Unit 3

F1001 PROGRAMMING FUNDAMENTALS

UNIT

3

CONTROL STRUCTURE

 Sequential Control Structure
 Selection Control Structure
 Decision Control Structure

30


BLOCKS OF CODE
• Every programming language consists of thousand of statements.
• Thus, to simplify the execution of the programming language, all the statements in the programming
language is divided into blocks of code that have specific functions.
• Statement in a block of code is arranged sequentially in a program.
• A block of code is a group of statements that performs one particular task.

• The block is separated in several ways, like curly bracket “{“ and “}”, Begin and End statement and
others.
• Function is a block of code that has been assigned a name.
• Function is used as reference and execution for a block of code.
• Combination of blocks of code will produce a perfect program to be executed in a computer.
• Since the program comes from the different blocks of code, so, the flow needs to be controlled.
• Example of blocks of code:

void welcome ( )
{
printf (“****************************”); BLOCK OF
BLOCK BLOCK OF
BLOCK printf (“********WELCOME **********”); CODE
SEPARATO printf (“****************************”); CODE
SEPARATO
R }
R

PROGRAM FLOW
• Program flow in computer is controlled by the control structure.
• Control structure is a logical structure that controls the flow of instruction to be executed by computer.

• Control structure uses single entry and single exit; meaning it has only one beginning and one ending.

• There are three types of control structures:
1. Sequential control structure
2. Selection / decision control structure
a) If……endif
b) If……else
c) Nested if
3. Looping control structure
a) For
b) While
c) Do……while

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Sequential Control Structure
 In this control, every step will be executed one by one from top to bottom.
 Every box in control structure is a process. Every process is done sequentially.
 Format:
 Pseudocode: Flowchart

START
Start

Statement A
Statement A
Statement B
Statement B

End
END

 Example 1:
 Compute the total overtime wages of an employee.
 Problem analysis:
Input:
o Hours
o Basic_salary
o OT_rate
Process:
o Overtime equals OT_rate times Hours
o Salary equals Basic_salary plus Overtime
Output:
o Salary

 Algorithm:
1. Enter Hours, Basic_salary, OT_rate
2. Calculate overtime using formula:
Overtime = OT_rate * Hours
3. Calculate salary using formula:
Salary = Basic_salary + Overtime
4. Output Salary

32


 Pseudocode:
START
Input Hours, Basic_salary, OT_rate
Output Salary
END

 Flowchart:

START

Input Hours,
Basic_salary, OT_rate



Output
Salary

END

 Example 2:

 Problem: Mathematical operation: Get two numbers, then do adding, subtracting, multiplying
and dividing operations.
 Problem analysis:
Input:
o number_1, number_2
Process:
o Add 2 numbers:
Sum = number_1 + number_2
o Minus 2 numbers:

33


Subtract = number_1 – number_2
o Multiply 2 numbers:
Multiple = number_1 * number_2
o Division 2 numbers:
Divide = number_1 / number_2
Output:
o Sum, Subtract, Multiple and Divide

 Algorithm:
1. Enter 2 numbers
2. Add 2 numbers
3. Minus 2 numbers
4. Multiply 2 numbers
5. Division of 2 numbers
6. Display Sum, Subtract, Multiple and Divide

 Flowchart:

START

Input number_1,
number_2





Output Sum, Subtract, Multiple,
Divide

END 34


 Pseudocode:
START
Input number_1, number_2
Subtract = number_1 - number_2
Multiple = = number_1 * number_2
Output Sum, Subtract, Multiple, Divide
END

Selection / Decision Control Structure
 This type of control structure is usually used in structured programming
 This control structure will execute an instruction based on result of a condition or comparison.
 A condition will result either TRUE or FALSE.
 If the condition result is true, the control program will execute the instruction within the TRUE loop
operation.
 Otherwise, it will execute the next instruction or the instruction within the FALSE loop operation.
 Example 1:
 Condition: A person can obtain a license when he/ she is above 21 years old
Decision: If true then she / he is qualified to have driving license. If not he / she is not qualified to
have a driving license.
 Below is a flowchart of control structure:

35


START

True
Condition Input age

False Statement that will be
executed if condition True
If age > 21
Statement that will be is true
executed if condition
is not true False
Output
“Qualified”

Output “Not
Qualified”

END

 Type of selection / decision control structure:
1. If……endif
2. If……else
3. Nested if

1. IF…….ENDIF
 Rules:

If (condition)
Instruction (do this instruction if condition is true)
Endif

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If condition is not true, no instruction will be executed

 Pseudocode:
Flowchart:
If (condition)
START
True statement
Endif
True
Conditi Statement
on

False

END

 Example 1:
 Workers who work on shift 3 will receive additional Bonus RM50, where basic salary is
entered by workers.
 Problem analysis:
Input: 1. Shift
2. Basic_salary
Process: Bonus equals RM 50
If Shift equals to 3:
Salary equals Bonus plus Basic_salary
Output: Salary

