<P> Some systems allow partitions to be swapped out to secondary storage to free additional memory . Early versions of IBM's Time Sharing Option (TSO) swapped users in and out of a single time - sharing partition . </P> <P> Paged allocation divides the computer's primary memory into fixed - size units called page frames, and the program's virtual address space into pages of the same size . The hardware memory management unit maps pages to frames . The physical memory can be allocated on a page basis while the address space appears contiguous . </P> <P> Usually, with paged memory management, each job runs in its own address space . However, there are some single address space operating systems that run all processes within a single address space, such as IBM i, which runs all processes within a large address space, and IBM OS / VS2 SVS, which ran all jobs in a single 16MiB virtual address space . </P> <P> Paged memory can be demand - paged when the system can move pages as required between primary and secondary memory . </P>

A static partitioned memory management system has a total of six partitions