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Programming
8.2 Approach in Problem Solving

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• 8.2.1 Input Process Output (IPO)
Analysis
Approach in Problem Solving

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Learning Outcome
• Identify input, process and output from a
given problem

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Input Process Output (IPO)
Analysis
• The IPO is used to analyze problems and
develop algorithms
• Used to organize and summarize the
results of a problem analysis
• It shows where in the solution the
processing takes place

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Input Process Output (IPO)
Analysis
Input Processing Output
Processing items:
Algorithm
• It can also be represent using IPO
chart

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Input Process Output (IPO)
Analysis
To do the IPO Analysis, start with:
1- Output (Display the results)
2- Input (Read the data)
3- Process (Perform the computation)
Input :
Process :
Output :
Identify

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• Output should answer the following
question:
What does the user want to see
printed
on the printer, displayed on the
screen, or
stored in a file?
Input Process Output (IPO)
Analysis

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• Input should answer the following
question:
What information will the computer
need
to know to print, display, or store the
output items?
Input Process Output (IPO)
Analysis

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• Processing item:
An intermediate value that the
algorithm uses when processing the
input into the output
Input Process Output (IPO)
Analysis

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Analyze the Problem
• What is it you are trying to accomplish?
• What outcome are you trying to arrive at?
• List the Inputs and Outputs
• Often you work backwards from the Output
• List the Outputs, and then figure out what
Inputs you need in order to arrive at the
Outputs

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Example 1
Problem statement:
Calculate the area of a rectangle
We can summarize the information
contained in the problem statement as
follows
width
height
Analyze the Problem

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Problem Analysis:
To do the IPO Analysis, start with:
1 – Output
2 – Input
3 – Process
INPUT :
PROCESS :
OUTPUT :
Identify :
Analyze the Problem

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Problem Analysis:
Input: width, height
Process: area = width x height
Output: area of rectangle
Analyze the Problem

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Input Processing Output
width
height
Processing items:
area = width x height
Algorithm :
area of rectangle
Analyze the Problem
The Problem Analysis, can also be
represent using IPO (Input, Processing,
Output) Chart

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Example 2
Problem statement:
Find the average of three numbers
input by user
We can summarize the information
contained in the problem statement as
follows
Analyze the Problem

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Problem Analysis:
To do the IPO Analysis, start with:
1 – Output
2 – Input
3 – Process
INPUT :
PROCESS :
OUTPUT :
Identify :
Analyze the Problem

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Problem Analysis:
Input: number1, number2, number3
Process:
average = (number1 + number2 +
number3) / 3
Output: average
Analyze the Problem

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Input Processing Output
number1
number2
number3
Processing items:
average = (number1 +
number2 + number3) / 3
Algorithm :
average
Analyze the Problem
The Problem Analysis, can also be
represent using IPO (Input, Processing,
Output) Chart

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Example 3
Problem statement:
Determine the total cost of apples,
given the number of kilos of apples
purchased and the cost of apples per
kilo
We can summarize the information
contained in the problem statement as
follows
Analyze the Problem

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Problem Analysis:
To do the IPO Analysis, start with:
1 – Output
2 – Input
3 – Process
INPUT :
PROCESS :
OUTPUT :
Identify :
Analyze the Problem

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Problem Analysis:
Input:
Number of kilos of apples
Cost of apples per kilo
Process:
Total cost = Number of kilos of apples ×
Cost of apples per kilo
Output:
Total cost of apples
Analyze the Problem

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Analyze the Problem
The Problem Analysis, can also be
represent using IPO (Input, Processing,
Output) Chart
Input Processing Output
Number of kilos of
apples
Cost of apples per kilo
Processing items:
Total cost = Number of
kilos of apples × Cost of
apples per kilo
Algorithm :
Total cost of apples

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Summary
• Approaches in problem solving
• Identify Input Process Output (IPO) from a
problem statement
What have you learned ?

