Problem solving and programming control structures.pptx

PROGRAMMING
APPROACH
IN PROBLEM
SOLVING

1. 1 APPROACH IN PROBLEM SOLVING
1.1.1 Input Process Output (IPO)
Analysis

LEARNING OUTCOME
• Identify input, process and output
from a given problem

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

ANALYSIS
Input Processing
Output
Processing items:
Algorithm
• It can also be represent using
IPO chart

ANALYSIS
Identify
Input :
Process
:
Output :
To do
the IPO
Analysi
s, start
with:

ANALYSIS
• 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?

ANALYSIS
• Input should answer the
following question:
What information will the computer
need
to know to print, display, or store the
output items?

ANALYSIS
• Processing item:
An intermediate value that the
algorithm uses when processing the
input into the output

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

follow
s
Example 1
Problem statement:
Calculate the area of a rectangle
We can summarize the information
contained in the problem statement
as
ANALYZE THE PROBLEM
heigh
t
width

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

ANALYZE THE PROBLEM
Problem Analysis:
 Input: width, height
 Process: area = width x height
 Output: area of rectangle

Input
width
heigh
t
ANALYZE THE PROBLEM
Processing
Processing items:
area = width x
height
Algorithm
:
Output
area of
rectangle
The Problem Analysis, can also be
represent using IPO (Input,
Processing, Output) Chart

ANALYZE THE PROBLEM
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
 Problem Analysis:
 Input: number1, number2, number3
 Process:
 average = (number1 + number2 + number3) / 3
 Output: average

Input
number
1
number
2
number
3
ANALYZE THE PROBLEM
Processing
Processing items:
average = (number1 +
number2 + number3) /
3
Algorithm
:
Output
averag
e

ANALYZE THE PROBLEM
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
 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
Input
Number of kilos
of apples
Cost of apples
per kilo
Processing
Processing items:
Total cost = Number of
kilos of apples × Cost
of apples per kilo
Algorithm
:
Output
Total cost of
apples

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

APPROACH IN PROBLEM SOLVING
• 1.1.2 Algorithm
• 1. 1.3 Pseudocode

LEARNING OUTCOME
• Define algorithm
• Solve problem using
pseudocode

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

FROM ALGORITHMS TO PROGRAMS
Problem
C++ Program
1. Problem Analysis
2. Algorithm

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

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)
statement is used to repeat statements while certain
conditions are met
ALGORITHM

PLANNING THE ALGORITHM
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
Identify:
INPUT :
PROCESS :
OUTPUT :

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

ALGORITHM
Pseudocode
Start:
Input radius
Calculate circle
area
circle area = 3.142 * radius
* radius
Print the circle area
End:
1. Example of Pseudocode & Flow chart
Calculate the area of a circle
radiu
s
circle area = 3.142 * radius
* radius
circle area
Flow chart
start
en
d

1. Pseudocode
- Pseudocode
Format
start
statement 1
statement
2
end
ALGORITHM
1
3
2

ALGORITHM DESIGN : PSEUDOCODE
Example 1
Problem statement:
Remember!

 1. Problem Analysis:

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

IPO CHART WITH PSEUDOCODE
Input
width
heigh
t
Processing
Processing items:
area = width x
height
Algorithm -
Pseudocode:
Start
Read width and
height Calculate area
area of rectangle
= width * height
Print
area End
Output
area of
rectangle

Example 2
Problem statement:
Find the average of three numbers input
by user
Remember!

 Input: number1, number2, number3
 Process:
 average = (number1 + number2 + number3) / 3
 Output: average

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

02/10/1
Input
number
1
number
2
number
3
Processing
Processing items:
3
Algorithm -
Pseudocode:
Start
Input number1,
number2, number3
Calculate average
3
Print
Output
averag
e

Example 3
Problem statement:
kilo
Remember!

 Input:
per kilo Process:
 Output:

02/10/1
2. 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

02/10/1
Input
Number of kilos
of apples
Cost of apples
per kilo
Processing
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
Output
Total cost
of apples

SUMMARY
• Approaches in problem solving
• Planning the algorithm
• Steps in building pseudocode
• Problem solving using
pseudocode

• Flow Chart

LEARNING OUTCOME
• Solve problem using flow
chart

ALGORITHM
Statement
1
Statement
2
2. Flow Chart
- Flow Chart Format
start
The statement
refers to any
input, output
& process
involved
en
d

02/10/1
FLOW CHART - SYMBOLS
Graphi
c
Symbo
l
Nam
e
Meanin
g
Terminal indicates the beginning and end
Symbol (oval) points of an algorithm
Process
Symbol
(rectangle
)
shows an instruction other
than input, output or
selection
Input-Output
Symbol
(parallelogra
shows an input or output
operation

