gfortran random_number query

[Matías Salvide]

Hello,
I'm Matías Salvide, I'm current working in game industry. I want to use the
RANDOM_NUMBER and RANDOM_SEED subroutines provided by gfortran 6.3.0 (for
Windows),  which implement the KISS algorithm. Where I could find the
sources codes of both? Actually, I already uses them in some of main
programs, but i don't have the subroutines fortran code (the compilar
recognized them automatically).
I installed gfortran from here: https://gcc.gnu.org/wiki/GFortranBinaries
The sources code of subroutines is somewhere in MinGw file?

Regards,
M. Salvide.