Programs running in a computer need to be executed through memory. If the executed program occupies a large amount of memory, it will lead to memory exhaustion.
In the DOS era, there is no concept of virtual memory. If the system memory cannot provide the memory needed by the program, the program will not run normally.
In order to solve this problem, virtual memory technology is used in Windows, that is, a part of hard disk space is reserved for memory use. When the memory runs out, the computer will automatically call the hard disk as memory to relieve the memory tension.
But this can only make the program less prone to crash. When the system memory is insufficient and virtual memory is automatically called, the program will run slowly because the hard disk space is used as memory.