 Algorithm:
1. Enter Basic_salary, Shift
2. Bonus equals to RM 50
3. Check workers Shift
3.1 If Shift equals to 3
Salary= Basic_salary + Bonus
4. Display Salary

37


 Flowchart:

START

Input Shift, Basic_salary

Bonus = 50

True
If Shift = Salary = Basic_salary + Bonus
3
False

Output Salary

END

 Pseudocode:

START
Input Shift, Basic_salary
Bonus = 50
If (Shift ==3)
Salary = Basic_salary + Bonus
End if
Output Salary
END

38


2. IF…….ELSE type
 A selection of control structure is used to select between two options
 Rules:  Pseudocode:

If (condition) If (condition)

True statement True statement

Else Else

False statement False statement

Endif Endif

 Flowchart:

START

False True
Conditi
on

Statement 2 Statement 1

END

 Example 1:
o Prepare a problem analysis, algorithm, flowchart and pseudocode to identify whether a
student is qualified to further her / his studies in any local university using his / her SPM
grade equal to 1.

o Problem analysis:
Input: Grade
Process: If Grade is equal to 1
Output “Qualified to further study”.

39


If not
Output “Not qualified to further study”.
Output: Display message qualified or not

o Algorithm:
1. Enter Grade
2. Check Grade
1.1 If Grade = 1
1.1.1 Output “Qualified to further study”
1.2 If not
1.2.1 Output “Not qualified to further study”

o Flowchart:

START

Input Grade

False True
If
Grade
== 1

Output “Not qualified Output “Qualified
to further study” to further study”

END

o Pseudocode:

START
Input Grade
If (Grade==1)
Output “Qualified to further study”

40


Else
Output “Not qualified to further study”

Endif
END

 Example 2:
o Problem:
Prepare the problem analysis, algorithm, flowchart and pseudocode to find
subtraction between two numbers that users enter.
o Problem analysis:
Input: num1, num2
Process: If num1 greater than num2
Result = num1 – num2
If not
Output: Result

o Algorithm:
1. Enter num1, num2
2. Compare the 2 numbers
2.1 If num1 greater than num2
2.1.1 Result = num1 – num2
2.2 If not
2.2.1 Result = num2 – num1
3. Display Result
START
o Flowchart:
Input num1, num2

False True
If num1 >
num2

Result = num2 – num1 Result = num1 – num2

Output Result
41

END


o Pseudocode:

START
Input num1, num2
If num1 > num2
Else

Endif

Output Result

END

3. NESTED IF

 There are 3 types:

1. Type 1:

If (condition1)
If (condition2)
If (condition3)
True statement
Endif
Endif
Endif

2. Type 2:
If (condition1)
If (condition2)
If (condition3)

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Statement that will be executed if condition1, condition2
and condition3 are true
Else
Statement that will be executed if condition1, and
condition2 are true but condition2 is false
Endif
Else
Statement that will be executed if condition1 is true but condition2
and condition3 is false
Endif
Else
Statement that will be executed if condition1 is false
Endif

3. Type 3

If (condition1)
Statement that will be executed if condition 1 is true
Else
If (condition 2)
Statement that will be executed if condition2 is true but
condition1 is false
Else
If (condition3)
Statement that will be executed if condition3 is true
but condition1 and condition2 are false
Else
Statement that will be executed if condition1,
condition2 and condition3 are false
Endif
Endif
End if

 Example Type 1:
o Problem:
To determine whether a candidate is qualified or not to get a scholarship based on his /
her study years, guardian’s salary and student CGPA. If the study year is more than 1,

43


student’s CGPA is not less than 3.00 and guardian’s salary is below than RM500,
student will be considered for a scholarship.

o Problem analysis:
Input: CGPA, Year, Salary.
Process:
1. Check if the student application’s can be considered or not for a scholarship.
1.1 If Year greater than 1
1.1.1 If CGPA greater than or equal to 3.00
1.1.1.1
If Salary is less than or equal to RM500
Output “Your application is under consideration”.
Output: Student status

o Algorithm:
1. Enter CGPA, Salary and Year
2. Check if the student application’s can be considered for a scholarship
2.11If year > 1
2.1.1 If CGPA >= 3.00
2.1.1.1 If salary <= RM500
Output “Your application is under consideration”
3.1 Display status

o Flowchart:

START

Input Year, CGPA, Salary

False True
If Year > 1

False If CGPA True
>= 3.00

Output “Your
False If Salary True
application is under
<= 500
consideration”

44

END


o Pseudocode:
START
If Year >1
If CGPA >= 3.00
If Salary <= RM500
Endif
Endif
Endif
END

