1. Control Structure Senior Lecturer
Siti Nurbaya Ismail
Senior Lecturer
Faculty of Computer & Mathematical Sciences
Universiti Teknologi MARA Kedah (e): (b):

2. Control Structure Previously… Previously… Sequential Selection
Creating a set of instructions to complete a task.
Selection
A decision within a computer program when the program decides to move on based on the results of an event.
Previously…
Iteration / Looping
Loop Control Structure
Basic Algorithm Using Looping
Calculate the total or sum
Calculate the average
Find maximum value and minimum value
Count
Single Looping
Nested Looping
Pseudo code & Flowchart
Determine Output / Tracing Table

3. Control Structure Today… Manipulate a series Sentinel Loop
Infinite Loop
Nested Loop  Quick Revision
Draw Diagram Using Nested Loop

4. Iteration Control Structure
Manipulate a series

5. Problem Solving: Manipulate a series
Calculate the total of the following series: … until 30 times {consistent sequence} =
Problem Definition:
Input
Process
Output
Nothing as the value for each number is identified
The first number is 3
The different between a number and second number is 3
The relation between next number and current number is
next number = current number + 3 OR
number = number + 3
Total of 30 numbers

6. Problem Solving: Manipulate a series
Calculate the total of the following series: … until 30 times {consistent sequence}
Start
total = 0
number = 3
counter = 1
While ( counter <= 30 )
total = total + number
number = number + 3
counter = counter + 1
endWhile
Display total
End

7. Problem Solving: Manipulate a series
Calculate the total of the following series: … until 30 times {a pattern of sequence}
Problem Definition:
Input
Process
Output
Nothing as the value for each number is identified
The first number is 1
The second number is 6
The different between first number and second number is 5
Starting from the 2nd number onwards, the different between the number and second number is consistent, icrease by 3
next number = current number + 3 OR
number = number + 3
Total of 30 numbers

8. Problem Solving: Manipulate a series
Calculate the total of the following series: … until 30 times {a pattern of sequence}
Start
total = 1
number = 6
counter = 2
While ( counter <= 30 )
total = total + number
number = number + 3
counter = counter + 1
endWhile
Display total
End

9. Problem Solving: Manipulate a series
You are given the following series. Calculate H where H = F + G F = … until 10 times G = … until 15 times H = F + G {a missing formula}
Problem Definition:
Input
Process
Output
Nothing as the value for each number is identified
Calculate Total F : number = number + 6 : 10 times
Calculate Total G : number = number + 4 : 15 times
Calculate Total H : Total F + Total G
Total of F + G

10. Problem Solving: Manipulate a series
Start
F = 0
number = 1
counter = 1
While ( counter <= 10 )
F = F + number
number = number + 6
counter = counter + 1
endWhile
G = 0
counter = 1
While ( counter <= 15 )
G = G + number
number = number + 4
H = F + G
Display H
End

12. Problem Solving: Manipulate a series
Calculate the factorial of a positive number. Factorial for n! as follows: Factorial = 1 x2 x 3 x … x n – 1 x n {given a formula}
Problem Definition:
Input
Process
Output n
n will be input by user, n is the end value
factorial = factorial * number
factorial

13. Problem Solving: Manipulate a series
Start
factorial = 1
Read n
number = 1
While ( number <= n )
factorial = factorial * number
number = number + 1
endWhile
Display factorial
End

14. Problem Solving: Manipulate a series
Flow Chart ?

15. Problem Solving: Manipulate a series

16. Iteration Control Structure
Sentinel Loop

17. Iteration: Sentinel Loop
scenario where the exact number of repetition is unknown but there must be a condition to stop the repetition
the syntax is:
all statements in between while .. endWhile will be executed when the condition is TRUE
the repetition is stop when the condition is FALSE.
Start
initial value of a loop
while ( condition )
statement(s) to be repeated
statement to update the condition
endWhile
End

