The Manchester Atlas paired paging hardware with a resident Supervisor that automated memory movement, scheduling and I/O, helping establish the operating system as an active manager of machine resources.
Multics treated computing as a shared utility and introduced a cluster of ideas—hierarchical files, segmented virtual memory, dynamic linking, access control and online reconfiguration—that shaped later operating systems.
Virtual memory let programs work in logical address spaces larger and more flexible than physical main memory, with hardware and operating systems moving pages between fast memory and backing storage.