< Computer Science Depart.
>
< Future Academy >
< Fall 2023 “Semester One”>
{ < Level 1>
< Week 4>
< Section 04>
Relational Operators
&
Loops
< Eng.Taghreed Salem >
... }
Relational Operators
• They are used in Conditions (Decisions / Selection)
• They are also used in Repetitions (Loops / Iterations)
• They have Yes / No answers , i.e., either true or
Relational Operators
> x is greater than y?
< x is less than y?
>= x is greater than or equal to y?
<= x is less than or equal to y?
Loops(Repetitions/iterations )
• A loop is a repetition control structure. It
causes a single statement or block of statements
{ to be executed repeatedly.
For example:
If we wish to read 100 numbers and compute the
average.
• Repetition statements in C++:
}
Counter–Controlled Repetition
For statement
(Counter–Based Repetition)
While statement
.. or ..
do..while statement
Sentinel–Controlled Repetition
Counter –Controlled Repetition
Defined repetition: Number of repetitions is known in advance.
An iteration=1 repetition
General forms of Repetition
Statements
Expression 1 initialization: (k=1)
We need : Expression 2 Continuation condition: (k<=10)
Expression 3 increment : (k=k+1)
For(Expression 1 ; Expression 2 ; Expression 3 )
{
Statement;
}
Expression 1 ; Expression1 ;
while (Expression 2 ) do
{ {
Statement; statement;
Expression
Expression 3 ; 3;
} } while (Expression 2) ;
Repetition Statements
(the for Loop )
for(initialization ; condition ; incrementation)
Repetition Statements
#include <iostream>
using namespace std;
int main()
{
int i;
for(i = 0; i < 5; i++) {
cout << " i = "<< i <<endl;
cout << "After Loop, i = " << i
<<" ";
}
return 0;
}
Repetition Statements
(While vs. Do-While Loops)
Notes About Expressions
• Off-by-One Error:
If you wrote counter < 10 instead counter <= 10, then the loop will be
executed only 9 times.
• Expressions can contain arithmetic expressions:
For example, If x = 2 and y = 10 ..
for ( j = x + y; j <= 4 * x* y ; j += y / x)
• Increment may be negative > decrement
Notes about the Expressions..
• If the loop-continuation is
initially false:
loop body will not be executed.
but, a do .. while’s body is executed at least once.
Notes about the Expressions..
An increment expression is exactly similar to a standalone
statement:
• counter = counter + 1;
• counter += 1;
• ++count;
• count++;
Thus, are all equivalent.
Notes about the Expression
for statements..
Both expression 1 and expression 3 are comma-separated lists:
for ( x = 0 , y = 0 ; x <= 10 ; x++ , y += 2 )
The commas as used here are comma operators ..
for statement … An Example
Expressions in a for statement’s header are optional:
You can omit:
Expression 1: if the control variable is initialized before using
the for statement.
Expression 2: C++ assumes that the condition is true >> infinite loop
Expression 3 : If the increment is in the for’s body, or if its not needed
for statement …
Examples of varying the control variable in a for statement:
Vary the control variable from 1 to 100 in increments of
1. for ( i = 1; i <= 100; i++ )
Vary the control variable from 7 to 77 in steps of 7.
for ( i = 7; i <= 77; i += 7 )
Vary the control variable from 20 to 2 in steps
of -2. for ( i = 20; i >= 2; i -= 2 )
Vary the control variable over the following sequence of values:
2, 5, 8, 11, 14, 17.
for ( j = 2; j <= 17; j += 3 )
Trace this code segment
Int count ;
count = 2;
while (count > 0)
cout<< "\n" << count ;
count-- ;
cout<<"\n" <<“Done” ;
Output:
Trace this code segment
2
Int count ;
count = 2;
while (count > 0)
cout<< "\n" << count ;
count-- ;
cout<<"\n" <<“Done” ;
Output:
Trace this code segment
2
Int count ;
count = 2;
while (count > 0) True!
cout<< "\n" << count ;
count-- ;
cout<<"\n" <<“Done” ;
Output:
Trace this code segment
2
Int count ;
count = 2;
while (count > 0)
cout<< "\n" << count ;
count-- ;
}
2
cout<<"\n" <<“Done” ;
Output:
Trace this code segment
2
Int count ;
1
count = 2;
while (count > 0)
cout<< "\n" << count ;
count-- ;
}
2
cout<<"\n" <<“Done” ;
Output:
Trace this code segment
2
Int count ;
1
count = 2;
while (count > 0) True!
