Memory management fundamentals: In memory systems, what is the purpose of boundary (base and limit) registers maintained by the operating system/hardware?

Introduction / Context:
Protecting processes from one another is a core responsibility of an operating system. Base and limit (boundary) registers are a classic hardware support mechanism for relocation and protection in simple memory-management schemes.

Given Data / Assumptions:

• Boundary registers typically include a base (start physical address) and a limit (size or end address).
• They are checked on each memory reference.
• The goal is process isolation and prevention of illegal memory access.

Concept / Approach:

When a program accesses memory, the effective address = base + logical address. The hardware compares the logical address against the limit to ensure it is within the program’s assigned region. Thus, these registers effectively mark the beginning and ending boundaries of a program’s memory region.

Step-by-Step Solution:

Verification / Alternative check:

Intro OS texts show diagrams with base/limit protecting a contiguous segment per process; any reference outside the range triggers a trap.

Why Other Options Are Wrong:

• Temporary variable storage: handled in RAM/stack, not special registers.
• Only necessary with fixed partitions: also used with dynamic partitions and simple MMUs.
• Track page boundaries: paging uses page tables, not base/limit alone.

Common Pitfalls:

Confusing segmentation/paging with base-limit protection; assuming boundary registers store actual program data rather than address bounds.

Final Answer:

track the beginning and ending of programs