Difference between .h and .hpp [duplicate]

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• *.h or *.hpp for your class definitions 16 answers

Most of the modern C++ code that I see these days, seem to use .hpp for the header files instead of .h extension. Also the current trend seems to be to declare and define the functions in the .hpp file itself instead of a separate .cpp file and then call the classes so defined in .cpp files. My question is how is .hpp really different from .h and why this trend of defining everything in a .hpp file.