02/10/1
Graphi
c
Symbo
l
Nam
e
Meanin
g
Disk Storage
Input-Output
Symbol
(cylinder)
indicates input from or
output to disk storage
Printer
Output
Symbol
shows hardcopy printer
output
(diamond
)
Selection Symbol shows a selection process for two-
way
selection

Graphi
c
Symbo
l
Nam
e
Meanin
g
Flow
Lines
(arrow)
indicates the logical sequence
of execution steps in the
algorithm
Off-Page
Connecto
r
provides continuation of a
logical path on another page
On-Page
Connecto
r (circle)
provides continuation of a
logical path at another point in
the same page

ALGORITHM DESIGN : FLOW CHART
Example 1
Problem statement:
Remember!

2. Flow Chart
start
width, height
area = width *
height
area

02/10/1
IPO CHART WITH FLOW CHART
Input
width
heigh
t
Processing
Processing items:
area = width x
height
Output
area of
rectangle
Algorithm – Flow
Chart:
start
width, height
area = width *
height
area

Example 2
Problem statement:
Find the average of three numbers input
by user
Remember!

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

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

02/10/1
Input
number
1
number
2
number
3
Processing
Processing items:
average = (num1 + num2 + num3) /
3
Output
averag
e
Algorithm – Flow Chart:
start
number1, number2, number3
average = (number1 + number2 +
number3) / 3
average

Example 3
Problem statement:
kilo
Remember!

 Input:
per kilo Process:
 Output:

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
2. Flow Chart
start
en
d

02/10/1
Input
Number of kilos
of apples
Cost of apples
per kilo
Processing
Total cost = Number of
kilos of apples × Cost
of apples per kilo
Algorithm – Flow
Chart:
Output
Total cost of
apples
en
start
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

SUMMARY
• Approaches in problem
solving
• Steps in building flow chart
• Problem solving using flow
chart

REVISION
• What is IPO analysis?
• What is algorithm?
• What are the steps in planning
your algorithm?
• Differentiate between
pseudocode and
flowchart.

1.2 CONTROL STRUCTURE
1.2.1SEQUENCE

SEQUENCE
Control Structures
SELECTION LOOPING

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.

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

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.

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

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

Flow Chart
- Use
standardized
symbols to
show the steps
the computer
need to take to
accomplish the
program’s goal
star
t
en
d
sales
bonus = sales * (0.05)
bonus

8.2.5.1 SEQUENCE
IPO chart.
Problem Analysis:
Input: width, length, price of tile
Process:
area = width * length
total of price = area * price of
tile
Output: total of price

Pseudocode
plan an algorithm
start
input width, length, price of tile
total price of tile = area * price of tile
print total price of tile
end

star
t
en
d
width
length
price of
tile
total price of tile = area * 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

8.2.5.1 SEQUENCE
IPO chart.
Problem Analysis:
Input: hour
Process:
Total
overtime
payment =
hour * 5.00
Output:

Pseudocode
plan an algorithm
start
input hour
total overtime payment = hour * 5.00
print total overtime payment
end

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

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

1.2.2 SELECTION

LEARNING OUTCOME
• 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.

CONTROL STRUCTURE : SELECTION
SELECTION Analogy
You need to choose to make “Coffee O”
or “Milk Coffee”

SEQUENC E
Control
Structures
SELECTION LOOPING

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.

if-else
Types of selection
structure
nested if-
else
switc
h
if-else-if

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

• 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.

• Pseudocode format:
start
if
(expression
)
statement_
1 else
statement_
2
end

• Flow chart
format:

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

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

IPO Analysis:
Input: marks
Process:
if (marks >= 80)
print “Excellent”
else
print “Sorry, try
again”
Output:
“Excellent!” or
“Sorry, try

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

en
d
• Flow chart
start
mark
s
marks >=
80
true
“Excellent!”
“Sorry, try
again”
false

• 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.

• 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.

IPO Analysis:
Input: age
Process:
if (age > 15)
print “Eligible”
else
print “Not
eligible”
Output:
“Eligible” or
“Not eligible”

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

en
d
• Flow chart
star
t
age
age >
15
true
“Eligible
”
“Not
eligible”
false

• Example 3:
If x is greater than y, display “x is
bigger than y” else display “x is
smaller than y”.

• Example 3:
If x is greater than y, display “x is
bigger than y” else display “x is smaller
than y”.

IPO Analysis:
Input: x,y
Process:
if (x > y)
print “x
is bigger
than y”
else
print “x
is
smaller
than y”

• Pseudocode
start
read
x,y if (x
> y)
print “x
is

en
d
• Flow chart
star
t
x,y
x > y
true
“x is bigger than
y”
“x is smaller than
y”
false

SELECTION  (2) NESTED IF-ELSE
if-
else
Types of selection
structure
nested if-
else
switc
h
if-else-if

SELECTION  (2) IF-ELSE…IF
• The if-else structure can also be nested
to any depth.

