![]() ![]() As a result, the VMM will generate a 490 MB file on the hard disc to contain the extra RAM that is necessary. The operating system will then allocate 490 MB of virtual memory and manage it with an application called the Virtual Memory Manager (VMM). However, there is now only 10 MB of actual capacity accessible on the RAM. Let's understand the working of virtual memory using the example shown below.Īssume that an operating system uses 500 MB of RAM to hold all of the running processes. That's how virtual memory made its place in our daily lives. ![]() However, it was not until 1985, that Intel introduced virtual memory, which marked the beginning of virtual memory in personal computers. By the late 1970s, the idea of virtual memory was properly developed and imbibed into commercial computers. It was the criticism that the concept of virtual memory of that time faced that led to building the virtual memory that exists now. The first virtual memory was developed in 1959. However, since access to this was slow, they thought that it would be good to have some kind of fast cheap memory that would help in solving this problem. When this happened, they were forced to use the hard drive's memory. When programs grew and required more memory than there was present, the system ran out of memory. Back in those times, storage was highly expensive, and thus expanding it would cause trouble. History of Virtual Memory in OSĮarly computers had two types of storage namely primary and secondary. This can be done by exchanging data between RAM and virtual memory based on its need. This frees up RAM space, which may then be utilized to store data that the system will need to access.Ī system can continue to run smoothly with significantly less physical RAM than it would normally require. To mitigate this issue, some data stored in RAM that isn't being actively used can be temporarily relocated to virtual memory. When running multiple heavy applications at once, the system's RAM may get overloaded. In particular, the system can behave as if its total RAM resources were equal to the whole amount of physical RAM plus the complete amount of virtual RAM. Virtual memory allows a system to execute heavier applications or multiple applications simultaneously without exhausting the RAM (Random Access Memory). Virtual memory is a part of the system's secondary memory that acts and gives us a feel as if it is a part of the main memory. Such a mapping mechanism is called a page table. To make it easy to search, you may keep a note of where you have placed what clothing items. The clothes at the back can also be accessed when needed although they may take a little more time. Now, in the above scenario, consider yourself to be the operating system and the backside of your wardrobe to be the hard disk. You keep the clothes that you would like to wear in front so that they are handy. Imagine the physical memory of your computer in the front section of your wardrobe. The article does not compare virtual memory with other forms of memory, nor does it speak about paging and segmentation in detail.We will also cover the pros and cons of virtual memory in detail. ![]() We will also learn about concepts of demand paging, page frames, page tables, and swapping.This article defines virtual memory and covers the history and workings of virtual memory in OS.It is commonly implemented using demand paging. It helps in running multiple applications with low main memory and increases the degree of multiprogramming in systems. It is a part of the secondary storage that gives the user the illusion that it is a part of the main memory. Virtual memory is a mechanism used to manage memory using hardware and software.
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