How to Calculate Physical Address from Logical Address
In computer systems, logical addresses and physical addresses are two essential concepts used to manage memory. Logical addresses are generated by the CPU and are used by programs to access memory. On the other hand, physical addresses are the actual locations in the memory where data is stored. The process of converting logical addresses to physical addresses is crucial for the proper functioning of the memory management unit (MMU). This article will discuss how to calculate physical address from logical address in a computer system.
Understanding Logical and Physical Addresses
Logical addresses are virtual addresses that are generated by the CPU. They are used by programs to access memory, and they do not necessarily correspond to the actual physical locations in the memory. Logical addresses are typically larger than physical addresses because they include additional information such as segment and offset values.
Physical addresses, on the other hand, are the actual locations in the memory where data is stored. They are used by the memory management unit to access the physical memory. Physical addresses are usually smaller than logical addresses since they only represent the actual location in the memory.
Mapping Logical to Physical Addresses
To calculate the physical address from a logical address, the computer system uses a technique called address translation. This process involves two main steps: segmentation and paging.
Segmentation
Segmentation is a memory management technique that divides the logical address space into smaller segments. Each segment represents a logical unit of memory, such as a program or a data structure. The logical address consists of a segment number and an offset within that segment.
To calculate the physical address, the system first looks up the segment number in the segment table. The segment table contains information about each segment, such as its base address and limit. Once the base address is obtained, the system adds the offset to it to get the physical address.
Paging
Paging is another memory management technique that divides the logical address space into fixed-size pages and the physical memory into fixed-size frames. The logical address consists of a page number and an offset within that page.
To calculate the physical address, the system first looks up the page number in the page table. The page table contains information about each page, such as its frame number. Once the frame number is obtained, the system adds the offset to it to get the physical address.
Summary
In summary, calculating the physical address from a logical address involves mapping the logical address to its corresponding physical location in the memory. This process can be achieved through segmentation and paging techniques. By using the segment or page table, the system can determine the base address or frame number and add the offset to it to obtain the physical address. Proper address translation is essential for the efficient and effective use of memory in a computer system.
