Over on CF-Talk today, Dennis Powers had a problem with selecting the correct records when dealing with bit flags. I'm a big fan of flags and bitwise math, so I jumped in and helped him out. I had to think about the operations a bit (no pun intended) too long, so I decided to drop myself a note as a refresher.

When dealing with bit flags, here is a handy cheatsheet:

myMask = 1st and 8th flags set (10000001 -> 2^7 + 2^0 -> 129)

myVar & myMask = myMask (All masked flags are set)
myVar & myMask > 0 (At least one masked flag is set)
myVar & myMask = 0 (None of the masked flags are set)
myVar = myMask  (All masked flags set, all other flags not set)

Happy masking!