18. Iteration: Sentinel Loop
Ask the user to enter a group of numbers. The last number is Display all entered numbers.
Input mark of students. Display mark which is less than 50. Stop the process when the user enters invalid mark.
Start
Read number
while ( number is =! 999 )
Display number
endWhile
End
Start
Read mark
while ( mark => 0.0 AND mark <= 100 )
If ( mark < 50 )
Display mark
EndIF
endWhile
End

19. Tracing Algorithm: Sentinel Loop
Given the following algorithm;
Start
sentinel = -1
count = 0
totalSquare = 0
Read x
while (x =! sentinel)
totalSquare = totalSquare + x2
count = count + 1
Read x
endWhile
Display “ total = “, totalSquare
Display nextline
Display “ count = “ , count
End
QUESTION
What is the value of the sentinel value used?
sentinel = -1
What is the body of repeat statements?
total-square = total-square + x2
count = count + 1
Read x
What is the value of total-square when the user enters the following data ?
total = 115
count = 3

20. Tracing Algorithm: Sentinel Loop
Given the following algorithm;
Start
i = 1
XX = 0
Display “enter an integer : “
Read number
Display “ MYSTERY MESSAGE ” , newline
while ( i <= number )
If ( number % i == 0)
XX = XX + 1 ;
Display i , “ ”
EndIF
i = i + 1
endWhile
diplay newline
Display “ There are ” , XX , “ MYSTERY MESSAGE FOR ”, number
End
QUESTION
Trace the pseudo code for the following data: 9 8 ?
Give a meaningful name for XX.
Replace MYSTERY MESSAGE FOR with a suitable words.

21. Problem Solving: Sentinel Loop
Find the best mark for the first test in a class. Assume that the number of student is unknown. The process stops when the user enters an invalid mark.
Problem Defination
In this problem, the user has to enter the student’s test mark many times. The process stops when the user enters invalid mark. Normally the valid mark is in the range of 0.0 to

22. Problem Solving: Sentinel Loop
Start
Display “ Enter test mark for the first student“
Read testMark
max = 0
while ( testMark => 0.0 AND testMark <= )
If (testMark > max )
max = testMark
EndIF
Display “ Enter test mark for next student “
endWhile
Display “The highest mark “, max
End

23. Problem Solving: Sentinel Loop
Ask the user to enter a set of numbers. Calculate how many number is divisible by 5. The process stops when the user enters 999. (pg 292)
Calculate the total of the following series and count how many numbers involved. (pg 296)
……………………
Count how many numbers which is divisible by 7 in between 1 and 100. (pg 297)
Calculate the mark and the grade for students. The mark is the average of two highest test mark between three test marks. The process stops when there are no more data to process. Use the following table to determine the grade. (pg 300)
Calculate the mark and the grade for students. The mark is the average of two highest test mark between three test marks. The process stops when there are no more data to process. Use the following table to determine the grade. (pg 300)
Display the following menu.
choice Operation
+ add 2 numbers
* multiply 3 numbers
- difference of 2 numbers
x exit
Ask the user to enter a choice. Repeat until the user enters ‘x’ as a choice. (pg 303)
Mark
Grade
100 – 80 A
79 – 65 B
64 – 60 C
59 – 40 D
39 – 0 E

24. Iteration Control Structure
Infinite Loop

25. Iteration: Infinite Loop
non stop loop
the repetition keeps running, it is never stop
the syntax is:
The above algorithm is missing the statement to increase the value of the variable number. It makes the condition (number ≤ 100) always true because the value of the variable number remains with 7. It makes the algorithm runs forever.
Start
count = 0
number = 7
while (number <= 100)
count = count + 1
endWhile
Display count
End

26. Iteration Control Structure
Nested Loop

27. Iteration: Nested Loop
inside a loop there is another loop ; inner loop and outer loop
The execution of this type of structure is, the computer will finish the inner loop for every iteration of outer loop
Start
count  0
number  7
while (number ≤ 100)
count  count + 1
endWhile
Display count
End

28. Iteration Control Structure
Draw a Diagram Using
Nested Loop

29. Iteration: Draw a Diagram Using Nested Loop
Display the following diagram:
&&&&&& 1 2 3 4
Start
row = 1
while (row < = 4)
row = row + 1
endWhile
End
EndIF
row = 4
col = 1
while (col <= 6)
Display “&”
col = col +1
EndWhile
Display newline
col = 6

