Code:
if( (p1_wheel & 0xC0) == 0xC0 )
"&" is the "bitwise AND" operator. that means that it looks at individual bits of a value, and does an AND operation. AND is defined as follows: true if both inputs are true, otherwise false. a logic table:
0, 0 = 0
1, 0 = 0
0, 1 = 0
1, 1 = 1
so as you can see, it will only return 1's in the places where both numbers have ones. thus, it will only return all of the bits of one value if the same bits are 1's in the other value. the if statement essentially checks to see that all of the bits that are 1 in 0xC0 are also 1 in p1_wheel. replace 0xC0 with whatever "bitmask" (set of bits) you want to test as being 1.