[deathemperor]

let me try to explain.

like the above example:

32
16
8
4
2
1

this is 65, in your database you have a field called permissionwhatever to store that number (65), and if a usergroup has that value 65 it means they have full permission, each bit represent for a permission. if it's 64, then the value you don't have must be 1, 60 means without 1 and 4 and it cannot be any other number. so that's the way it realizes you don't have what permission.