The Do-While loop is essentially an inversion of the while loop.
Why is the Do-While loop important?
It executes the loop statements unconditionally the first time. It then evaluates the conditional expression specified before executing the statements again.
A sample code for the Do-While loop is attached below. I have also annotated the code so that a newbie can get a better understanding.
Situation #1: Do-while loop for the addition of 10 numbers put in by the user.
#include <iostream.h> #include <conio.h> void main() { clrscr(); #clear the screen int sum=0, counter=0, num; #counter represents the number of intergers the user has put in do { cout<<"\n\t Enter a number: "; cin>>num; sum=sum+num; counter++; #each time the user puts in a number, the counter increases by one. The ++ signifies an increment of 1 } while (counter<10); #the process of adding the numbers is follwed until counter<10. The program checks that the condition is met after adding the numbers once. cout<<"\n\t Sum= :<<sum; getch(); }
Complete code:
#include <iostream.h> #include <conio.h> void main() { clrscr(); int sum=0, counter=0, num; do { cout<<"\n\t Enter a number: "; cin>>num; sum=sum+num; counter++; } while (counter<10); cout<<"\n\t Sum= :<<sum; getch(); }
Situation #2: User enters a number and the program displays its factorial.
#include <iostream.h> #include <conio.h> void main() { clrscr(); int fact=1, num; cout<<"\n\t Enter a number: "; cin>>num; do { fact=fact*num; num=num-1; } while (num>0); cout<<"\n\t Factorial= "<<fact; getch(); }