4.3BSD - /usr/src/new/mkmf/src/defaultsfx.h

   1: ".c", SFXSRC, INCLUDE_C,    /* C */
   2: ".e", SFXSRC, INCLUDE_FORTRAN,  /* Efl */
   3: ".F", SFXSRC, INCLUDE_FORTRAN,  /* Fortran */
   4: ".f", SFXSRC, INCLUDE_FORTRAN,  /* Fortran */
   5: ".h", SFXHEAD, INCLUDE_NONE,    /* header */
   6: ".i", SFXHEAD, INCLUDE_NONE,    /* Pascal include */
   7: ".l", SFXSRC, INCLUDE_C,    /* Lex */
   8: ".o", SFXOBJ, INCLUDE_NONE, /* object */
   9: ".p", SFXSRC, INCLUDE_PASCAL,   /* Pascal */
  10: ".r", SFXSRC, INCLUDE_FORTRAN,  /* Ratfor */
  11: ".s", SFXSRC, INCLUDE_NONE, /* Assembler */
  12: ".y", SFXSRC, INCLUDE_C,    /* Yacc */

Usage of this include