对于不支持低级访问的语言，如何实现 I/O 库例程？
不支持对机器进行低级访问的语言（例如内存映射 I/O）通常（如果不是总是）具有提供此类访问的库例程。现在，如果语言本身不支持这种访问，那么这些库例程是如何实现的呢？
Languages which don't support low level access to the machine, such as memory-mapped I/Os, often (if not always) have library routines which provides such access. Now, if the language itself does not support such access, how are these library routines implemented?
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这实际上取决于语言。某些语言具有“互操作”功能，允许用该语言编写的方法调用可以用另一种语言（C、汇编语言等）实现的库原语。
例如，.NET 语言具有 P/Invoke 工具，允许它们调用非托管 DLL（可以用 C、C++、汇编语言或任何其他允许从 DLL 导出函数的语言编写），但对于内部 CLR 使用，也有“内部调用”修饰符，它是对在 CLR DLL 之一内实现的库原语的直接调用。
It really depends on the language. Some languages have an "interop" facility which allows a method written in that language to call a library primitive that can be implemented in another language (C, assembler, etc.).
For example, .NET languages have the P/Invoke facility that allows them to call unmanaged DLLs (that can be written in C, C++, assembler, or any other language that allows exported functions from DLLs), but for internal CLR use there's also the "internal call" modifier which is a direct call into a library primitive implemented inside one of the CLR DLLs.