2358	 The Multics Virtual Memory Concepts and Design	 As experience with use of on-line operating systems has grown the need to share information among system users has become increasingly apparent. Many contemporary systems permit some degree of sharing. Usually sharing is accomplished by allowing several users to share data via input and output of information stored in files kept in secondary storage. Through the use of segmentation however Multics provides direct hardware addressing by user and system programs of all information independent of its physical storage location. Information is stored in segments each of which is potentially sharable and carries its own independent attributes of size and access privilege. Here the design and implementation considerations of segmentation and sharing in Multics are first discussed under the assumption that all information resides in large segmented main memory. Since the size of main memory on contemporary systems is rather limited it is then shown how the Multics software achieves the effect of a large segmented main memory through the use of the Honeywell segmentation and paging hardware. operating system Multics virtual memory segmentation information sharing paging memory management memory hierarchy
