1. Intro to Programming Week # 4 Switch Statement Lecture # 7
Department of Computer Science & Engineering
Air University
Intro to Programming Week # 4 Switch Statement Lecture # 7
By: Saqib Rasheed

2. CS 161 Intro To Programming
Quiz
Time [20 Mins] Marks[10] Write a program to check whether a triangle is valid or not, when the three angles of the triangle are entered through the keyboard. A triangle is valid if the sum of all the three Angles is equal to 180 degrees
CS 161 Intro To Programming

3. CS 161 Intro To Programming
switch statement
The control statement that allows us to make a decision from the number of choices is called a switch statement
CS 161 Intro To Programming

4. CS 161 Intro To Programming
switch statement
switch ( variable name ) { case ‘a’ : statements; case ‘b’ : statements; case ‘c’ : statements; … }
CS 161 Intro To Programming

5. CS 161 Intro To Programming
switch statement
switch ( grade) { case ‘A’ : cout << “ Excellent ” ; case ‘B’ : cout << “ Very Good ” ; case ‘C’ : … … }
CS 161 Intro To Programming

6. CS 161 Intro To Programming
switch statement
case ‘A’ : cout << “ Excellent ” ; … …
CS 161 Intro To Programming

7. CS 161 Intro To Programming
Example
switch ( grade) { case ‘A’ : cout << “ Excellent ” ; case ‘B’ : cout << “ Very Good ” ; case ‘C’ : cout << “Good ” ; case ‘D’ : cout << “ Poor ” ; case ‘F’ : cout << “ Fail ” ; }
CS 161 Intro To Programming

8. CS 161 Intro To Programming
break;
CS 161 Intro To Programming

9. CS 161 Intro To Programming
Example
char grade; cin>>grade; switch ( grade ) { case ‘A’ : cout << “ Excellent ” ; break ; case ‘B’ : cout << “ Very Good ” ; break ; case ‘C’ : cout << “Good ” ; break ; case ‘D’ : cout << “ Poor ” ; break ; case ‘F’ : cout << “ Fail ” ; }
CS 161 Intro To Programming

10. CS 161 Intro To Programming
default :
default : cout << “ Please Enter Grade from ‘A’ to ‘D’ or ‘F’ “ ;
CS 161 Intro To Programming

11. Flow Chart of switch statement
switch (grade)
case ‘A’ :
Display
“Excellent”
case ‘B’ :
Display
“Very Good” …
Default :
“……..”
CS 161 Intro To Programming

12. CS 161 Intro To Programming
Example
int grade; cin>>grade; switch ( grade ) { case 1 : cout << “ Excellent ” ; break ; case 2 : cout << “ Very Good ” ; break ; case 3 : cout << “Good ” ; break ; case 4 : cout << “ Poor ” ; break ; case 5 : cout << “ Fail ” ; }
CS 161 Intro To Programming

13. CS 161 Intro To Programming
Example # 1
int i = 2 ; switch ( i ) { case 1 : cout<<"I am in case 1 \n"; break; case 2 : cout<<"I am in case 2 \n"; break; case 3 : cout<<"I am in case 3 \n"; break; default : cout<<"I am in default \n"; }
Output
I am in case 2
CS 161 Intro To Programming

14. CS 161 Intro To Programming
if-else Switch
switch (x) {
case 1:
cout << "x is 1";
break;
case 2:
cout << "x is 2";
default:
cout << "value of x unknown"; }
if (x == 1) { cout << "x is 1"; } else if (x == 2) cout << "x is 2"; else cout << "value of x unknown";
CS 161 Intro To Programming

15. switch Versus if-else Ladder
There are some things that you simply cannot do with a switch. These are:
A float expression cannot be tested using a switch
Cases can never have variable expressions (for example it is wrong to say case a +3 :
Multiple cases cannot use same expressions. Thus the following switch is illegal:
switch ( a ) {
case 3.2 :
case 4:
case :
case 4: :
CS 161 Intro To Programming

16. CS 161 Intro To Programming
Example # 2
int day;
cout<<"Eneter Day Number";
cin>>day;
switch (day) {
case 1 : cout << "\nSunday";
break;
case 2 : cout << "\nMonday";
case 3 : cout << "\nTuesday";
case 4 : cout << "\nWednesday";
case 5 : cout << "\nThursday";
case 6 : cout << "\nFriday";
case 7 : cout << "\nSaturday";
default : cout << "\nNot an allowable day number"; }
CS 161 Intro To Programming

