S_FALSE top-level constant
Some methods use S_FALSE to mean, roughly, a negative condition that is not a failure. It can also indicate a "no-op"—the method succeeded, but had no effect. For example, the CoInitializeEx function returns S_FALSE if you call it a second time from the same thread. If you need to differentiate between S_OK and S_FALSE in your code, you should test the value directly, but still use FAILED or SUCCEEDED to handle the remaining cases.
const S_FALSE = 1;