In Unix, the root directory is located at a fixed place on the disk. When it is found, its inode is known. From the inode, the location on disk of the directory is found. When it is found its inode is given. When this is found, its inode is known and the file blocks are finally located.
Objects belong to one or more protection domains, and in each domain they give access rights.
Similarly, the printer device PRN does not grant delete access in this domain, and it cannot be deleted. On the other hand, it does grant write access, and so you can copy a file to PRN to send it to the printer. Given a particular pair, a list can be made of all files that allow operations to be carried out on them. Every process that runs with that value can access for reading that same set of files. Example Files that are readable by everyone belong to every protection domain for reading.