Using a mask, multiple bits in a nibble, byte, words can be set either on, off or inverted from on to off (or vice versa) in a single bitwise operation.
More detail is in
https://en.wikipedia.org/wiki/Mask_(computing)
1) Masking bits to 1
To turn certain bits on, we need to use OR.
To make sure a bit is on, OR can be used as 1.
To make sure a bit is off, OR can be used as 0.
ex:
0000 1111
OR 0010 0010
------------
0010 1111
2) Masking bits to 0
To turn certain bits off, we need to use AND.
To make sure a bit is off, AND can be used as 0.
ex:
0000 1111
AND 0010 0010
-------------
0000 0010
3) Toggling bit values
If the original bit is 0, it returns 0 XOR 1 to 1.
If the original bit is 1, it returns 1 XOR 1 to 0.
EX:
0000 1111
XOR 0010 0010
-------------
0010 1101