ushort a, ushort b from ( ushort )( a | b ) to a with constant b

Question

I am working with data that is b and in more detail is described by a. Atleast that is how i understand it. Any further links to basic bitwise operations are appreciated. All objects i am looking at have b as 0x8000. I need to find out a from c.

I have:

ushort a
ushort b

a is from 2-5

b = 0x8000

ushort c = (ushort)( a | b )

can i and if yes how can i come from c to a?

I tried ( a & b ) but that leads me to b not a. I am realy stuck although i know it should be easy if possible if i would understand the operations.

Answer 1

Basically, it's c AND NOT b .

ushort a2 = (ushort) (c & ~b);

but only because a is from 2-5 and that is smaller than 0x8000.
When a and b start to overlap in bits you're stranded.

Answer 2

This will only work if a if smaller that b, which is true from the interval you give for a.

Both of these will work :

a = (ushort) (c & ~b)  
a = (ushort) c - b