 Example Type 2:
o Problem:
To determine whether a candidate is qualified or not to get a scholarship based on his /
her study years, guardian’s salary and student CGPA. If the study year is more than 1,
student’s CGPA is not less than 3.00 and guardian’s salary is below than RM500, student
will be considered for a scholarship. If the student is not qualified the message “Not
success” will be displayed.

o Problem analysis:
Input: CGPA, Year, Salary
Process:
1. Check if a student can be considered for a scholarship
1.1 If Year > 1
1.1.1 If CGPA >= 3.00
1.1.1.1 If Gaji <= 500
Output “You application is under consideration”
1.1.1.2 If not

45


Output “Not success”
1.1.2 If not
1.2 If not
Output: Student status

o Algorithm:
1. Enter CGPA, Year, Salary
2. Check if a student can be considered for a
scholarship
2.1 If Year > 1
2.1.1 If CGPA >= 3.00
2.1.1.1 If Salary <= RM500
Output “Your application is under consideration”.
2.1.1.2 If not
2.1.2 If not
2.2 If not
3. Display status
START

o Flowchart:

False True
If Year > 1

Output “Not False If CGPA True
success” >= 3.00

Output “Your
Output “Not False If Salary True
success” application is under
<= 500
consideration”

Output “Not
success”

46

END


o Pseudocode:
Input CGPA, Salary, Year
If (year > 1)
If (CGPA >= 3.00)
If (salary <= RM500)
Else
Output ”Not success”
Endif
Else
Endif
Else
Endif

 Example Type 3:
o Problem: Education status is determined based on the GPA achievement under the
following scheme:
GPA Status
3.50-4.00 Dean List
2.00-3.49 Pass
1.80-1.99 Conditional Pass
0.00-1.79 Fail

o Problem analysis:
Input: GPA
Process:
1. If (GPA < 0.00 AND GPA > 4.00)
Output “Invalid data”
2. If not

47


2.1 If (GPA >=3.5 AND GPA <= 4.00)
Output “Dean List”
2.2 If not
2.2.1 If (GPA >= 2.00 AND GPA < 3.50)
Output “Pass”
2.2.2 If not
2.2.2.1 If (GPA >= 1.80 AND GPA< 2.00)
Output “Conditional Pass”
2.2.2.2 If not
Output “Fail”
Output: Student education status

o Algorithm:
1. Enter student GPA
2. Compare student’s GPA to determine his/ her education status.
2.1 If (GPA < 0.00 AND GPA > 4.00)
Output “Invalid data”
2.2 If not
2.2.1 If (GPA >=3.50 AND GPA <= 4.00)
Output “Dean List”
2.2.2 If not
2.2.2.1 If (GPA >= 2.00 AND GPA < 3.50)
Output “Pass”
2.2.2.2 If not
2.2.2.2.1If (GPA >= 1.80 AND GPA < 2.00)
Output “Conditional Pass”
2.2.2.2.2If not
Output “Fail”
3. Print status

48


o Flowchart:

START

Input GPA

True False
If GPA < 0.00
&& GPA > 4.00

True False
If GPA >= 3.50 &&
Output “Invalid GPA <= 4.00
data”
Output “Dean True False
If GPA >= 2.00 &&
List” GPA < 3.50

True False
If GPA >= 1.80 &&
GPA < 2.00
Output “Pass”

Output
Output “Fail”
“Conditional Pass”

END

o Pseudocode:
START
Input GPA
If ((GPA < 0.00) AND (GPA > 4.00))

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Output "Invalid Data"
Else
If ((GPA >= 3.50) AND (GPA <= 4.00))
Output "Dean List"
Else
If ((GPA >=2.00) AND (GPA < 3.50))
Output "Pass"
Else
If ((GPA >= 1.80) AND (GPA < 2.00))
Output "Conditional Pass”
Else
Output "Fail"
Endif
Endif
Endif
Endif
END

 Usage of Logical Operator:
Symbol Symbol Example Result Description
(Pseudocode) (C Language)
AND && (1 > 3) && (10 < 20) FALSE Both sides of the condition must
be true
OR || (1 > 3) || (10 < 20) TRUE Either one of the condition must
be true
NOT ! ! (10 < 20) FALSE Change the operation either
from true to false or vise versa

o From the above table, the logical operator are AND, OR and NOT.
o Example using of AND operator:

If ((a < b) && (c > d))
printf(“Print a and c”);

o If condition (a < b) is true AND condition (c > d) is true then “Print a and c” will be
displayed. If one of the condition is not true then “Print a and c” will not be displayed.

50


o Example usage of OR operator:

If ((sales > 5000) || (hoursworked> 81))
bonus = 500;
else
bonus = 0;
o If the sales are more than 5000 OR working hours are more than 81, bonus RM500 will
be given. If either condition is not fulfilled, still the amount of RM500 will still be given
as bonus.
o If both conditions are false, then bonus will not be given.