17. CS 161 Intro To Programming
switch (day) { case 1 : case 7 : cout << "This is a weekend day"; break; case 2 : case 3 : case 4 : case 5 : case 6 : cout << "This is a weekday"; default : cout << "Not a legal day"; break; }
Break 1
Break 2
CS 161 Intro To Programming

18. CS 161 Intro To Programming
Example # 3
char ch ; cout<< "Enter any of the alphabet a, b, or c "; cin>>ch; switch ( ch ) { case 'a' : case 'A' : cout<<"a is an apple" ; break ; case 'b' : case 'B' : cout<<"b as in brain"; break ; case 'c' : case 'C' : cout<<"c as in cookie"; break ; default : cout<<"wish you knew what are alphabets" ; }
CS 161 Intro To Programming

19. Is switch a replacement for if?
Yes and no. Yes, because it offers a better way of writing programs as compared to if, and no because in certain situations we are left with no choice but to use if. The disadvantage of switch is that one cannot have a case in a switch which looks like:
case i <= 20 :
CS 161 Intro To Programming

20. switch works faster than an equivalent if-else ladder.
compiler generates a jump table for a switch during compilation
during execution it simply refers the jump table to decide which case should be executed .
if-elses are slower because they are evaluated at execution time
CS 161 Intro To Programming

21. CS 161 Intro To Programming
Question # 1
Make a calculator using switch statement
It should take two numbers from user.
Ask the user the function to perform
Display the result
CS 161 Intro To Programming

22. CS 161 Intro To Programming
Question # 2
Que
Write a menu driven program program in C++
using switch statement that contain option as
under.( The Menu should )
Enetr 1--> To Find Largest Number Among Three Variables.
Enetr 2--> To Find ODD or EVEN
Enetr 3--> To Find Condition of Water
Enetr 4--> To Find Grade Of Student
CS 161 Intro To Programming

23. CS 161 Intro To Programming
Question # 2 (Code)
#include<iostream.h> Void main () { int option; cout<<"\n\t\tEnter the option\n"; cout<<"Enetr 1--> To Find Largest Number Among Three Variables.\n"; cout<<"Enetr 2--> To Find ODD or EVEN\n"; cout<<"Enetr 3--> To Find Condition of Water\n"; cout<<"Enetr 4--> To Find Grade Of Student\n"; cin>>option;
CS 161 Intro To Programming

24. CS 161 Intro To Programming
Question # 2 (Code)
switch (option) { case 1: int a,b,c, larg; cout<<"Enter First Integer="; cin>>a; cout<<"Enter Second Integer="; cin>>b; cout<<"Enter Third Integer="; cin>>c;
CS 161 Intro To Programming

25. CS 161 Intro To Programming
Question # 2 (Code)
if (a > b)
larg = a;
else
larg = b;
if (larg > c )
cout<<"Largest is ="<<larg<<endl;
cout<<"Largest is ="<<c<<endl;
break;
CS 161 Intro To Programming

26. CS 161 Intro To Programming
Question # 2 (Code)
case 2: int value; cout<<"Enter an Interger value "; cin>>value; if (value % 2 == 0) cout<<"Your number is EVEN\n"; else cout<<"Your number is ODD\n"; break;
CS 161 Intro To Programming

27. CS 161 Intro To Programming
case 3: int t; cout<<"Temperature Less than 0 = ICE \n" <<"Temperature Greater than 0 & " <<"Temperature Less than 100 = Water\n" <<"Temperature Greater than 100 = STEAM\n"; cout<<"\n\n\t\tPlease enter the Temperature="; cin>>t; if ( t <= 0 ) cout<<"Form of water is \"ICE\""<<endl; else if( t > 0 && t < 100 ) cout<<"Form is \"WATER\"\n"; else if ( t >= 100 ) cout<<"Form of water is \"steam\"\n“; break;
CS 161 Intro To Programming

28. CS 161 Intro To Programming
case 4:
int grade;
cout<<"Enter the grade of student=";
cin>>grade;
if ( grade >= 90 )
cout<< " Grade A \n";
else if (grade >= 80 )
cout<<" Grade B \n";
else if ( grade >=70 )
cout<<" Grade C \n";
else if (grade >=60)
cout<<" Grade D \n";
CS 161 Intro To Programming

29. CS 161 Intro To Programming
else { cout<<" Grade F \n"; cout<<" You have to take the classes again\n"; cout<<" Work Hard To Get Good Grade\n"; } break; default: cout<<"You Entered Invalid Option\n"; cout<<"Enetr A Valid Option\n"; } //End Of Switch } //End Of Main
CS 161 Intro To Programming