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• 8.2.2 Algorithm
• 8.2.3 Pseudocode
Approach in Problem Solving

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Learning Outcome
• Define algorithm
• Solve problem using pseudocode

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ALGORITHM
• The algorithm is the abstract idea of
solving a problem.
• An algorithm is a step-by-step
instructions that will transform the input
into the output
• It can be represent using pseudocode or
flow chart

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From Algorithms to Programs
Problem
C++ Program
1. Problem Analysis
2. Algorithm

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Algorithm in everyday’s life
• How to make a mug of hot coffee:
1.Start
• Boil water
• Prepare a mug
• Put a tea spoon of coffee & sugar
• Pour hot water
• Stir
• End

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ALGORITHM
can be described using three control structures
(Bohm and Jacopini-1966);
• A Sequence
o is a series of statements that execute one after
another
• A Selection – (branch)
o statement is used to determine which of two different
statements to execute depending on certain
conditions
• A Looping – (repetition)
o statement is used to repeat statements while certain

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PLANNING THE ALGORITHM
Identify:
INPUT :
PROCESS :
OUTPUT :
2. Transfer to pseudo code or flow chart
3. a. Must start with a start
b. Must close with an end
1. Do Problem Analysis

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TECHNIQUES TO REPRESENT
THE ALGORITHM
Pseudocode Flow chart
• Artificial, informal
language used to
develop algorithms
• Similar to everyday
English
• Graphical
representation of an
algorithm
• Special-purpose
symbols connected by
arrows (flow lines)
1.Pseudocod
e
2.Flow Chart

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TECHNIQUES TO REPRESENT
THE ALGORITHM
Calculate the area of a circle
Pseudocode Flow chart
Start:
Input radius
Calculate circle area
circle area = 3.142 * radius *
radius
Print the circle area
End:
1. Example of Pseudocode & Flow
chart
radius
circle area = 3.142 * radius *
radius
circle area
start
end

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1. Pseudocode
- Pseudocode Format
start
statement 1
statement 2
end
1
3
2
TECHNIQUES TO REPRESENT
THE ALGORITHM

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Algorithm Design : Pseudocode
Example 1
Problem statement:
Calculate the area of a rectangle
Remember!
1. Do Problem Analysis
2. Transfer to pseudo code or flow chart

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1. Problem Analysis:
Input: width, height
Process: area = width x height
Output: area of rectangle
Algorithm Design : Pseudocode

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Algorithm Design : Pseudocode
start
read width and height
calculate area
area of rectangle = width * height
print area of rectangle
end
2. Pseudocode

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IPO Chart with Pseudocode
Input Processing Output
width
height
Processing items:
area = width x height
Algorithm - Pseudocode:
Start
Read width and height
Calculate area
area of rectangle =
width * height
Print area
End
area of rectangle

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Algorithm Design : Pseudocode
Example 2
Problem statement:
Find the average of three numbers input
by user
Remember!
1. Do Problem Analysis
2. Transfer to pseudo code or flow chart

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1. Problem Analysis:
Input: number1, number2, number3
Process:
average = (number1 + number2 +
number3) / 3
Output: average
Algorithm Design : Pseudocode

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Algorithm Design : Pseudocode
start
input number1, number2, number3
calculate average
average = (number1 + number2 + number3) / 3
print average
end
2. Pseudocode

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IPO Chart with Pseudocode
Input Processing Output
number1
number2
number3
Processing items:
average = (number1 +
number2 + number3) / 3
Algorithm - Pseudocode:
Start
Input number1, number2,
number3
Calculate average
average = (number1 +
number2 + number3) / 3
Print average
End
average

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Algorithm Design : Pseudocode
Example 3
Problem statement:
Determine the total cost of apples,
given the number of kilos of apples
purchased and the cost of apples per
kilo
Remember!
1. Do Problem Analysis
2. Transfer to pseudo code or flow chart

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1. Problem Analysis:
Input:
Number of kilos of apples
Cost of apples per kilo
Process:
Total cost = Number of kilos of apples ×
Cost of apples per kilo
Output:
Total cost of apples
Algorithm Design : Pseudocode

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Algorithm Design : Pseudocode
start
Read Number of kilos of apples and Cost of
apples per kilo
Calculate Total cost
Total cost = Number of kilos of apples x Cost of
apples per kilo
Print Total cost of apples
end
2. Pseudocode

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Input Processing Output
Number of kilos of
apples
Cost of apples per kilo
Total cost = Number of kilos of
apples × Cost of apples per kilo
Algorithm - Pseudocode:
Start
Read Number of kilos of apples and
Cost of apples per kilo
Calculate Total Cost
Total cost = Number of kilos of
apples × Cost of apples
per kilo
Print Total cost of apples
End
Total cost of
apples
IPO Chart with Pseudocode

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Summary
• Approaches in problem solving
• Planning the algorithm
• Steps in building pseudocode
• Problem solving using pseudocode
What have you learned ?

