Logical vs Physical Address in OS: Key Differences Explained
A Logical Address is the identifier a program thinks it’s using—like apartment 3B—while the Physical Address is the actual spot on RAM hardware—like floor 4, unit 12.
Developers never see chips, only variables; users never see variables, only apps. That invisible layer tricks both groups into treating “where the OS says data is” and “where electrons really are” as the same thing, so the terms get swapped in meetings and docs.
Key Differences
Logical Address: generated by CPU, virtual, relocatable at runtime. Physical Address: fixed in silicon, tied to a memory module pin. The Memory Management Unit translates one to the other via page tables, invisible to software.
Which One Should You Choose?
Write code with Logical Addresses—let the OS juggle Physical ones. Only firmware or OS writers touch Physical Addresses when mapping DMA buffers or debugging hardware crashes.
Examples and Daily Life
When Chrome asks for 0x0040A000, it’s a Logical Address; the DRAM chip might receive 0x7A3F8000. Same Netflix frame, two different labels—one for the app, one for the electrons.
Can two programs share one Physical Address?
Yes, through Logical Address mapping, the OS lets many apps appear to own unique memory while pointing to the same RAM page.
Does more RAM change Logical Address size?
No, Logical Address space is set by CPU architecture (e.g., 64-bit), not by how many sticks you plug in.