$e0 = binary 11100000
$f0 = bin 11110000

logical function AND (&) goes like this

a b a&b
0 0 0
0 1 0
1 0 0
1 1 1

logical bitwise function OR (|) goes like this
a b a&b
0 0 0
0 1 1
1 0 1
1 1 1

masking clearing and setting bit/s in a var can be accomplished this way

eg if a = %11111111 (255 or $ff)

then a&$e0= %11100000

then a | 12 = %11101100

see bitwise in book