02 Physical and logical address spaces

Difference Between Physical and Logical Address Space

Physical Address Space

• Definition: Refers to the actual addresses in the computer’s hardware (RAM).
• Characteristics:
  • Represents the physical memory layout.
  • Determined by the installed RAM.
  • Managed by the OS and hardware (e.g., memory management unit).

Logical Address Space

• Definition: Refers to the addresses generated by the CPU during program execution.
• Characteristics:
  • Represents an abstraction for a program’s memory.
  • Allows each process to have its own address space, ensuring isolation.
  • Requires translation to physical addresses, often through mechanisms like page tables.

1. Physical Address Space is concerned with actual memory locations in the hardware
2. Logical Address Space pertains to addresses generated by programs that require translation into physical addresses.

Aspect	Physical Address Space	Logical Address Space
Definition	Refers to the actual memory addresses in the computer’s hardware (RAM).	Refers to the addresses generated by the CPU during program execution.
Address Range	Determined by the amount of physical memory installed in the system.	Determined by the program’s requirements and the maximum addressable space by the architecture (e.g., 32-bit, 64-bit).
Visibility	Visible to the memory management unit (MMU) and the OS.	Visible to the process and the compiler; not directly accessible to the hardware.
Representation	Actual locations in RAM, defined by physical addresses (e.g., 0x0000, 0x0001).	Abstract locations used by a program, defined by logical addresses (e.g., virtual addresses).
Translation	No translation is needed; it refers directly to RAM.	Requires translation to physical addresses through mechanisms like page tables.
Isolation	Physical addresses can be shared among processes.	Each process has its own logical address space, ensuring isolation and security.
Management	Managed by the OS and hardware.	Managed by the OS through the MMU and page tables.