Q. We have an OS (operating system) for a machine that uses base and limit registers however we have modified the machine to provide a page table. Can the page tables be set up to replicate base and limit registers? How can they be or else why can they not be?

Answer: The page table is able to be set up to simulate base and limit registers provided that the memory is allocated in fixed-size segments. In this way the base of a segment can be entered into the page table and the valid or invalid bit used to indicate that portion of the segment as resident in the memory. There will be a few problems with internal fragmentation.