Looping Control Structure
 A programming control structure that allows a series of instructions to be executed more than once.
The similar statement is repeated several times until the conditions are fulfilled.
 Three are three types of loop:
o For
o While
o Do…while
For While Do…while

For (initialize; condition; counter) While (condition) Do
True statement if condition is True statement True statement
fulfilled Endwhile While (condition)
Endfor

o Initialize value: a value to start a loop.
o Counter: to increase or decrease the initialize value.
o Rules for the condition:
- If the condition is true / fulfilled, the process will be performed.
 Format for Do …… while loop:
- Then, the program loops back and recheck the condition, if the condition is true /
fulfilled, repeat the process.
- When the condition is false, then exit the loop.
START
START
 Format for the For and While loops: Initialize

Initialize
Statement A

True Test
Test False
END condition
condition A
A False 51
True

Statement A END


 Example of loops usage:

o Problem: Prepare the problem analysis, algorithm, flowchart and pseudocode for the average of 5
numbers. Data will be entered by user.
o Problem analysis:
Input: 5 numbers
Process: The process of adding numbers will repeat until the condition to exit the loop is met.
Output: Average of 5 numbers
o Algorithm:
1. Initialize Counter=0; Average = 0; Total = 0
2. Input number
3. Add Total using formula:
Total = Total + number
4. Add Counter using formula:
Counter = Counter + 1
5. Compare whether Counter is greater than 5
If yes , go to step 6
If not, go to step 2
6. Calculate Average of numbers using formula;
Average = Total/5
7. Display Average

o Pseudocode:
For loop While loop Do…while loop
START START START
no = 0 no = 0 no = 0
Total = 0 Total = 0 Total = 0
Avg = 0 Avg = 0 Avg = 0
For (no=0; no<=5; no++) While (no <= 5) Do {
Input Num Input Num Input Num
Total = Total + Num Total = Total + Num Total = Total + Num
Endfor no = no + 1 no = no + 1
Avg = Total/5 Endwhile } While (no <= 5)

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Output Avg Avg = Total/5 Avg = Total/5
END Output Avg Output Avg
END END

o Flowchart for For and While loops:

START

no = 0

Total = 0

Avg = 0

For / False
While no Avg = Total/5
<= 5
True

Input Num Output Avg

Total = Total + Num END

no = no + 1

53


o Flowchart for Do……while loop:

START
Note:
no: a variable to control loop
no = 0 structure whether to continue or
exit from the loop
Total= 0
no + 1: a counter and it is very
Avg = 0 important. Without a counter, the
loop will be infinite

Input Num
Total = Total + Num: a variable to
compute the value
Total = Total + Num

no = no + 1

True False
no <= 5 Avg = Total/5

Output Avg

END
1. Initialize Counter = 0, Salary = 0;
2. Compare whether Counter is greater than 20 or not
o Example: To compute salary of 20 employees
If yes , out from the loop
Algorithm for For and While loops:
If not , go to step 3
3. Enter Basic_salary, Claim, O_time
4. Calculate EPF:
EPF = Basic_salary * 0.09
5. Calculate Salary using this formula:
Salary = Basic_salary + Claim + O_time – EPF
6. Display Salary
7. Add Counter using the formula:
54
8. Back to step 2


Flowchart for For and While loops:

START

no = 0

Salary = 0

False
For /
END
While no
True<= 20

Input
Basic_salary,
Claim, O_time



Output Salary

no = no + 1

Pseudocode for For loop:
START
no = 0
Salary = 0
For (no = 0, no <=20, no ++)
Input Basic_salary, Claim, O_time
Output Salary
Endfor 55
END


Pseudocode for While loop:

START
no = 0
Salary = 0
While no <=20
Gaji = Basic_salary + Claim + O_time – EPF
Output Salary
no = no + 1
Endwhile
END

Algorithm for Do……while loop:

1. Initialize Counter = 0, Salary = 0;
2. Input Basic_salary, Claim, O_time
3. Calculate EPF
4. Calculate Salary using this formula:
5. Add Counter using this formula:
6. Compare whether the Counter is greater than 20 or not
If yes , out of loop
If not, go to step 2
7. Display Salary

56


Flowchart for Do…..while loop:

START

no = 0

Salary = 0

Input
Basic_salary,
Claim, O_time



Output
Salary

no = no + 1

True False
no <= 5 END

START
no = 0
Pseudocode for Do…..while loop:
Salary = 0
Do
{
Output Salary
no = no + 1
} While (no <= 20) 57
END


o Dummy Data or Sentinel Value
- Value used to end the program. Dummy data must be different from the data to be
entered.
- Example:

START
Input name
While name != “XXX” Dummy data
Output name
Input mark
Output mark
Input name
Endwhile
END

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