A question about while loop

I thought I understood while and for loops quite well. However, recently I saw a program which had a while loop which only contained:

while (1)
Can anyone please help me understand as to what condition is being tested here for being false of true? Thanks a lot.

Arooj

while(1) == while(true)

I have barely used it, actually come to think of it, I don't think I ever have. But it could be used to show infinite loops.

1 == true

Thanks Alpha, if it is an infinite loop, then how does the program terminate. Actually I had to write a program which keeps on taking input until it encounters 2 successive instances of zeros. This is how I wrote it. Tell me if this is the correc way.

void ()
{
int num1, num2;
cout << "Enter a digit: ";
cin >> num1;
cout << "Enter a digit: ";
cin >> num2;
while (1) {
if (num1 == 0 && num2 == 0)
break;
cout << "Enter a digit: ";
cin >> num1;
if (num1 == 0 && num2 == 0)
break;
cout << "Enter a digit: ";
cin >> num2;
}

}

Can I instead write:
while (num1 != 0 && num2 != 0)
instead? I hope I made my problem clear. Thanks

then it will loop while num1 and num2 does not equal 0...so it will loop forever until num1 and num2 equal to zero...

Code:

---

    int num1,num2;
    cin >> num1 >> num2;
    while(num1!=0 && num2!=0) {
        num1 = num2;
        cin >> num2;
        if(!cin.good()) {
            cerr << "invalid input (expecting digit)" << endl;
            break; // or throw something
        }
//      do something with num1 & num2
    }

---

The previous code would fail on 5 0 0, assuming you wanted to stop on those consecutive zeros.

Thanks a lot. Actually program only checks 2 separate inputs to make sure both are not zeros. Thanks again.
Arooj