Logical and Physical Address in Operating System (original) (raw)

Last Updated : 15 Apr, 2026

Memory access in operating systems happens through two types of addresses: logical (virtual) and physical. The Memory Management Unit (MMU) sits between the CPU and the physical memory. Its job is to translate every logical address into the correct physical address.

• Programs to believe they have a large, continuous memory space
• The OS protects one process’s memory from another process
• Efficient use of RAM through paging, segmentation, or both

Whenever the CPU accesses memory, it sends a logical address → the MMU converts it → the corresponding physical address in RAM is accessed.

Logical Address

A logical address is generated by the CPU while a program runs. It represents the address from the process’s perspective and does not exist physically, hence it is also called a virtual address.

• The logical address space is the set of all logical addresses a process can generate.
• Programs use logical addresses to reference memory, and the MMU translates them into physical addresses when accessing actual memory.

Physical Address

A physical address is the real location in main memory (RAM) where data or instructions are stored. The physical address space consists of all physical addresses corresponding to logical addresses.

• The MMU performs address translation using a page table, mapping each logical page to a physical frame.
• This allows processes to access memory transparently, without knowing actual memory locations.

**Similarities in Logical and Physical Addresses

• Both logical and physical addresses are used to identify a specific location in memory.
• Each address type can be represented in different formats such as binary, hexadecimal, or decimal.
• They have a finite range, which is determined by the number of bits used to represent them.

Memory Management

Memory Management Unit

The Memory Management Unit (MMU) is a hardware component in the computer system that handles all memory and caching operations associated with the CPU. Its main function is to translate **logical (virtual) addresses generated by the CPU into physical addresses in main memory.

Key functions of Memory Management Unit

• Logical addresses provide abstraction, so processes don’t need to know physical locations.
• These logical addresses are translated into physical addresses using a page table.
• Translation is transparent and handled by hardware (MMU).
• Enables efficient memory management through paging and segmentation.

Logical Address vs. Physical Address