The return value specifies the status of the given virtual key, as follows:

If the high-order bit is 1, the key is down; otherwise, it is up.

If the low-order bit is 1, the key is toggled. A key, such as the caps lock key, is toggled if it is turned on. The key is off and untoggled if the low-order bit is 0. A toggle key's indicator light (if any) on the keyboard will be on when the key is toggled, and off when the key is untoggled.


I copied the answer from MSDN

High-order bit=1 means negative
High-order bit=0 means positive