How we could include header file that is not in the same folder as current file ?

[hhuyn.1]

I am studying "audio example" in "stm32f4cube mcu package".

In main.h file:

#include "stm32f411e_discovery.h"

How is this posible ?. "stm32f411e_discovery.h" file and "main.h" file are not in the same folder. 

[Piranha]

How is it possible that in the 21st century there are still so many illiterates, who can't even express themselves?

[hhuyn.1]

I'm feel so sorry.

In the "main.h" file, how we can include "stm32f411e_Discovery.h"

The file is in Drivers/BSP/STM32F411E-Discovery folder, not the same folder as "main.h". It is in example project folder.

In addition, why aren't header files in the same folder with source files ?