Each segment has a name and a length. It differs from paging in that both the name and length of the segment are specified to calculate a physical address. The hardware for segmentation consists of a segment table which holds the base and limit of each segment. A physical address in calculated by adding the displacement to the base in the segment table for the desired segment provided this displacement is less than the limit of the segment. Paging Paging provides a solution to external fragmentation by allocating memory to a process wherever it is available.
Logical memory is broken into blocks of the same size called pages.
Logical addressing contains two parts. A page number and an offset into the page. A page table contains the base address of each page in physical memory. Illegal addresses are detected using a page table length register. Every logical address is verified to be less than the value held in this register in order to be valid.