floating point in C++

Sometimes floating point might catch you in the least expected place:

See the innocent looking code below:

double x; cin >> x;
cout << int(100*x) << endl;

On some machines, if x is 0.70, then you will get 69 instead of 70. I guess this has something to do with the precision of double, as some decimal floating point does not have an exact binary representation. So the double is read and stored in an approximate value. Then the cast to int results in something like 69.999999999999.