What is logical and physical address?

Logical Address: Address generated by CPU while a program is running is referred as Logical Address. The logical address is virtual as it does not exist physically. Hence, it is also called as Virtual Address. This address is used as a reference to access the physical memory location. The set of all logical addresses generated by a programs perspective is called Logical Address Space.

The logical address is mapped to its corresponding physical address by a hardware device called Memory-Management Unit. The address binding methods used by MMU generates identical logical and physical address during compile time and load time. However, while run-time the address binding methods generate different logical and physical address.

Physical Address: Physical Address identifies a physical location in a memory. MMU (Memory Management Unit) computes the physical address for the corresponding logical address. MMU also uses logical address computing physical address. The user never deals with the physical address. Instead, the physical address is accessed by its corresponding logical address by the user. The user program generates the logical address and thinks that the program is running in this logical address. But the program needs physical memory for its execution. Hence, the logical address must be mapped to the physical address before they are used. The logical address is mapped to the physical address using a hardware celled Memory-Management Unit. The set of all physical addresses corresponding to the logical addresses in a Logical address space is called Physical Address Space.