The maximum capacity of the virtual memory space is determined by the address structure, and the actual capacity is determined by the sum of internal and external memory.
Virtual storage space is a combination of hardware and software to expand user storage space. It uses internal memory and external memory (disk , CD), so that the two form an organic whole, supporting the running of large task programs that are much larger than the actual configured memory capacity. (Recommended learning:web front-end video tutorial)
Use memory and external storage in an organic combination to obtain a "memory" with a large capacity, which is virtual memory. If the process is not fully loaded, it is called virtual storage. It can be divided into two methods: fetching pages on demand and fetching segments on demand.
If the user does not consider the actual capacity of the memory when programming the program, that is, allowing the logical address space in the program to be larger than the absolute address space of the memory, then the user will feel great convenience.
Storage management uses the disk as the backup of the memory. When a large program is loaded into the memory, only the currently required part is loaded, and the rest is temporarily left on the disk. When information that is not in the memory is used during program execution, the operating system loads it into the memory.
If the memory space is insufficient, the operating system can use overwriting technology. In this way, users feel that the computer system provides a huge memory space.
In fact, this large-capacity memory space is not memory in the physical sense, but a storage management method in the operating system, which provides users with a virtual memory. Virtual memory has a larger capacity than actual memory and plays a role in expanding memory space.
Introduction of benefits
Can execute larger user programs in smaller available memory;
Can accommodate more program concurrency in memory Execution;
Does not have to affect the program structure during programming (compared with overwriting technology)
The virtual memory space available to users is usually larger than the physical memory
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