[eblack10]

What are the contents of register al on and intel processor after these instructions?

mov al, 01010101b
and al, 00001111b
or al, 11110000b

[xpi0t0s]

This isn't difficult. Where are you stuck? Do you understand what AND and OR do? (Presumably not, otherwise finding the answer would be trivial.)
Truth tables for AND and OR:
AND:
a b x
0 0 0
0 1 0
1 0 0
1 1 1

OR:
a b x
0 0 0
0 1 1
1 0 1
1 1 1

and these operations are performed on every bit. So, taking them right to left, 1 and 1 is 1, 0 and 1 is 0 etc, so the result is xxxxxx01; we then OR that with 11110000 which gives us xxxxxx01. You can fill in the x's now you know what to do.