while

while (ch != 'Q') {
   process();
   cin >> ch;
}

while is more intuitive than for in some cases but you have to initialize variables separately. Compare:

for (double x = 100; x > 2; x = sqrt(x)) 
    cout << x << endl;
  
double x = 100;
while (x > 2) {
    cout << x << endl;
    x = sqrt(x);
}

• continue statements are not-so-great programming style but may be convenient in some cases
• break statements can often be avoided by using the do {...} while(condition) construct instead.