Define virtual memory, paging, memory management and swapping in operating system - Tech-n-Savvy Blogger

Virtual Memory:

Virtual memory is a memory management capability of an OS that uses hardware and software to allow a computer to compensate for physical memory shortages by temporarily transferring data from random access memory (RAM) to disk storage. Virtual address space is increased using active memory in RAM and inactive memory in hard disk drives (HDDs) to form contiguous addresses that hold both the application and its data.

Paging:

Paging is a memory management scheme that eliminates the need for contiguous allocation of physical memory. This scheme permits the physical address space of a process to be non – contiguous.

• Logical Address or Virtual Address (represented in bits): An address generated by the CPU
• Logical Address Space or Virtual Address Space( represented in words or bytes): The set of all logical addresses generated by a program
•  Physical Address (represented in bits): An address actually available on memory unit
• Physical Address Space (represented in words or bytes): The set of all physical addresses corresponding to the logical addresses

What is Memory Management? Also Define Swapping.

Memory Management:

Main Memory refers to a physical memory that is the internal memory to the computer. The word main is used to distinguish it from external mass storage devices such as disk drives. Main memory is also known as RAM. The computer is able to change only data that is in main memory. Therefore, every program we execute and every file we access must be copied from a storage device into main memory.

All the programs are loaded in the main memory for execution. Sometimes complete program is loaded into the memory, but sometimes a certain part or routine of the program is loaded into the main memory only when it is called by the program, this mechanism is called Dynamic Loading, this enhance the performance.

Also, at times one program is dependent on some other program. In such a case, rather than loading all the dependent programs, CPU links the dependent programs to the main executing program when it’s required. This mechanism is known as Dynamic Linking.

Swapping:

A process needs to be in memory for execution. But sometimes there is not enough main memory to hold all the currently active processes in a time sharing system. So, excess process are kept on disk and brought in to run dynamically. Swapping is the process of bringing in each process in main memory, running it for a while and then putting it back to the disk.