c++ Lecture 3

INSTRUCTOR:
ENGR. AFSHAN ASIM
CHAPTER # 3
LOOPS & DECISIONS

OBJECTIVES
• Relational operators.
• For Loop
• While Loop
• do while Loop
• Nested Loop

RELATIONAL OPERATORS
Operator Meaning
> Greater than
< Less than
== Equal to
!= Not equal to
>= Greater than or equal to
<= Less than or equal to

RELATIONAL OPERATORS (CONTD…)
int a=12; //assignment statement
int b=34; //assignment statement
(b<34) //false or 0
(b<=34) //true or 1
(a==12) //true or 1
(b!=35) //true or 1
(a>14) //false or 0
(a>=10) //true or 1

LOOPS
• Three kinds of loops
• For
• While
• Do-while

FOR LOOP
Syntax
•Single Statement Loop
for(variable initialization, condition, variable update)
statement; //executed if condition true
•Multi Statement Loop
for(variable initialization, condition, variable update)
{ //executed if condition true
statement1;
statement2;
}

FOR LOOP FLOW CHART
Initialization
Expression
Body of Loop
Increment
Expression
Test
Expression
Exit
false
True

FOR LOOP EXAMPLE
//single statement loop
#include<iostream>
using namespace std;
void main()
{
int i;
for(i=0;i<10;i++)
cout<<i<<endl;
system(“pause”);
}

FOR LOOP EXAMPLE
//multi statement loop
#include<iostream>
#include<iomanip>
int main()
{
int i;
for(i=0;i<10;i+=2)
{ //loop body starts
cout<<setw(4)<<i;
int j=i*i*i;
cout<<setw(6)<<j<<endl;
} //loop body ends
}

BLOCK & VARIABLE VISIBILITY
//multi statement loop
#include<iostream>
#include<iomanip>
int main()
{
int i;
for(i=0;i<10;i++)
cout<<setw(4)<<I;
int j=i*i*i;
cout<<setw(6)<<j<<endl;
} //loop body ends
cout<<j; //ERROR
}

FOR LOOP VARIATIONS
//increment expression variations
#include<iostream>
int main()
{
int i;
for(i=10;i>0;i--)
cout<<i;
cout<<endl;
} //loop body ends
}

FOR LOOP VARIATIONS
//variables defined in for statement
#include<iostream>
int main()
{
for(int i=0;i<10;i++)
cout<<i;
cout<<endl;
} //loop body ends
}

FOR LOOP VARIATIONS
//multiple initialization and increment
expressions
#include<iostream>
int main()
{
int i;
for(i=0,alpha=100;i<10;i++,alpha--)
……..
cout<<i;
cout<<endl;
} //loop body ends
}

TASK
What happens if you use for loop in the
following manner
•for(;;)
•for(;;);
(Submit your answers in the next class)

WHILE LOOP
Syntax
•Single Statement while Loop
while(test expression)
statement;
•Multi Statement while Loop
while(test expression)
{
Body of loop
}

WHILE LOOP FLOW CHART
Body of Loop
Test
Expression
Exit
false
True

WHILE LOOP EXAMPLE
#include<iostream>
int main()
{
int i=0;
while(i<10)
{
cout<<i<<endl;
i++;
}
}

DO WHILE LOOP
Syntax
do
{
Body of loop
}
while(test expression);

DO WHILE LOOP FLOW CHART
Body of Loop
Test
Expression
Exit
false
True

DO WHILE LOOP EXAMPLE
#include<iostream>
int main()
{
int i=0;
do
{
cout<<i<<endl;
i++;
} while(i<10);
}

NESTED LOOPS
• Loops inside another loop
• Example
{
for(int j=0;j<3;j++)
{
cout<<“Loop2”;
}
cout<<“nLoop1 “;
}
Inner Outer

NESTED LOOPS EXAMPLE
• Program to print the following
pattern
*
* *
* * *
* * * *

CONTD…
#include<iostream>
int main()
{
int num=1;
{
for(int j=0;j<num;j++)
{
cout<<“*”;
}
num++;
cout<<endl;
}
}

c++ Lecture 3

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c++ Lecture 3