Angle Brackets vs. Double Quotes in C Header Inclusion: When Should I Use Which?

Header File Inclusion in C : Angle Brackets vs. Double Quotes

When including header files in C , the choice between angle brackets (<) and double quotes (") requires consideration. Each notation emphasizes different search paths and file types during the inclusion process.

Angle brackets (<) are typically used to include system-level header files. These header files come preinstalled with your development environment and are located in predefined system directories. By including a header file using angle brackets, you instruct the compiler to search for it within these system directories. For instance, #include would search for the QPushButton header file in the system-level headers.

On the other hand, double quotes (") prioritize headers located in your current working directory over system headers. This means that #include "MyFile.h" would first search for the MyFile.h header in the directory where your code file resides. If it's not found there, the compiler will then continue to search the system paths.

Understanding this distinction is crucial because system headers generally contain declarations for essential libraries and functionalities, while user-defined headers are specific to your project. By using angle brackets for system headers and double quotes for custom headers, you can control the search order and prevent conflicts between files.

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