VC++ 中的 #include

vc++中，#include有两种形式：
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The #include directive tells the preprocessor to treat the contents of a specified file as if those contents had appeared in the source program at the point where the directive appears.

引用

#include  "path-spec"
#include  <path-spec>

引用

Quoted form（引号）

总共四个地方
This form instructs the preprocessor to look for include files in the same directory of the file that contains the #include statement, and then in the directories of any files that include (#include) that file. The preprocessor then searches along the path specified by the /I compiler option, then along paths specified by the INCLUDE environment variable.

引用

Angle-bracket form（尖括号）

两个地方
This form instructs the preprocessor to search for include files first along the path specified by the /I compiler option, then, when compiling from the command line, along the path specified by the INCLUDE environment variable.

至于 the path specified by the /I compiler option，可以通过
配置属性-》c、c++-》命令行 中看到有哪些