1. LESSON 4 Decision Control Structure

2. Decision Control Structures
if statement
if-else statement
nested if-else statement
switch-case statement

3. if statement
if (condition) {
statement1;
statement2; }

4. if Statement Sample #include <iostream> #include <conio.h>
using namespace std;
int main() {
int grade = 77;
if (grade >= 67)
cout<<“You passed C++”; }
getch();
return 0;
You passed C++

5. if Statement Sample #include <iostream> #include <conio.h>
using namespace std;
int main() {
int grade = 50;
if (grade >= 67)
cout<<“You passed C++”; }
getch();
return 0;

6. If-else statement if (condition) { statementA1; statementA2; } else
statementB1;
statementB2;

7. If-else Statement Sample
#include <iostream>
#include <conio.h>
using namespace std;
int main( ) {
int x= 6;
int y= 2;
if (x > y)
cout<<“x is greater than y \n”;
else
cout<<“y is greater than x \n”;
getch();
return 0; }
x is greater than y

8. If-else Statement Sample
#include <iostream>
#include <conio.h>
using namespace std;
int main( ) {
int x= 4;
int y= 8;
if (x > y)
cout<<“x is greater than y \n”;
else
cout<<“y is greater than x \n”;
getch();
return 0; }
y is greater than x

9. Nested if Statement if (condition1) { statementA1; statementA2; }
else if (condition2)
statementB1;
statementB2;

10. Nested if Statement Sample
#include <iostream>
#include <conio.h>
using namespace std;
int main( ) {
int x= 6;
int y= 2;
if (x > y)
cout<<“x is greater than y \n”;
else if (y<x)
cout<<“y is greater than x \n”;
else
cout<<“x and y are equal \n”;
getch();
return 0; }
x is greater than y

11. Nested if Statement Sample
#include <iostream>
#include <conio.h>
using namespace std;
int main( ) {
int x= 2;
int y= 6;
if (x > y)
cout<<“x is greater than y \n”;
else if (x<y)
cout<<“y is greater than x \n”;
else
cout<<“x and y are equal \n”;
getch();
return 0; }
y is greater than x

12. Nested if Statement Sample
#include <iostream>
#include <conio.h>
using namespace std;
int main( ) {
int x= 6;
int y= 6;
if (x > y)
cout<<“x is greater than y \n”;
else if (y<x)
cout<<“y is greater than x \n”;
else
cout<<“x and y are equal \n”;
getch();
return 0; }
x and y are equal

13. The switch-case Statement
Clean way to implement multi-way selection
The switch statement evaluates an expression, then attempts to match the result to one of several possible cases
The match must be an EXACT match.

14. The switch - case syntax
The general syntax of a switch statement is:
switch (expression) {
case constant1 :
statement-list1
break;
case constant2 :
statement-list2
break ….
default:
statement-list3 }

15. switch Example int day =3; switch ( day ) {
case 1: cout <<“Monday” ;
break ;
case 2: cout << “Tuesday”) ;
case 3: cout << “Wednesday” ;
case 4: cout << “Thursday” ;
case 5: cout << “Friday” ;
default: cout << “Invalid day.” ; }

16. switch Example int day =5; switch ( day ) {
case 1: cout <<“Monday” ;
break ;
case 2: cout << “Tuesday”) ;
case 3: cout << “Wednesday” ;
case 4: cout << “Thursday” ;
case 5: cout << “Friday” ;
default: cout << “Invalid day.” ; }

17. switch Example int day =6; switch ( day ) {
case 1: cout <<“Monday” ;
break ;
case 2: cout << “Tuesday”) ;
case 3: cout << “Wednesday” ;
case 4: cout << “Thursday” ;
case 5: cout << “Friday” ;
default: cout << “Invalid day.” ; }

18. To Switch or not to Switch
The expression of a switch statement must result in an integral type, meaning an integer (whole number) or a char ONLY
It cannot be a floating point value (float or double)
You cannot perform relational checks with a switch statement

19. To Switch or not to Switch
The expression of a switch statement must result in an integral type, meaning an integer (whole number) or a char ONLY
char letter =‘b’;
switch ( letter ) {
case ‘a’: cout<<“A”;
break ;
case ‘b’: cout<<“B”;
default: cout<< “Invalid Input.”; }

20. To Switch or not to Switch
It cannot be a floating point value (float or double)
float x =3.14;
switch ( x ) {
case 3.14: cout<<“A” ;
break ;
case 3.16: cout<<“B” ;
default: cout<<“Invalid Input.”; }

21. To Switch or not to Switch
You cannot perform relational checks with a switch statement
int x =123;
switch ( x ) {
case x>5: cout <<“A” ;
break ;
case x>4: cout<<“B” ;
default: cout<< “Invalid Input.”; }