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• 8.2.4 Flow Chart
Approach in Problem Solving

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Learning Outcome
• Solve problem using flow chart

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2. Flow Chart
- Flow Chart Format
TECHNIQUES TO REPRESENT
THE ALGORITHM
Statement 1
Statement 2
The statement
refers to any
input, output
& process
involved
start
end

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FLOW CHART - SYMBOLS
Graphic
Symbol
Name Meaning
Terminal
Symbol (oval)
indicates the beginning and end
points of an algorithm
Process
Symbol
(rectangle)
shows an instruction other than
input, output or selection
Input-Output
Symbol
(parallelogram)
shows an input or output operation

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FLOW CHART - SYMBOLS
Graphic
Symbol
Name Meaning
Disk Storage
Input-Output
Symbol (cylinder)
indicates input from or output to
disk storage
Printer Output
Symbol
shows hardcopy printer output
Selection Symbol
(diamond)
shows a selection process for two-
way selection

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FLOW CHART - SYMBOLS
Graphic
Symbol
Name Meaning
Flow Lines
(arrow)
indicates the logical sequence of
execution steps in the algorithm
Off-Page
Connector
provides continuation of a logical
path on another page
On-Page
Connector
(circle)
provides continuation of a logical
path at another point in the same
page

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Algorithm Design : Flow Chart
Example 1
Problem statement:
Calculate the area of a rectangle
Remember!
1. Do Problem Analysis
2. Transfer to pseudo code or flow chart

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1. Problem Analysis:
Input: width, height
Process: area = width x height
Output: area of rectangle
Algorithm Design : Flow Chart

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Algorithm Design : Flow Chart
2. Flow Chart
area = width * height
width, height
area
start
end

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IPO Chart with Flow Chart
Input Processing Output
width
height
Processing items:
area = width x height
Algorithm – Flow Chart:
area of rectangle
area = width * height
width, height
area
start
end

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Algorithm Design : Flow Chart
Example 2
Problem statement:
Find the average of three numbers input
by user
Remember!
1. Do Problem Analysis
2. Transfer to pseudo code or flow chart

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1. Problem Analysis:
Input: number1, number2, number3
Process:
average = (number1 + number2 + number3)
/ 3
Output: average
Algorithm Design : Flow Chart

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Algorithm Design : Flow Chart
2. Flow Chart
average = (number1 + number2 + number3) / 3
number1, number2, number3
average
start
end

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IPO Chart with Flow Chart
Input Processing Output
number1
number2
number3
Processing items:
average = (num1 + num2 + num3) / 3
Algorithm – Flow Chart:
average
average = (number1 + number2 + number3) / 3
number1, number2, number3
average
start
end

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Algorithm Design : Flow Chart
Example 3
Problem statement:
Determine the total cost of apples,
given the number of kilos of apples
purchased and the cost of apples per
kilo
Remember!
1. Do Problem Analysis
2. Transfer to pseudo code or flow chart

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1. Problem Analysis:
Input:
Number of kilos of apples
Cost of apples per kilo
Process:
Total cost = Number of kilos of apples ×
Cost of apples per kilo
Output:
Total cost of apples
Algorithm Design : Flow Chart

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Algorithm Design : Flow Chart
2. Flow Chart
Number of kilos of
apples,
Cost of apples per kilo
Total cost =
Number of kilos of apples x
Cost of apples per kilo
Total cost of apples
end
start

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IPO Chart with Flow Chart
Input Processing Output
Number of kilos of
apples
Cost of apples per kilo
Total cost = Number of
kilos of apples × Cost of
apples per kilo
Algorithm – Flow Chart:
Total cost of apples
Number of kilos of
apples, Cost of apples
per kilo
Total cost =
Number of kilos of apples
x Cost of apples per kilo
Total cost of apples
end
start

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Summary
• Approaches in problem solving
• Steps in building flow chart
• Problem solving using flow chart
What have you learned ?

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Revision
• What is IPO analysis?
• What is algorithm?
• What are the steps in planning your
algorithm?
• Differentiate between pseudocode and
flowchart.
What have you learned ?

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8.2 Approach in Problem Solving
8.2.5 Control Structure
8.2.5.2 Sequence

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8.2.5.1 Sequence
Learning Outcome
At the end of the lesson, students should be able
to :
1. Understand basic problem solving techniques.
• Use the sequence structured in problem solving.
• Develop flowchart through the process of top-down.

