Process Address Space in operating systems

By: Prof. Fazal Rehman Shamil
Last modified on August 7th, 2020

What is Process Address Space?

Address space is a space in computer memory. And process Address Space means a space that is allocated in memory for a process. Every process has an address space

Address Space can be of two types

  1. Physical Address Space
  2. Virtual Address Space

physical and logical address space in OS

Physical address space

he physical address is the actual location in the memory that exist physically. System access the data in the main memory, with the help of physical address. Every thing in the computer has a unique physical address. We needs to mapped it to make the address accessible. MMU is responsible for mapping.

Virtual Address Space

Virtual Address Space is an address space that is created outside the main memory inside the virtual memory, and it is created in the hard disk.

When our main memory is less and we want to get more benefit from this less memory, then we create virtual memory.

Logical Address is the address is always generated by CPU while running a program. The logical address is also called virtual address. Virtual address does not exist physically, so we can say that physical address is the logical address.
How to access the physical memory location by CPU?
Logical Address is used as a reference to access the physical memory location by CPU. The Memory-Management Unit uses the address-binding methods for mapping the logical address to its corresponding physical address.

Basic ADDRESS generated by CPU is called LOGICAL ADDRESS. PHYSICAL ADDRESS  is the actual location in a memory unit.
Generation generated by the CPU Computed by MMU
Access logical address can be used to access the physical address by the user. The user can’t directly access physical address but it is possible indirectly.
Visibility logical address of a program is visible to the user. physical address of program is not visible to the user.
Address Space set of all logical addresses generated by CPU are called logical addresses. Addresses mapped to the corresponding logical addresses.

virtual memory

Virtual memory is memory outside the main memory and inside the hard disk

Virtual memory acts as the main memory but it is actually not the main memory

When a process is loads in OS, its address space is created.

Prof. Fazal Rehman Shamil
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