statemement b

Statemement c

2. Selection

Condition p?

Statemement a Statemement b

T F

Selection (2)

Condition p?

Statemement a

T

F

3. Repetition

Condition p?

Statemement block

T

F

Example 12.1 Add three numbers

A program is required to read three numbers, add them together and print their total.

• Defining diagram

Input Processing Output

Number1Number2Number3

Read three numbersAdd number togetherPrint total number

total

Solution Algorithm

Add numbers to total

ReadNumber1Number2number3

Print total

Start

Stop

Example 12.2 Find average temperature

• A program is required to prompt the terminal operator for the maximum and minimum temperature readings on a particular day, accept those readings as integers, and calculate and display to the screen the average temperature, calculated by (maximum temperature + minimum temperature)/2.

• Defining diagram

Input Processing Output

Max_tempMin_temp

Prompt for temperaturesGet temperaturesCalculate average temperatureDisplay average temperature

Avg_temp

Solution Algorithm

Example 12.3 Compute mowing time

• A program is required to read from the screen the lenght and widht of a rectangular house block, and the lenght and width of the rectangular house that has been built on the block. The algorithm should then compute and display the mowing time required to cut the grass around the house, at the rate of two square metres per minute.

• Defining diagram

Input Processing Output

Block_lenghtBlock_widthHouse_lenghtHouse_width

Prompt for block measurementsGet block measurementsPrompt for house measurementsGet house measurementsCalculate mowing areaCalculate mowing time

Mowing_time

Solution Algorithm

Flowchart and the selection control structure

Simple IF statement

Account_balance <

$300?

Service_charge = $5 Service_charge = $2

T F

Null ELSE statement

Student_attendance =

P/T?

Increment part_time_count

T

F

Combined IF statement

Student = P/T ANDGender =

F ?

Increment Female_part_time_count

T

F

Nested IF statement

IncrementCounter_A

Record

Code =`A‘ ?

IncrementCounter_B

IncrementCounter_C

IncrementError_counter

Record

Code =`A‘ ?

Record

Code =`A‘ ?

T

T

T

F

F

F

Example 12.4 Read three characters

• Design an algorithm that will prompt a terminal operator for three characters, accept those characters as input, sort them into ascending sequence and output them to the screen.

• Defining diagram

Input Processing Output

Char_1Char_2Char_3

Prompt for charactersAccept three charactersSort three charactersOutput three characters

Char_1Char_2Char_3

Solution Algorithm ?

Case Structure

CaseOf

variable

Statement_a Statement_b Statement_c Statement_d

Value 1 Value 2 Value 3 Value 4

Flowchart and Array

• Design a program that will prompt for and receive 18 examination scores from a mathematics test, compute the class average, and display all the scores and the class average to the screen.

• Defining diagram

Input Processing Output

18 exam scores Prompt the scoresGet scoresCompute class averageDisplay scoresDisplay class average

18 exam scoresClass_average

Control Structures required

1. An array to store the exam scores – called ´scores´

2. An index to identify each element in the array

3. A DO loop to accept the scores

4. Another DO loop to display the scores to the screen.

Solution Algorithm

Start

Total_score = zero

I = 1

Add scores(I) to

Total score

I = I + 1

Calculate average

I = I + 1

Prompt and get

Scores (I)

I = 1

I <= 18 ?

DisplayScores (I)

I <= 18 ?

Displayaverage

Stop

T

F

T

F

Flowchart and Module

Design a solution algorithm that will prompt a terminal operator for three characters, accept those characters as input, sort them into ascending sequence and output them to the screen. The algorithm is to continue to read characters until ´XXX`is entered.

• Defining diagram

Input Processing Output

Char_1Char_2Char_3

Prompt for charactersAccept three charactersSort three charactersOutput three characters

Char_1Char_2Char_3

Hierarchy chart

Process_three_characters

Sort_three_characters

Process_three_charactersStart

PromptFor

characters

Sort_Three_

characters

Outpurcharacters

Get characters

PromptFor

characters

Getcharacters

Stop

CharactersNOT = xxx ?F

T

Sort_three_characters

Start

Char_2 >Char_3 ?

Char_1 >Char_2 ?

Char_1 >Char_2 ?

SwapChar_2,Char_3

SwapChar_1,Char_2

SwapChar_1,Char_2

Stop

T

F

T

T

F

F

Assignment: Calculate Employee‘s pay

A program is required by a company to read an employee‘s number, pay rate and the number of hours worked in a week. The program is then to validate the pay rate and the hours worked fields and, if valid, compute the employee‘s weekly pay and print it along with the input data.

Assignment (cont‘)

Validation: According to the company‘s rules, the maximum hours an emplooye can work per week is 60 hours, and the maximum hourly rate is $25.00 per hour. If the hours worked field or the hourly rate field is out of range, the input data and an appropriate message is to be printed and the emplooye‘s weekly pay is not to be calculated.

Weekly pay calculation: Weekly pay is calculated as hours worked times pay rate. If more than 35 hours are worked, payment for the overtime hours worked is calculated at time-and half.

• Defining diagram

Input Processing OutputEmp_noPay_rateHrs_worked

Read employee detailsValidate input fieldsCalculate employee payPrint employee details

Emp_noPay_rateHrs_workedEmp_weekly_payError_message

Hierarchy chart

Compute_employee_pay

Calculate_Employee_pay

Validate_input_fields

Read_employee_details

Employee_details

Print_employee_details

Valid_input_fields

Solution Algorithm

Compute_employee_pay

Start

Read_Employee_

details

MoreRecods?

Validate_Input:fields

Stop

FieldsValid?

Calculate_Employee_

pay

Print_Employee_

details

Read_Employee_

details

Validate_input_fields

Start

Valid_input_fields = T

Pay_rate > $ 25

PrintError

message

Valid_Input_

Fields = F

Hours_Worked

> 60

PrintError

message

Valid_Input_

Fields = T

Stop