• 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;

• 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

• If not, statement_4 is executed.
• Rules  Only ONE of the statements
is executed.

• 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”

IPO Analysis:
Input: grade
Process: if (grade >= 80)
print “A”
else if (grade >= 60)
print “B”
print “C”
else
print “Failed”
Output: “A” or “B”
or “C” or “Failed”

• Pseudocode
start
read grade
if (grade >= 80)
print “A”
else if (grade
>= 60)
print “B”
print “C”
else
print “Failed”
end

en
d
• Flow chart
start
grade
true
“A”
“B”
“C”
grade >= 80
false
grade >= 60
false
grade >= 50
false
“Failed”
true
true

• Example 2:
if (x > 0)
display "x is
positive" else if (x <
0)
display "x is
negative" else
display "x is 0"

IPO Analysis:
Input: x
Process: if (x > 0)
display "x is
0)
display "x is
negative" else
display "x is 0“
Output: “x is positive“
or "x is negative“ or “x is

• Pseudo code
start
read x
if (x > 0)
display "x is
0)
display "x is
negative" else
display "x is 0"
end

• Flow chart
star
t
x true "x is
positive
”
“x is
negative
”
(x > 0)
false
(x < 0)
false
“x is
0”
end
true

SELECTION  (3) NESTED IF ELSE
if-
else
Types of selection
structure
nested if-
else
switch
if-else-if

SELECTION  (3) NESTED IF ELSE
A nested if-else statement is a conditional
structure where one if or else block contains
another if-else statement. This allows for more
complex decision-making by testing multiple
conditions in a hierarchical manner.

if (condition1)
{
// Code block if condition1 is true
if (condition2)
{
// Code block if condition2 is true
}
else
{
// Code block if condition2 is false
}
}
else
{
// Code block if condition1 is false
}
SELECTION (3) NESTED IF ELSE


SELECTION  (4) SWITCH
if-
else
Types of selection
structure
nested if-
else
switch
if-else-if

• 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
}

• 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.

• If expression was not equal
to constant1 it will be checked
against constant2. If it is equal to
this, it will execute statements2.

• 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 - switch
switch Flow
chart

• Example 1:
x
1
2
Other
value
Print
X is 1
X is 2
Value of x
unknown

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

• 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”
}

b) Flow
chart
iv) Selection -
switch

SUMMARY
if-else
Types of selection
structure
nested if- switch else
* Use an appropriate selection
control structure in problem
solving

1.2.3 LOOPING

SEQUENCE
Control
Structures
SELECTION LOOPING

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.

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

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

THE LOOPING CONTROL STRUCTURE:
1. The while
Construct

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

APPLYING ALGORITHM IN WHILE
CONSTRUCT
• Pseudocod
e
start
initialize counter
while (expression)
statement(s)
counter increment
end
1
2
4
3
* note: please refer to slide #4 for numbering details

APPLYING ALGORITHM IN WHILE
CONSTRUCT
• Flow
Chart
star
t
initializ
e
counte
r while
(expression
)
True
statem
ent(s)
counter
increment
False
en
d

THE COUNTER TABLE FOR WHILE
CONSTRUCT
counte
r
expressio
n
inpu
t
proces
s
outpu
t
counter
incremen
t
initial value
of
counter
condition
to test
IPO
analysis
increment to
modify the
loop
proces
s
outpu
t
i = i + 1
ample of while counter table:
i i <= 3
input

EXAMPLE 1: WHILE CONSTRUCT
• Problem Statement:
o Calculate the area of a rectangle for 3
times.
width
Height
• Remember to plan your algorithm.
o Do Problem Analysis.
o Transfer to Pseudocode or Flow
Chart.

i i <= 3 are
a
i = i + 1
while counter table
width,height area = width *
height
Problem Analysis:
Input: width, height
Process: area = width *
height Output: area

i i <= 3 width,height area = width * height area i = i + 1
1 T 2
2 T 3
3 T 4
Loop
terminate
Problem Analysis:
height Output: area
while counter
table

• Pseudocode
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
EXAMPLE 1: WHILE
CONSTRUCT
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

• Flow
Chart
EXAMPLE 1: WHILE
CONSTRUCT
star
t
(i <= 3)
True
width,
height
i = i + 1
i = 1
False
en
d
area = width
* height
are
a

THE LOOPING CONTROL STRUCTURE:
2. The do..while
Construct

THE DO..WHILE CONSTRUCT
• The do..while construct has the general form:
do
stateme
nt
while
(expressi
on);
• 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.