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8.2.5.1 Sequence
• The simplest programs consist just sequence of
statements :
• no loops, no selections amongst alternative actions, no
use of subroutines.

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8.2.5.1 Sequence
• Instruction in sequence programming are
executed sequentially one by one
• The sequence structure directs the computer to
process the instructions, one after another, in the
order listed in the program.
first instruction last instruction.

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8.2.5.1 Sequence

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8.2.5.1 Sequence
• Planning the Algorithm
• Record the algorithm using IPO analysis / IPO
chart.
Problem Analysis:
Input: sales
Process: bonus = sales * (0.05)
Output: bonus

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Algorithm Design : Pseudocode
start
input sales
bonus = sales * (0.05)
print bonus
end
Pseudocode
-tool programmers use to help them plan an
algorithm
-consist of short, English-like statements

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Algorithm Design : Flow Chart
Flow Chart
- Use
standardized
symbols to show
the steps the
computer need
to take to
accomplish the
program’s goal
start
bonus = sales *
(0.05)
end
sales
bonus

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8.2.5.1 Sequence

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8.2.5.1 Sequence
Problem Analysis:
Input: width, length, price of tile
Process:
area = width * length
total of price = area * price of tile
Output: total of price
• Planning the Algorithm
• Record the algorithm using IPO analysis / IPO
chart.

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Algorithm Design : Pseudocode
start
input width, length, price of tile
area = width * length
total price of tile = area * price of tile
print total price of tile
end
Pseudocode
-tool programmers use to help them plan an
algorithm
-consist of short, English-like statements

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Algorithm Design : Flow Chart
start
area = width * length
total price of tile = area * price of
tile
end
width
length
price of tile
Total price of
tile
Flow Chart
- Use
standardized
symbols to
show the steps
the computer
need to take to
accomplish the
program’s goal

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8.2.5.1 Sequence

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8.2.5.1 Sequence
Problem Analysis:
Input: hour
Process:
Total overtime payment = hour * 5.00
Output: total overtime payment
• Planning the Algorithm
• Record the algorithm using IPO analysis / IPO
chart.

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Algorithm Design : Pseudocode
start
input hour
total overtime payment = hour * 5.00
print total overtime payment
end
Pseudocode
-tool programmers use to help them plan an
algorithm
-consist of short, English-like statements

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Algorithm Design : Flow Chart
start
Total overtime payment =
hour * 5.00
end
hour
Total overtime
payment
Flow Chart
- Use
standardized
symbols to
show the steps
the computer
need to take to
accomplish the
program’s goal

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Summary
• Instruction in sequence programming are executed
sequentially one by one
• First step in the problem-solving process it to
analyze the problem
• Planning the algorithm is using IPO analysis / IPO
chart
• Programmer uses the pseudocode as a guide
when coding the algorithm
• Flow chart uses standardized symbols to show the
steps the computer needs to take to accomplish
the program’s goal

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8.0
PROGRAMMING
8.2: Approach in Problem Solving
8.2.5: Control Structure
8.2.5.2  Selection

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• At the end of this topic, students should
be able to:
a) explain the purpose of selection control
structure.
b) apply selection control structure in
problem solving.
Learning Outcome

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Control Structure : Selection
SELECTION Analogy
You need to choose to make “Coffee O” or
“Milk Coffee”

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Control Structure : Selection
SEQUENC
E
Control Structures
SELECTION LOOPING

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What is Selection Structure?
• The selection structure allows instructions
to be executed non-sequentially.
• It allows the comparison of two
expressions, and based on the
comparison, to select certain course of
action.
Control Structure : Selection

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Control Structure : Selection
if-else
Types of selection structure
nested if-else switch

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• If-else structure’s form
if (expression)
statement_1
else
statement_2
Selection  (1) if-else

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• In this form, the expression is first
evaluated.
• If it evaluates to non-zero (TRUE),
statement_1 is executed.
• Otherwise, statement_2 is executed.
• Either statement_1 or statement_2 is
executed but not BOTH.
Selection  (1) if-else

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• Pseudocode format:
Selection  (1) if-else
start
if (expression)
statement_1
else
statement_2
end

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• Flow chart format:
Selection  (1) if-else

