Memory management truths: Identify the statement that is not correct about common memory-management schemes (virtual memory, paging, segmentation).

Introduction / Context:
Operating systems use paging, segmentation, and virtual memory to manage limited physical RAM. Recognizing which statements are valid helps clarify performance trade-offs and design choices in OS memory subsystems.

Given Data / Assumptions:

• Virtual memory abstracts large address spaces; it is used widely.
• Paging splits memory into fixed-size pages/frames.
• Segmentation splits memory into variable-sized logical segments.

Concept / Approach:
Segmentation experiences external fragmentation because variable-sized segments leave gaps between allocations. Paging can have internal fragmentation because the last page of a process may be partially unused. Virtual memory is not limited to multi-user systems; it is common in single-user desktops and mobile devices. Systems can combine segmentation and paging (e.g., segmented virtual memory paged to frames).

Step-by-Step Solution:

Verification / Alternative check:
Consumer OSes (Windows, macOS, Linux) use virtual memory regardless of single vs. multi-user usage.

Why Other Options Are Wrong:
Options B, C, and D are standard textbook truths; marking them false contradicts established OS behavior.

Common Pitfalls:
Assuming “multi-user” implies the necessity for virtual memory; in reality, it addresses address-space abstraction and overcommit independent of user count.

Final Answer:
virtual memory is used only in multi-user systems