Memory Management — Segmentation

Abstract

The memory management system described in chapter 8 provides an adequate set of facilities for implementing a reasonable time-sharing system. Each user process has its own virtual store which is protected from interference by other processes by the use of the base-limit register. Additionally, this mechanism protects the operating system from illegal accesses by the user programs. Many early computers relied solely on this technique for implementing a suitable multi-access system, but there are still a number of major problems outstanding for the system designer, most notably: (a) fragmentation, (b) locality of programs and (c) sharing of data structures or code, such as compilers and editors. Each of these will now be considered.