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• Example 1:
Print “Excellent!” when user enter marks
greater than and equal to 80, else print
“Sorry, try again”.
Selection  (1) if-else
Remember to plan your algorithm!
1.Do IPO Analysis
• Transfer to Pseudocode or Flow
Chart

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• Example 1:
Print “Excellent!” when user enter marks
greater than and equal to 80, else print
“Sorry, try again”.
Selection  (1) if-else

96. 02/10/12
IPO Analysis:
Input: marks
Process:
if (marks >= 80)
print “Excellent”
else
print “Sorry, try again”
Output: “Excellent!” or “Sorry, try again”
Selection  (1) if-else

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• Pseudocode
Selection  (1) if-else
start
read marks
if (marks >= 80)
print “Excellent!”
else
print “Sorry, try again”
end

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• Flow chart
start
end
marks
“Excellent!”
marks >= 80
true “Sorry, try again”
false
Selection  (1) if-else

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• Example 2:
A high school poetry competition is open
only for students above 15 years old.
Display “Eligible” if the students meet the
requirement, else display “Not eligible” if
otherwise.
Selection  (1) if-else

100. 02/10/12
• Example 2:
A high school poetry competition is open
only for students above 15 years old.
Display “Eligible” if the students meet the
requirement, else display “Not eligible” if
otherwise.
Selection  (1) if-else

101. 02/10/12
IPO Analysis:
Input: age
Process:
if (age > 15)
print “Eligible”
else
print “Not eligible”
Output: “Eligible” or “Not eligible”
Selection  (1) if-else

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• Pseudocode
Selection  (1) if-else
start
read age
if (age > 15)
print “Eligible”
else
print “Not eligible”
end

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• Flow chart
start
end
age
“Eligible”
age > 15
true “Not eligible”
false
Selection  (1) if-else

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• Example 3:
If x is greater than y, display “x is bigger
than y” else display “x is smaller than y”.
Selection  (1) if-else

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• Example 3:
If x is greater than y, display “x is bigger
than y” else display “x is smaller than y”.
Selection  (1) if-else

106. 02/10/12
IPO Analysis:
Input: x,y
Process:
if (x > y)
print “x is bigger than y”
else
print “x is smaller than y”
Output: “x is bigger than y” OR “x is smaller than y”
Selection  (1) if-else

107. 02/10/12
• Pseudocode
Selection  (1) if-else
start
read x,y
if (x > y)
print “x is bigger than y”
else
print “x is smaller than y”
end

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• Flow chart
start
end
x,y
“x is bigger than y”
x > y
true “x is smaller than y”
false
Selection  (1) if-else

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Selection  (2) nested if-else
if-else
Types of selection structure
nested if-
else
switch

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• The if-else structure can also be nested to
any depth.
Selection  (2) nested if-else

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• The nested if-else if structured takes the general form:
if (expression_1)
statement_1;
else if (expression_2)
statement_2;
else if (expression_3)
statement_3;
else
statement_4;
Selection  (2) nested if-else

112. 02/10/12
• In this nested form, expression_1 is
evaluated. If it evaluates to non-zero
(TRUE), statement_1 is executed.
• If not, control goes to the second if, where
expression_2 is evaluated. If it evaluates
to non-zero (TRUE), statement_2 is
executed.
• If not, control goes to the third if, where
expression_3 is evaluated. If it evaluates
to non-zero (TRUE), statement_3 is
executed.
Selection  (2) nested if-else

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• If not, statement_4 is executed.
• Rules  Only ONE of the statements is
executed.
Selection  (2) nested if-else

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• Example 1:
if student’s grade is greater than or equal to 80
Print “A”
else if student’s grade is greater than or equal to
60
Print “B”
else if student’s grade is greater than or equal to
50
Print “C”
else
Print “Failed”
Selection  (2) nested if-else

115. 02/10/12
IPO Analysis:
Input: grade
Process: if (grade >= 80)
print “A”
else if (grade >= 60)
print “B”
else if (grade >= 50)
print “C”
else
print “Failed”
Output: “A” or “B” or “C” or “Failed”
Selection  (2) nested if-else

116. 02/10/12
• Pseudocode
Selection  (2) nested if-else
start
read grade
if (grade >= 80)
print “A”
else if (grade >= 60)
print “B”
else if (grade >= 50)
print “C”
else
print “Failed”
end

