This include the conditional structure used in c language.

1. Programming Fundamentals
SHAHBAZ NAZEER
Control Structure

2. Books
 Deitel & Deitel :– C++ How to Program
 Robert Lafore : Object-Oriented Programming in C++
 IT Series : Object Oriented Programming Using C++
 shahabaznazeer@gcuf.edu.pk

3. Control Structures
 Control Structures are just a way to specify flow of control in programs.
 Any algorithm or program can be more clear and understood if they
use self-contained modules called as logic or control structures.
 It basically analyzes and chooses in which direction a program flows
based on certain parameters or conditions.
 There are four basic types of logic, or flow of control, known as:
1. Sequence logic, or sequential flow
2. Selection logic, or conditional flow
3. Iteration logic, or repetitive flow
4. Function Call

4. 1. Sequential Logic / Sequential Flow
 In Sequential logic/flow, statements are executed in the
same order in which they are specified in the program.
 Control moves from one statement to another statement in
a logical sequence.
 All statements are executed exactly once.
 It means that no statement is skipped or repeated more than one
time.
 Note : All the Programs covered in previous lectures are the
example of sequential logic.
Statement 1
Statement 2
Statement 3
Entry
End

5. 2. Selection logic, or conditional flow
 A Selection Structure selects a statement or block of statements to
execute on the basis of a condition.
 Statement(s) are executed or ignored on the basis of a condition.
 Statement(s) are executed if the condition is True.
 Statement(s) are ignored if the condition is False.

7. If statement
 if statement is the most simple decision making statement.
 It is used to decide whether a certain statement or block of
statements will be executed or not
 i.e if a certain condition is true then a block of statement is executed
otherwise not.
Syntax
if(condition)
{
// Statements to execute
// if condition is true
}

8. If statement - Example
 Write a program
 that input two numbers
 and validates that both are
equal.
#include "iostream"
using namespace std;
int main()
{
int num1 , num2;
cout<<"Enter First Number : ";
cin>> num1;
cout<<"Enter Second Number : ";
cin>> num2;
if ( num1 == num2 )
{
cout<<"Both Numbers are equal "<<endl;
}
cout<<"End of Program ! ";
return 1;
}

9. If – else statement
 The if statement alone tells us that if a condition is true it will
execute a block of statements and if the condition is false it won’t.
 But what if we want to do something else if the condition is false.
 Here comes the else statement. We can use the else statement
with if statement to execute a block of code when the condition is
false.
 Syntax
if (condition)
{
// Executes this block if condition is true
} else
{
// Executes this block if // condition is false
}

10. If – else statement - Example
 Write a program which input marks of a student
 And decides whether the student is Pass or Fail
 Marks equal or above 40 is considered as pass.
 Marks below 40 is considered as Fail.
#include "iostream"
using namespace std;
int main()
{
int marks;
cout<<"Enter Marks of the Student : ";
cin>> marks;
if ( marks >= 40 )
{
cout<<"Student is Pass !"<<endl;
}
else
{
cout<<"Student is Fail !"<<endl;
}
cout<<"End of Program ! ";
return 1;
}

11. Conditional or Ternary Operator (?:)
 The conditional operator is kind of similar to the if-else statement
 it does follow the same algorithm as of if-else statement
 but the conditional operator takes less space
 and helps to write the if-else statements in the shortest way possible.
variable = Expression1 ? Expression2 : Expression3
if( expression1)
{
variable = expression2;
}
else
{
variable = expression3;
}

12. Conditional or Ternary Operator (?:)
 // C++ program to find largest among two numbers using ternary operator
1. #include <iostream>
2. using namespace std;
3. int main()
4. {
5. int n1 = 5, n2 = 10, max;
6. max = (n1 > n2) ? n1 : n2;
7. cout << "Largest number = " << max;
8. return 1;
9. }
variable = Expression1 ? Expression2 : Expression3
If ( n1 > n2 )
{
max =
n1;
} else
{
max =
n2;

13. Nested if statement
 A nested if in is an if statement that is the target of another if
statement.
 Nested if statements means an if statement inside another if
statement. we can place an if statement inside another if
statement.
 Syntax
if (condition1)
{
// Executes when condition1 is true
if (condition2) {
// Executes
when condition2 is true
}
}

14. Multi-if or if-else-if statement
 A user can decide among multiple options.
 The if statements are executed from the top down.
 As soon as one of the conditions controlling the if is true, the
statement associated with that if is executed
 and the rest of the else-if statements are bypassed.
 If none of the conditions are true, then the final else statement will
be executed.
 Syntax
if (condition1)
// Executes when condition 1 is true
else if (condition2)
// Executes when condition 2 is true
…..
…
else
// Executes when None of above is true

15. Multi-if or if-else-if statement
- Example
 Write a program which input marks of a student
 And decides Grade of the student
1. Marks equal or above 64 considered as A Grade.
2. Marks equal or above 52 considered as B Grade.
3. Marks equal or above 40 considered as C Grade.
4. Marks equal or above 24 considered as D Grade.
5. Marks Less than 24 considered as F Grade.
#include "iostream"
using namespace std;
int main()
{
int marks;
cout<<"Enter Marks of the Student : ";
cin>> marks;
if ( marks >= 64 )
cout<<“A Grade !"<<endl;
else if ( marks >= 52 )
cout<<“B Grade !"<<endl;
else if ( marks >= 40 )
cout<<“C Grade !"<<endl;
else if ( marks >= 24 )
cout<<“D Grade !"<<endl;
else
cout<<"Student is Fail !"<<endl;
cout<<"End of Program ! ";
return 1;
}

