What is the role of the memory management unit in virtual memory?

• A. MMU translates virtual addresses using software routines only, without TLB.
• B. MMU handles memory allocation at compile time.
• C. MMU translates virtual addresses using page tables (and possibly TLB), enforces permissions and isolation.
• D. MMU manages file system metadata.

Answer: (C)

The essential role of the MMU in a virtual memory system is to translate virtual addresses to physical addresses and enforce protection between processes. It does this by using page tables to map virtual pages to physical frames, and it may rely on a translation lookaside buffer (TLB) to cache those translations for speed. When a virtual address is used, the MMU checks the relevant page table entry, pulls in the physical address, and also enforces access permissions (like read, write, execute) and user versus kernel mode, ensuring each process can’t access memory belonging to another. If the needed translation isn’t in the TLB, the hardware walks the page table in memory to obtain it; if the page isn’t present or access is not allowed, the MMU raises a fault for the OS to handle. It does not handle memory allocation at compile time or manage file system metadata, which are outside its responsibilities.