117. 02/10/12
• Flow chart
Selection  (2) nested if-else
start
end
grade
grade >= 80
true
“A”
false
grade >= 60
grade >= 50
“B”
“C”
false
false
“Failed”
true
true

118. 02/10/12
Selection  (2) nested if-else
• Example 2:
if (x > 0)
display "x is positive"
else if (x < 0)
display "x is negative"
else
display "x is 0"

119. 02/10/12
Selection  (2) nested if-else
IPO Analysis:
Input: x
Process: if (x > 0)
display "x is positive"
else if (x < 0)
display "x is negative"
else
display "x is 0“
Output: “x is positive“ or "x is negative“ or “x is 0”

120. 02/10/12
Selection  (2) nested if-else
• Pseudo code
start
read x
if (x > 0)
display "x is positive"
else if (x < 0)
display "x is negative"
else
display "x is 0"
end

121. 02/10/12
Selection  (2) nested if-else
• Flow chart
start
end
x
(x > 0)
true "x is
positive”
false
(x < 0) “x is
negative”
false
“x is 0”
true

122. 02/10/12
Selection  (3) Switch
if-else
Types of selection structure
nested if-else switch

123. 02/10/12
• Switch case statements are to check
several possible constant values for an
expression.
• Switch form:
switch (expression) {
case constant1: group of statements1
break
case constant2: group of statements2
break
. . .
default: default group of statements
}
Selection  (3) Switch

124. 02/10/12
• switch evaluates expression and checks if
it is equivalent to constant1, if it is, it
executes group of statements1 until it
finds the break statement.
Selection  (3) Switch

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• If expression was not equal
to constant1 it will be checked
against constant2. If it is equal to this, it
will execute statements2.
Selection  (3) Switch

126. 02/10/12
• If the value of expression DID NOT
match any of the previously specified
constants (you can include as
many case labels as values you want to
check), the program will execute the
statements included after the default.
Selection  (3) Switch

127. 02/10/12
iv) Selection - switch
switch Flow chart

128. 02/10/12
• Example 1:
Selection  (3) Switch
x Print
1 X is 1
2 X is 2
Other value Value of x unknown

129. 02/10/12
Selection  (3) Switch
IPO Analysis:
Input: x
Process:
switch (x)
{ case 1: print "x is 1“
break
case 2: print "x is 2“
break
default: Print "value of x unknown”
}
Output: "x is 1" or "x is 2" or "value of x unknown”

130. 02/10/12
Selection  (3) Switch
• Pseudocode
start
read x
switch (x)
{ case 1: print "x is 1“
break
case 2: print "x is 2"
break
default: print "value of x unknown”
}
end

131. 02/10/12
b) Flow chart
iv) Selection - switch

132. 02/10/12
SUMMARY
if-else
Types of selection structure
nested if-
else
switch
* Use an appropriate selection
control structure in problem solving

133. 02/10/12
Topic: 8.2
Approach in Problem Solving
8.2.5: Control Structure
8.2.5.3: Looping

134. 02/10/12
Learning Outcome
At the end of this topic, students should be able to:
• explain the purpose of looping control structure.
• apply looping control structure in problem
solving.

135. 02/10/12
What is looping control structure?
• The looping (or repetition) structure allows a
sequence of instructions to be executed
repeatedly until a certain condition is reached.
• The looping structure has three forms:
o while
o do..while
o for

136. 02/10/12
The essentials of looping (repetition)
• The loop counter (loop control variable ):
o Counts the number of repetitions in the counter-
controlled loop
o Controls the execution of loop
• The loop counter requires the following to be known in
advance:
1.Name of a loop counter
• Initial value of the loop counter
• Increment (or decrement) by which to modify the
loop counter in each traversal
• Condition to test the final value of loop counter

137. 02/10/12
1. The while Construct
The looping control structure:

138. 02/10/12
The while Construct
• The while construct has the general form:
while (expression) statement;
• where the expression is first evaluated.
• If it is true (not zero), the *statement(s) is
executed,
• else if it false (zero), the statement is bypassed.
* note: statement(s); which can be a block of statements –
more than 1 statement

139. 02/10/12
Applying Algorithm in while Construct
• Pseudocode
start
initialize counter
while (expression)
statement(s)
counter increment
end
12
4
3
* note: please refer to slide #4 for numbering details

140. 02/10/12
Applying Algorithm in while Construct
• Flow Chart start
initialize
counter
while
(expression)
statement(s)
True
counter increment
False
end

