Header file and source file in C++

Header files

The compiler doesn't compile header files since these are meant to be included into source files.

Even though one can put declarations and definitions for a class in the same file, there are good reasons to separate them, and sometimes there are also good reasons to put them together.

Member functions are implicitly inline they are defined side their class.

Why separating them

• The definition may change more often than the definition. If you put them together and this file is included in anther source file, any change to the definition will cause the other dependent files to be recompiled again.