APPLYING ALGORITHM IN
DO..WHILE
CONSTRUCT
• Pseudocod
e
start
initialize
counter do
statement(s)
counter increment
while (expression)
end
1
2
4
3

APPLYING ALGORITHM IN DO..WHILE
CONSTRUCT
• Flow
Chart
star
t
True
initialize
counter
statement(s)
counter
increment
while
(expression
)
False
en

THE COUNTER TABLE FOR
DO..WHILE
CONSTRUCT
counter input process
output
counter
incremen
t
expressio
n
initial value
of
counter
condition
to test
IPO
analysis
increment to
modify the
loop
outpu
t
i = i + 1 i <= 3
ample of do..while counter table:
i input
process

EXAMPLE 2: DO..WHILE CONSTRUCT
times.
width
Height
Chart.

i width,heig
ht
i = i + 1 i <= 3
do..while counter
table
area = width * height
area
Problem Analysis:
height Output: area

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

02/10/1
• Pseudocod
e
start
EXAMPLE 2: DO..WHILE
CONSTRUCT
i = 1
2. do
3. input width, height
4.calculate area of
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

02/1 /
• Flow
Chart
EXAMPLE 2: DO..WHILE
CONSTRUCT star
t
(i <= 3)
True
False
en
d
i = 1
width, height
area = width
* height
area
i = i + 1

02/10/1
3. The for
Construct
THE LOOPING CONTROL
STRUCTURE:

* n0o2t/e1:0s/1ta2tement(s); which can be a block of
statements – more than 1 statement
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.

02/10/12
APPLYING ALGORITHM IN FOR
CONSTRUCT
• Pseudocode
2 1 4
3
start
for (initialize counter; expression; counter
increment)
statement(s)
; end

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
02/1th0/e12expression becomes false.
THE FOR LOOP IS EXECUTED AS
FOLLOWS:

APPLYING ALGORITHM IN FOR
CONSTRUCT
• Flow
Chart
star
t
True
statement(s
)
counter
increment
initializ
e
counte
r
False
(expressio
n)
en
d

THE COUNTER TABLE FOR FOR
CONSTRUCT
counte
r
expressio
n
inpu
t
proces
s
outpu
t
counter
incremen
t
initial value
of
counter
condition
to test
IPO
analysis
increment to
modify the
loop
proces
s
outpu
t
i = i + 1
ample of for counter table:
i i <= 3
input

EXAMPLE 3: FOR CONSTRUCT
times.
width
height
Chart.

i i <= 3 are
a
i = i + 1
for counter table
width,height area = width *
height
EXAMPLE 3: FOR CONSTRUCT
Problem Analysis:
height Output: area

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
EXAMPLE 3: FOR
CONSTRUCT
Problem Analysis:
height Output: area
for counter
table

EXAMPLE 3: FOR
CONSTRUCT
• Pseudocode
start
i = 1
2. for (i <= 3)
3. read width, height
4.calculate area of
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

• Flow
Chart
EXAMPLE 3: FOR
CONSTRUCT
star
t
(i <= 3)
True
width,
height
i = i + 1
i = 1
False
en
d
area = width
* height
are
a

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:
m
=
m
+
su su
num
tota
l
= tota
l
+ mark
s
2 1
2 1

Solving?
HOW TO APPLY ACCUMULATING IN
PROBLEM EXAMPLE 4: ACCUMULATING IN
SEQUENCE
STRUCTURE
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

HOW TO APPLY
ACCUMULATING IN
LOOPING?
Example 5: Accumulating in Looping
Structure
o Calculate the average of three
numbers.
Problem
Analysis:Accumulating Input:
num
Process: total = total +
num average = total / 3

EXAMPLE 5: ACCUMULATING IN LOOPING
Structure
Problem Analysis:
Input: num
Process: total = total +
num average = total / 3
Output: average
Using accumulating in while
construct (while counter
table)
total i i <=
3
num total = total +
num
i = i + 1 average = total /
3
averag
e
0 1 T 70 70 2
2 T 80 150 3
3 T 90 240 4
02/10/4
F Loop average = 240 / 3 80

PSEUDOCODE FOR ACCUMULATING IN WHILE
 initial value of total
 initial value of counter
condition to test
 IPO analysis
increment to modify
the loop
 Repeat step 3 – 6 until
expression is false
Construct
:
start
1. initialize total
total = 0
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

FLOW CHART FOR ACCUMULATING IN WHILE
CONSTRUCT:
(i <= 3)
True
num
en
d
total = total +
num
i = i + 1
start
total =
0
i = 1
False
average = total /
3
averag
e

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.

Problem solving and programming control structures.pptx

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Problem solving and programming control structures.pptx