141. 02/10/12
The Counter Table for while Construct
counter expression input process output counter
increment
initial value of
counter condition to
test
IPO analysis
increment to
modify the loop
i i <= 3 input process output i = i + 1
xample of while counter table:

142. 02/10/12
Example 1: while Construct
• Problem Statement:
o Calculate the area of a rectangle for 3 times.
• Remember to plan your algorithm.
o Do Problem Analysis.
o Transfer to Pseudocode or Flow Chart.
width
height

143. 02/10/12
i i <= 3 width,height area = width * height area i = i + 1
while counter table
Example 1: while Construct
Problem Analysis:
Input: width, height
Process: area = width * height
Output: area

144. 02/10/12
i i <= 3 width,height area = width * height area i = i + 1
1 T 2
2 T 3
3 T 4
4 F Loop terminate
while counter table
Example 1: while Construct
Problem Analysis:
Input: width, height
Process: area = width * height
Output: area

145. 02/10/12
• Pseudocode
Example 1: while Construct
start
1. initialize counter
i = 1
2. while (i <= 3)
3. input width, height
4. calculate area of rectangle
area = width * height
5. print area
6. counter increment
i = i + 1
7. repeat until i > 3
end
IPO analysis
initial value of counter
condition to test
increment to
modify the loop
Repeat step 2 – 6 until
expression is false

146. 02/10/12
• Flow Chart
Example 1: while Construct
start
i = 1
(i <= 3)
width, height
True
i = i + 1
False
end
area = width *
height
area

147. 02/10/12
2. The do..while Construct
The looping control structure:

148. 02/10/12
The do..while Construct
• The do..while construct has the general form:
do
statement
while (expression);
• where the expression is last evaluated, after the
statement(s) is executed.
• This means the statement(s) in the do..while will
be executed at least once.

149. 02/10/12
Applying Algorithm in do..while
Construct
• Pseudocode
start
initialize counter
do
statement(s)
counter increment
while (expression)
end
12
4
3
* note: please refer to slide #4 for numbering details

150. 02/10/12
Applying Algorithm in do..while
Construct
• Flow Chart start
initialize
counter
while
(expression)
statement(s)
True
counter increment
False
end

151. 02/10/12
The Counter Table for do..while
Construct
counter input process output counter
increment
expression
initial value of
counter
condition to
test
IPO analysis
increment to
modify the loop
i input process output i = i + 1 i <= 3
ample of do..while counter table:

152. 02/10/12
Example 2: do..while Construct
• Problem Statement:
o Calculate the area of a rectangle for 3 times.
• Remember to plan your algorithm.
o Do Problem Analysis.
o Transfer to Pseudocode or Flow Chart.
width
height

153. 02/10/12
i width,height area = width * height area i = i + 1 i <= 3
do..while counter table
Example 2: do..while Construct
Problem Analysis:
Input: width, height
Process: area = width * height
Output: area

154. 02/10/12
i width,height area = width * height area i = i + 1 i <= 3
1 2 T
2 3 T
3 4 F
Loop terminate
do..while counter table
Example 2: do..while Construct
Problem Analysis:
Input: width, height
Process: area = width * height
Output: area

155. 02/10/12
• Pseudocode
Example 2: do..while Construct
start
1. initialize counter
i = 1
2. do
3. input width, height
4. calculate area of rectangle
area = width * height
5. print area
6. counter increment
i = i + 1
7. repeat while (i <= 3)
end
IPO analysis
initial value of counter
condition to test
increment to
modify the loop

156. 02/10/12
• Flow Chart
Example 2: do..while Construct
start
i = 1
(i <= 3)
width, height
True
i = i + 1
False
end
area = width *
height
area

157. 02/10/12
3. The for Construct
The looping control structure:

158. 02/10/12
The for Construct
• The for construct has the general form:
for (initialization; expression;
incrementation) statement;
• where the initialization refers to the initial value
of a loop counter.
• the expression determines whether the loop
should be continued; if it is true (not zero), the
*statement(s) is executed, else if it false (zero),
the for loop is terminated.
• The incrementation increments the loop counter.
* note: statement(s); which can be a block of statements –
more than 1 statement

159. 02/10/12
Applying Algorithm in for Construct
• Pseudocode
start
for (initialize counter; expression; counter
increment)
statement(s);
end
2
* note: please refer to slide #4 for numbering details
1 4 3

160. 02/10/12
The for loop is executed as follows:
start
for (initialize counter; expression; counter
increment)
statement(s);
end
o After one-time initialization, the expression is first
evaluated.
o If it is false, the for loop is terminated; if it is true the
statement(s) in the loop is executed.
o And then the incrementation is performed.
o The expression condition is again evaluated, until
the expression becomes false.

