1. Control Structures contd… Selection
Dr. Khizar Hayat
Associate Prof. of Computer Science

2. Multiway if…else Example
int main() { int day; cout<<"Enter the value for day"<<endl; cin>>day; if(day==1) cout << "Monday"; } else if(day==2) cout << “Tuesday"; if(day==3) cout << “Wednesday"; : if(day==7) cout << “Sunday"; cout << “Invalid input"; }….}} return(0);
Example
A program that inputs the day number and display the day name’ i.e.
1 for Monday
2 for Tuesday
3 for Wednesday …
7 for Sunday

3. Multiway if…else Example
int main() {
int day; cout<<"Enter the value for day"<<endl; cin>>day;
if(day==1)
cout << “Monday"; }
else if(day==2)
cout << “Tuesday";
else if(day==3)
cout << “Wednesday";
else if(day==4)
cout << “Thursday"; :
else if(day==7)
cout << “Sunday";
else
cout<<“Invalid Input";
return(0);
Example
A program that inputs the day number and display the day name’ i.e.
1 for Monday
2 for Tuesday
3 for Wednesday …
7 for Sunday

4. Multiway if…else Example
int main() { int day; cout<<"Enter the value for day"<<endl; cin>>day; if(day==1) cout << “Monday"; else if(day==2) cout << “Tuesday"; else if(day==3) cout << “Wednesday"; else if(day==4) cout << “Thursday"; else if(day==5) cout << “Friday"; else if(day==6) cout << “Satursday"; else if(day==7) cout << “Sunday"; else cout<<“Invalid Input"; return(0); }
Example
A program that inputs the day number and display the day name’ i.e.
1 for Monday
2 for Tuesday
3 for Wednesday …
7 for Sunday

5. The switch structure
switch(expression) //The term in ()is called the selector { case constant1: //constant1 also called label Statement(s); break; //needed to skip the rest of the cases case constant2: break; . default //optional part }

6. The switch
int main(void) { int day; cout << "Enter the day of the week between 1 and 7"; cin >> day; switch(day) case 1: cout << "Monday"; break; case 2: cout << "Tuesday"; case 3: cout << "Wednesday"; case 4: cout << "Thursday"; case 5: cout << "Friday"; case 6: cout << "Saturday"; case 7: cout << "Sunday"; default: //optional cout << “Invalid Input"; } return(0);
Example
A program that inputs the day number and display the day name’ i.e.
1 for Monday
2 for Tuesday
3 for Wednesday …
7 for Sunday

7. The switch structure The switch keyword.
Same as if…else if….else but limited;
Can only be used to compare an expression against constants
The case labels must have the same type as the selector
The case labels must all be different
You can associate more than one case labels with the same statement.
No need to use the delimiters ‘{}’ in case statement(s);
Omitting or forgetting break in a case is not a syntax error but a logical error.
It would take you to the subsequent case part
No need to write break in the default case but good for readability.

8. Problems
Write a program that takes a character input and tells you whether it is a vowel or not.
We may introduce getche() from conio.h
displaying a menu in a program.