It is a memory managermnet concept where the operating system copies the dats from the disk space to the main memory (RAM) only when is trying to access the page. it is like we have to attempt the page again, when the page fault has occured while trying to get the data.
Thrashing
thrashing
Any operating system that allows for "paging" or "swapping" is capable of this.
Paging has many advantages. First of all, paging allows you to relocate memory areas to other places where they are more useful. For example, any operating system must divide memory in two areas, one for the operating system itself (OS, data, management tables, ...) and one for the user programs. The area for the OS must be subdivided into areas to store each driver and its data. The area for the user must be subdivided to store each program and its data.
Some Operating Systems periodically look for pages that have not been recently referenced and add them to the Free page queue, after paging them out if they have been modified.
Demand paging is a process which involves the copying and relocation of data from a secondary storage system to random access memory (RAM), a main memory storage system. Demand paging copies and relocates data to facilitate the fastest access to that data. Once the data is relocated, demand paging sends a command to the operating system to inform it that the data file or files are now ready to be loaded. Demand paging is performed on demand, or after a command has been sent to retrieve specific data.
In computer operating systems, demand paging is an application of virtual memory. In a system that uses demand paging, the operating system copies a disk page into physical memory only if an attempt is made to access it (i.e., if a page fault occurs). It follows that a process begins execution with none of its pages in physical memory, and many page faults will occur until most of a process's working set of pages is located in physical memory. This is an example of lazy loading techniques.
Thrashing
thrashing
In demand paging, a page is not loaded into main memory until it is needed. In pure demand paging, even a single page is not loaded into memory initially. Hence pure demand paging causes a page fault. Page fault, the situation in which the page is not available whenever a processor needs to execute it.
The question is not very clear - in general the implementation of paging is too complex to answer in a Wiki answer entry; I suggest you take a look at any Operating System theory book.
Any operating system that allows for "paging" or "swapping" is capable of this.
"Paging" is when the operating system writes contents of RAM memory to disk, to free space for other uses.A paging algorithm specifies which RAM content to page (write to disk) when it needs more space.See related link.
Paging has many advantages. First of all, paging allows you to relocate memory areas to other places where they are more useful. For example, any operating system must divide memory in two areas, one for the operating system itself (OS, data, management tables, ...) and one for the user programs. The area for the OS must be subdivided into areas to store each driver and its data. The area for the user must be subdivided to store each program and its data.
The best paging system is Wendy's drive thru
Some Operating Systems periodically look for pages that have not been recently referenced and add them to the Free page queue, after paging them out if they have been modified.
In case of simple paging all pages should be in main memory to run a process..while in case of virtual memory paging pages can be loaded as needed by the processor i.e. called demand paging...