161. 02/10/12
Applying Algorithm in for Construct
• Flow Chart start
initialize
counter
(expression)
statement(s)
True
counter increment
False
end

162. 02/10/12
The Counter Table for for Construct
counter expression input process output counter
increment
initial value of
counter condition to
test
IPO analysis
increment to
modify the loop
i i <= 3 input process output i = i + 1
xample of for counter table:

163. 02/10/12
Example 3: for Construct
• Problem Statement:
o Calculate the area of a rectangle for 3 times.
• Remember to plan your algorithm.
o Do Problem Analysis.
o Transfer to Pseudocode or Flow Chart.
width
height

164. 02/10/12
i i <= 3 width,height area = width * height area i = i + 1
for counter table
Example 3: for Construct
Problem Analysis:
Input: width, height
Process: area = width * height
Output: area

165. 02/10/12
i i <= 3 width,height area = width * height area i = i + 1
1 T 2
2 T 3
3 T 4
4 F Loop terminate
for counter table
Example 3: for Construct
Problem Analysis:
Input: width, height
Process: area = width * height
Output: area

166. 02/10/12
• Pseudocode
Example 3: for Construct
start
1. initialize counter
i = 1
2. for (i <= 3)
3. read width, height
4. calculate area of rectangle
area = width * height
5. print area
6. counter increment
i = i + 1
7. repeat until i > 3
end
IPO analysis
initial value of counter
condition to test
increment to
modify the loop
Repeat step 3 – 7 until
expression is false

167. 02/10/12
• Flow Chart
Example 3: for Construct
start
i = 1
(i <= 3)
width, height
True
i = i + 1
False
end
area = width *
height
area

168. 02/10/12
Accumulating in Problem Solving
• Accumulating or summing is a task a program must
often perform.
• Accumulating means summing a group of numbers:
1.where a variable is added to another variable,
• which holds the value of the sum or total.
• The expression for accumulating is as follow:
sum = sum + num
total = total + marks
2 1
2 1

169. 02/10/12
How to apply Accumulating in Problem
Solving?
Example 4: Accumulating in Sequence
Structure
• Problem Statement:
o Calculate the average of three numbers.
Problem Analysis:
Input: num1, num2, num3
Process: total = num1 + num2 + num3
average = total / 3
or
average = (num1 + num2 + num3) / 3
Output: average
Accumulating

170. 02/10/12
How to apply Accumulating in
Looping?
Example 5: Accumulating in Looping
Structure
• Problem Statement:
o Calculate the average of three numbers.
Problem Analysis:
Input: num
Process: total = total + num
average = total / 3
Output: average
Accumulating

171. 02/10/12
Example 5: Accumulating in Looping
Structure
Problem Analysis:
Input: num
Process: total = total + num
average = total / 3
Output: average
total i i <=
3
num total = total +
num
i = i + 1 average = total /
3
average
0 1 T 70 70 2
2 T 80 150 3
3 T 90 240 4
4 F Loop terminate average = 240 / 3 80
Using accumulating in while construct (while counter table)

172. 02/10/12
Pseudocode for Accumulating in while
Construct:
start
1. initialize total
total = 0
2. initialize counter
i = 1
3. while (i <= 3)
4. input num
5. accumulate total
total = total + num
6. counter increment
i = i + 1
7. repeat until i > 3
8. calculate average
average = total / 3
9. print average
end
IPO analysis
initial value of counter
condition to test
increment to
modify the loop
Repeat step 3 – 6 until
expression is false
initial value of total
IPO analysis

173. 02/10/12
Flow Chart for Accumulating in while
Construct:
start
i = 1
(i <= 3)
num
True
False
end
total = total + num
i = i + 1
total = 0
average = total / 3
average

174. 02/10/12
Summary
• What have you learned?
o The three forms of looping control structure:
while
do..while
for
o The loop counter requirement.
o Apply looping control structure in problem
solving.
Remember to plan your algorithm.
Do Problem Analysis.
Transfer to Pseudocode or Flow Chart.
o Applying accumulating in looping.