{
cout<< "\n" << count ;
count-- ;
}
2
cout<<"\n" <<“Done” ;
Output:
Trace this code segment
2
Int count ;
1
count = 2;
while (count > 0)
cout<< "\n" << count ;
count-- ;
}
2
cout<<"\n" <<“Done” ; 1
Output:
Trace this code segment
2
Int count ;
1
count = 2;
0
while (count > 0)
cout<< "\n" << count ;
count-- ;
}
2
cout<<"\n" <<“Done” ; 1
Output:
Trace this code segment
2
Int count ;
1
count = 2;
0
while (count > 0) False!
{
cout<< "\n" << count ;
count-- ;
}
2
cout<<"\n" <<“Done” ; 1
Output:
Trace this code segment
2
Int count ;
1
count = 2;
0
while (count > 0)
cout<< "\n" << count ;
count-- ;
}
2
cout<<"\n" <<“Done” ; 1
Done
Output:
Calculate the sum of numbers from 1 to 2:
{
int sum = 0;
int i;
for ( i = 1; i <= 2 ; i++)
{
sum = sum + i; // or sum+=i;
}
cout<<“The sum is :”<<sum;
return 0;
} Note: i++ is the same as
i = i + 1, and as i += 1.
sum i
0
{
int sum = 0;
int i;
for ( i = 1; i <= 2 ; i++)
{
sum = sum + i; // or sum+=i;
}
Output
cout<<“The sum is :”<<sum;
return 0;
}
sum i
0 1
{
int sum = 0;
int i;
for ( i = 1; i <= 2 ; i++)
{
sum = sum + i; // or sum+=i;
}
Output
cout<<“The sum is :”<<sum;
return 0;
}
sum i
0 1
{
int sum = 0;
int i; True
for ( i = 1; i <= 2 ; i++)
{
sum = sum + i; // or sum+=i;
}
Output
cout<<“The sum is :”<<sum;
return 0;
}
sum i
0 1
{
int sum = 0; 1
int i; True!
for ( i = 1; i <= 2 ; i++)
{
sum = sum + i; // or sum+=i;
}
Output
cout<<“The sum is :”<<sum;
return 0;
}
sum i
0 1
{
int sum = 0; 1 2
int i;
for ( i = 1; i <= 2 ; i++)
{
sum = sum + i; // or sum+=i;
}
Output
cout<<“The sum is :”<<sum;
return 0;
}
sum i
0 1
{
int sum = 0; 1 2
int i; True!
for ( i = 1; i <= 2 ; i++)
{
sum = sum + i; // or sum+=i;
}
Output
cout<<“The sum is :”<<sum;
return 0;
}
sum i
0 1
{
int sum = 0; 1 2
int i; True!
3
for ( i = 1; i <= 2 ; i++)
{
sum = sum + i; // or sum+=i;
}
Output
cout<<“The sum is :”<<sum;
return 0;
}
sum i
0 1
{
int sum = 0; 1 2
int i; 3 3
for ( i = 1; i <= 2 ; i++)
{
sum = sum + i; // or sum+=i;
}
Output
cout<<“The sum is :”<<sum;
return 0;
}
sum i
0 1
{
int sum = 0; 1 2
int i; False!
3 3
for ( i = 1; i <= 2 ; i++)
{
sum = sum + i; // or sum+=i;
}
Output
cout<<“The sum is :”<<sum;
return 0;
}
sum i
0 1
{
int sum = 0; 1 2
int i; 3 3
for ( i = 1; i <= 2 ; i++)
{
sum = sum + i; // or sum+=i;
}
Output
cout<<“The sum is :”<<sum;
return 0;
} The sum is : 3
The Sum of Even Values using a for Statement
..Sum the Even values from 2 to 100 ..
int sum = 0; int number;
for ( number = 2; number <= 100; number += 2 )
{
sum += number;
}
cout<<"Sum is :" <<sum ;
Print the iterations using
the 3 ways
#include <iostream>
using namespace std; // Do-While Loop
int main() { cout << "\nDo-While Loop:" <<
// For Loop endl;
cout << "For Loop:" << endl;
int k = 0;
for (int i = 0; i < 5; i++) {
do {
cout << "Iteration " << i + 1
<< endl;
cout << "Iteration " << k +
} 1 << endl;
k++;
// While Loop } while (k < 5);
cout << "\nWhile Loop:" << endl;
int j = 0; return 0;
while (j < 5) { }
cout << "Iteration " << j + 1
<< endl;
j++;
}
Write a C++ program to PRINT the ASCII TABLE/CHART
{ ..
“The more you practice
the more you get”
Taghreed Salem
} ..
Thanks!
Do you have any questions?
You can contact me on:
Taghreed.salem@fa-hists.edu.eg
