Question

I always get confused when I am about to use a bit map to store multiple flags. For example, if there are 10 possible properties for an object (all Yes or No), I use an unsigned int and the first 10 bits (from LSB) based on the properties. Now how to set and unset a particular bit and also how to check if a bit is set or not?

If I want to unset the 5th bit, I use:
bitand (flag, 2^5 – 1)

But I am not clear on what to use to check if 5th bit is set or not.

Answer 1

check if the n^th bit is set:

(flags & (1 << n)) != 0

set the n^th bit:

flags |= (1 << n)

clear the n^th bit:

flags &= ~(1 << n)

toggle the n^th bit:

flags ^= (1 << n)