Difference between logical address space and physical address space?

Logical address space refers to the range of addresses that a process can use to access memory, as seen by the process itself. It is typically larger than the physical address space and is managed by the operating system. The logical address space is divided into fixed-size blocks called pages or segments.

Physical address space, on the other hand, refers to the actual physical memory locations where data is stored. It is the range of addresses that the memory hardware can access directly. The physical address space is limited by the amount of physical memory available in the system.

In summary, the logical address space is the range of addresses that a process can use, while the physical address space is the actual physical memory locations where data is stored. The operating system maps logical addresses to physical addresses to manage memory efficiently.

Logical Address Space

- A virtual address space used by a program or process.
- It is a contiguous range of memory addresses that the program can reference.
- Not directly mapped to physical memory and can be larger than the physical address space.
- Managed by the operating system's memory management unit (MMU).

Physical Address Space

- The actual physical memory of the computer.
- A contiguous range of memory addresses that the hardware can directly access.
- Limited by the physical memory capacity of the system.
- Assigned by the MMU using a mapping mechanism.

Key Differences

| Feature | Logical Address Space | Physical Address Space |
|---|---|---|
| Accessibility | Used by programs, not directly accessible by hardware | Directly accessed by hardware |
| Size | Can be larger than physical address space | Limited by physical memory size |
| Management | Managed by MMU | Managed by MMU |
| Mapping | Addresses mapped to physical addresses by MMU | Physical addresses directly available to hardware |
| Purpose | Allows programs to use virtual memory | Provides direct access to physical memory |
| Protection | Provides isolation and protection between processes | No protection mechanism |

Example

- A program may have a logical address space of 4GB, but the physical address space of the computer is only 2GB.
- When the program references a logical address, the MMU translates it to a physical address within the 2GB physical address space.