30. Iteration: Draw a Diagram Using Nested Loop
Start
line = 1
While (line <= 5 )
If (line <= 3)
Else
Display newline
EndIF
line++
EndWhile
End
Iteration: Draw a Diagram Using Nested Loop
countSymbol = 1
While (countSymbol <= 5)
Display “$”
countSymbol++
EndWhile
Display newline
Display the following diagram:
$$$$$
##### 1 2 3 4 5
line = 5
line <= 3
countSymbol = 1
While (countSymbol <= 5)
Display “#”
countSymbol++
EndWhile
else
cauntSymbol = 5

32. Iteration: Draw a Diagram Using Nested Loop
Start
row = 1
while (row < = 7)
If ( (row = =1) OR (row = =7) )
Else
EndIF
Display newline
row ++
EndWhile
End
Iteration: Draw a Diagram Using Nested Loop
column = 1
while (column <= 6)
Display “$”
column++
endWhile
Display the following diagram:
$$$$$$
$ $
$ $ 1 2 3 4 5 6
column = 1
while (column <= 6)
If ( (column = =1) OR (column = = 6) )
Display “$”
Else
Display “ ”
EndIF
column++
endWhile
row = 6
column = 6

33. Iteration: Draw a Diagram Using Nested Loop
Flow Chart ?

34. Iteration: Draw a Diagram Using Nested Loop
Display the following diagram. @
Analysis: We can assume that the diagram is a square, consisting of five rows and five columns. The diagram consists symbols and white space. We can solve the problem using a matrix concept. 1 2 3 4 5
row = 5
column = 6

35. Iteration: Draw a Diagram Using Nested Loop
 In mathematics and computer science, a matrix is a set of numbers laid out in tabular form (in rows and columns). The matrix 5 x 5 means that the matrix consists of five rows and five columns. Each element of the matrix has the value of row and column as follows: @

36. Iteration: Draw a Diagram Using Nested Loop

37. Iteration: Draw a Diagram Using Nested Loop
When we compare the value of rows and columns to determine where the @ symbol is located and where is the location of the white space, we found that @ symbols are at the element where the value of row is greater or equal to column ( row ≥ column).

38. Iteration: Draw a Diagram Using Nested Loop
Start
row = 1
while (row < = 5)
row ++
endWhile
End
EndIF
Display the following diagram. @ 1 2 3 4 5
column = 1
while (column <= 5)
If (row => column)
Display
Else
Display “ “
EndIF
column++
EndWhile
row = 5
column = 6

39. Iteration: Draw a Diagram Using Nested Loop
Flow Chart ?

40. Iteration: Draw a Diagram Using Nested Loop
Symbols $ are at the following positions :
(1,1) (1,2) (1,3) (1,4) (1,5) (1,6)
(2,1) (2,6)
(3,1) (3,6)
(4,1) (4,6)
(5,1) (5,6)
(6,1) (6,6)
(7,1) (7,2) (7,3) (7,4) (7,5) (7,6)
Analysis:
- $ symbols are at the positions:
- all columns in the first row : ( when row == 1 )
- all columns in the seventh row : ( when row == 7 )
- all rows at the first column : ( when column == 1 )
- all rows at the sixth column : ( when column == 6 )
$ $ $ $ $ $
$ $
OUTPUT

41. Iteration: Draw a Diagram Using Nested Loop
Start
row = 1
while (row < = 7)
row ++
endWhile
End
EndIF
Display the following diagram.
$ $ $ $ $ $
$ $
column = 1
while (column <= 6)
If ((row==1)OR (row==7) OR (column==1) OR (column==6))
Display “$”
Else
Display “ “
EndIF
column++
EndWhile

42. Iteration: Draw a Diagram Using Nested Loop
Flow Chart ?

43. Iteration: Draw a Diagram Using Nested Loop
Write algorithm to display all of the following diagrams.