Swapping is a mechanism in which a process can be swapped temporarily out of main memory (or move) to secondary storage (disk) and make that memory available to other processes.
A process is basically a program in execution. The execution of a process must progress in a sequential fashion.
The act of determining which process is in the ready state, and should be moved to the running state is known as Process Scheduling.
Memory allocation is a process by which computer programs and services are assigned with physical or virtual memory space.
Single allocation is the simplest memory management technique. All the computer's memory, usually with the exception of a small portion reserved for the operating system, is available to the single application.
In this type of allocation, main memory is divided into a number of fixed-sized partitions where each partition should contain only one process. When a partition is free, a process is selected from the input queue and is loaded into the free partition. When the process terminates, the partition becomes available for another process.
-First-fit: In the first fit, partition is allocated which is first sufficient from the top of Main Memory.
-Best-fit: Allocate the process to the partition which is first smallest sufficient partition among the free available partition.
-Worst-fit: Allocate the process to the partition which is largest sufficient among the freely available partitions available in the main memory.
In virtual memory systems, demand paging is a type of swapping in which pages of data are not copied from disk to RAM until they are needed. In contrast, some virtual memory systems use anticipatory paging, in which the operating system attempts to anticipate which data will be needed next and copies it to RAM before it is actually required
A page table is the data structure used by a virtual memory system in a computer operating system to store the mapping between virtual addresses and physical addresses.
A page fault is a type of exception raised by computer hardware when a running program accesses a memory page that is not currently mapped by the memory management unit (MMU) into the virtual address space of a process.