16. #include "iostream"
using namespace std;
int main()
{
int marks;
cout<<"Enter Marks of the Student : ";
cin>> marks;
if ( marks >= 64 )
cout<<“A Grade !"<<endl;
else if ( marks >= 52 )
cout<<“B Grade !"<<endl;
else if ( marks >= 40 )
cout<<“C Grade !"<<endl;
else if ( marks >= 24 )
cout<<“D Grade !"<<endl;
else
cout<<"Student is Fail !"<<endl;
cout<<"End of Program ! ";
return 1;
}
Flow Chart
Program

17. Switch statement
 The switch statement is a multiday branch statement.
 It provides an easy way to dispatch execution to different parts of
code based on the value of the expression.
 Its an alternative to multi-if statement.
 Works with single expression.
 Single variable.
 Its Fast but not flexible.
switch (expression)
{
case value1:
statement1;
break;
case value2:
statement2;
break;
. .
default:

18. #include "iostream"
using namespace std;
int main()
{
char c;
cout<<"Enter Any Character : ";
cin>> c;
switch ( c )
{
case 'a':
cout<<c<<" is a vowel "<<endl;
break;
case 'e':
cout<<c<<" is a vowel "<<endl;
break;
case 'i':
cout<<c<<" is a vowel "<<endl;
break;
case 'o':
cout<<c<<" is a vowel "<<endl;
break;
case 'u':
cout<<c<<" is a vowel "<<endl;
break;
default:
cout<<c<<" = Not vowel "<<endl;
break;
}
Write a program which takes a character from user. It displays whether it’s a vowel or not.
vowels are = ‘a,e,i,o,u’
#include "iostream"
using namespace std;
int main()
{
char c;
cout<<“Enter Any Character : ";
cin>> c;
if ( c == 'a' )
cout<< c << “ is a
vowel !"<<endl;
else if ( c == ‘e' )
cout<< c << “ is a
vowel !"<<endl;
else if ( c == ‘i' )
cout<< c << “ is a
vowel !"<<endl;
else if ( c == ‘o' )
cout<< c << “ is a
vowel !"<<endl;
else if ( c == ‘u' )
cout<< c << “ is a
vowel !"<<endl;
else
multi – if structure Switch structure

19. Operators in C++

20. Logical Operators
Logical Operators in C++
Name Symbol Meaning
Not ! Logical inverse. True to false. False to true
AND && Logical Multiplication, Output is true if all inputs are true
OR || Logical Addition, Output is true if any inputs is true

21. Logical Operators

22. #include "iostream"
using namespace std;
int main()
{
char c;
cout<<"Enter Any Character : ";
cin>> c;
switch ( c )
{
case 'a':
cout<<c<<" is a vowel "<<endl;
break;
case 'e':
cout<<c<<" is a vowel "<<endl;
break;
case 'i':
cout<<c<<" is a vowel "<<endl;
break;
case 'o':
cout<<c<<" is a vowel "<<endl;
break;
case 'u':
cout<<c<<" is a vowel "<<endl;
break;
default:
cout<<c<<" = Not vowel "<<endl;
break;
}
Write a program which takes a character from user. It displays whether it’s a vowel or not.
vowels are = ‘a,e,i,o,u’
#include "iostream"
using namespace std;
int main()
{
char c;
cout<<“Enter Any Character : ";
cin>> c;
if ( c == 'a' )
cout<< c << “ is a
vowel !"<<endl;
else if ( c == ‘e' )
cout<< c << “ is a
vowel !"<<endl;
else if ( c == ‘i' )
cout<< c << “ is a
vowel !"<<endl;
else if ( c == ‘o' )
cout<< c << “ is a
vowel !"<<endl;
else if ( c == ‘u' )
cout<< c << “ is a
vowel !"<<endl;
else
multi – if structure Switch structure

23. Vowels using
Logical Operators
#include "iostream"
using namespace std;
int main()
{
char c;
cout<<“Enter Any Character : ";
cin>> c;
if ( c == 'a' || c == ‘e' || c == ‘i' || c == ‘o' || c == ‘u' )
cout<< c << “ is a vowel !"<<endl;
else
cout<<“Not a vowel !"<<endl;
}

24. Home Work
 Comparison between if and switch ?
 Practice a program on ASCII Table given on the next slide.
 Program should Input a character from user and display a message that it’s
a Number, Upper case Letter or Lower Case Letter or some other character.
 Number are digits between 0 to 9
 Upper case letter ( A to Z )
 Lower Case letter ( a to Z )
 Other symbol ( Any value other than above 3 categories. )

25. Programs for Practice.
1. Write a C++ program to check whether a given number is even or odd.
2. Write a C++ program to check whether a given number is positive or negative.
3. Write a C++ program to find whether a given year is a leap year or not.
4. Write a C++ program to read the age of a candidate and determine whether it is eligible for casting
his/her own vote. (18+ age is required to cast vote).
5. Write a C++ program which takes 3 numbers from user and find the largest of three numbers.
6. Write a program in C to read any day number in integer and display day name in the word.
7. Write a program in C to read any Month Number in integer and display the number of days for this month.