[C ++] The difference between double quotes and book titles in C ++ header files

The difference between the use of "" and <> in C ++ header files:

• Use "" to search all directories.
• Use <> to search the current directory.

Under normal circumstances, self-defined header files should use "", because these files are placed in the project directory (that is, the source program directory), rather than placed in the public header file directory, if you use <> you can not find the header file .

The header files provided by the system, such as math.h, can use <>.