How DLLs are shared among applications?

I am under the 开发者_StackOverflow社区impression that DLLs are mapped into the address space of the calling process. If that is the case, how DLLs can be shared among other processes?

Regards, Arun

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There are two ways:

1) Common library code is put in DLL files (it stands for Dynamic-Link Library), so that common portions of code uses less space on HDD (and are easier to update).

2) In-memory sharing (copy-on-write scheme, when pages that are common to several processes are mapped to the same physical page).