Why does my loop not work as I am expecting?

Question

I have been learning c++ for about a week now, and I thought I had everything under control, but apparently not. I was mid program, and decided to hit run just to see how things were looking. The program runs, but never ends. I was expecting it to at least print the first cout statement.

#include <iostream>
using namespace std;

int main()
{
    int floors, rooms, i = 0;
    cout << "floors: "; cin >> floors;
    while (floors > i) 
    {
        cout << "rooms: "; cin >> rooms;
        ++i;
    }
}

OP appears to have vanished but check out http://stackoverflow.com/a/33691587/560648 — Lightness Races in Orbit, Jun 30 '16 at 10:29
_program runs, but never ends_ what do you exactly mean here? are you seeing some output window? If yes, what is shown in that? — Vineet Kumar, Jun 30 '16 at 12:55

score 2 · Accepted Answer · answered Jun 30 '16 at 10:13

You did not "flush your output". Depending upon various settings at various levels of abstraction, the floors: prompt then may not be displayed until there's also more output to go along with it.

Your program, then, is waiting for input before you are visibly prompted for it.

Add << flush to your cout statement to ensure that the text is shown on the screen:

You should also verify that the input to cin was successful, otherwise floors has an indeterminate value and your loop very well may go on "for ever".

cout << "floors: " << flush;
if (!(cin >> floors))
  throw std::runtime_error("Value provided for 'floors' could not be read into an int!");

Shouldn't `cin` and `cout` be tied by default, omitting the need for an explicit flush, unless you have explicitly changed the tying in your code? — MicroVirus, Jun 30 '16 at 10:18

Why does my loop not work as I am expecting?

1 Answers1