Virtual address space

1. Concept

Every process Will allocate virtual address space , stay 32 On the bit machine , The address space is 4G . It is usually stored in virtual form , When an application uses a virtual address to access memory /a.out perform ,mmu Convert the virtual address to the physical address to execute （ Normal files are stored on disk ）

Segment error ： Illegal memory access , Kernel space is protected
The heap space must be released after storage

The pointer variable in the process , What is saved is the virtual address . When an application uses a virtual address to access memory , processor （CPU） Will convert it to a physical address （MMU）.

MMU： Convert virtual addresses to physical addresses .

The advantage of doing so is ：
Process isolation , Better protect the safe operation of the system
Shielding the troubles caused by physical differences , It is convenient for the operating system and compiler to arrange the process address

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