Read bit

[Supani harijanto]

How to read one bit in variable?

[GSontag]

AND is your best friend!
suppose you want to test the bit b
xxxxbxxx (your variable) apply a mask on it
00001000
AND both value you get
0000b000
so either b is 0 so the result is 0
or b is 1 so the result is not 0
result= value AND (1 << n) will test the nth bit of value (starting from 0 for low bit)

setting a bit to 0
xxxxbxxx
11110111 mask to use with AND

setting a bit to 1
xxxxbxxx
00001000 mask to use with OR

flipping a bit (0->1, 1->0) but don't know the the value
xxbxxxxx
00100000 mask to use with XOR

Hope this is clear.