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 Predefined Process Symbol: Decision Symbol: Represents a decision in the logic involving the comparison Of two values.

The three basic control structures

1. Sequence Statemement a Statemement b Statemement c

2. Selection Condition p? T F Statemement a Statemement b

Selection (2) Condition p? F T Statemement a

3. Repetition Condition p? F T Statemement block

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 Number1 Number2 Number3 Read three numbers Add number together Print total number total

Solution Algorithm Start Read Number1 Number2 number3 Add numbers to total Print total 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_temp Min_temp Prompt for temperatures Get temperatures Calculate average temperature Display 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_lenght Block_width House_lenght House_width Prompt for block measurements Get block measurements Prompt for house measurements Get house measurements Calculate mowing area Calculate mowing time Mowing_time

Solution Algorithm

Flowchart and the selection control structure

Simple IF statement Account_ balance < $300? T F Service_charge = $5 Service_charge = $2

Null ELSE statement Student_ attendance = F P/T? T Increment part_time_count

Female_part_time_count Combined IF statement Student = P/T AND Gender = F ? F T Increment Female_part_time_count

Nested IF statement T F F T F T Increment Counter_A Increment Record Code =`A‘ ? F F T Record Code =`A‘ ? Increment Counter_A Record Code =`A‘ ? F Increment Counter_B T Increment Error_counter Increment Counter_C

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_1 Char_2 Char_3 Prompt for characters Accept three characters Sort three characters Output three characters

Solution Algorithm ?

Case Structure Case Of variable Statement_a Statement_b Statement_c Value 2 Value 3 Value 4 Value 1 Statement_a Statement_b Statement_c Statement_d

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 scores Get scores Compute class average Display scores Display class average Class_average

Control Structures required An array to store the exam scores – called ´scores´ An index to identify each element in the array A DO loop to accept the scores Another DO loop to display the scores to the screen.

Solution Algorithm T F T F Start Calculate average Display average Total_score = zero I = 1 I = 1 Stop Prompt and get Scores (I) Display Scores (I) Add scores(I) to Total score I = I + 1 T I = I + 1 I <= 18 ? F T I <= 18 ? 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_1 Char_2 Char_3 Prompt for characters Accept three characters Sort three characters Output three characters

Hierarchy chart Process_three_ characters Sort_three_ characters

Process_three_characters Start Sort_ Three_ characters Prompt For characters Outpur characters Get characters Prompt For characters Characters NOT = xxx ? F Stop Get characters T

Sort_three_characters Start T Char_1 > Char_2 ? F Swap Char_1, Char_2 Char_2 > Char_3 ? T F Swap Char_2, Char_3 Char_1 > Char_2 ? T F Swap Char_1, Char_2 Stop

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 Output Emp_no Pay_rate Hrs_worked Read employee details Validate input fields Calculate employee pay Print employee details Emp_weekly_pay Error_message

Compute_employee_pay Hierarchy chart Compute_employee_pay Employee_details Valid_input_ fields Read_employee_ details Validate_input_ fields Calculate_ Employee_pay Print_employee_ details

Solution Algorithm

Compute_employee_pay Fields Valid? Start Read_ Employee_ details Calculate_ Employee_ pay More Recods? Print_ Employee_ details Validate_ Input: fields Stop Read_ Employee_ details

Validate_input_fields Start Hours_ Worked > 60 Valid_input_ fields = T Print Error message Pay_rate > $ 25 Print Error message Valid_ Input_ Fields = T Valid_ Input_ Fields = F Stop