What is the difference between while used before loop and after loop?

Answer 1

In while loops (i.e while used before the body of the loop) the loop will continue to execute as long as the given condition is true. But if the condition is false initially then the while loop won't execute. However in a do while loop in which the condition is given after the body of the loop, even if the condition is false initially the loop still will be executed for one time. For example:

int a = 5;
while (a < 5) // condition is tested before loop body
{
cout << "Loop body";
}
cout << "Out of the loop";
return 0;

output :
Out of the loop

int a =5;
do
{
cout << "Loop body";
}
while(a<5); // Condition is tested after the loop body so it runs at least once
cout << endl << "Out of the loop";
return 0;

Output :
Loop body
Out of the loop