how to use subroutine written in FORTRAN90 to main program written in FORTRAN77
<p>My question is about FORTRAN 77 and FORTRAN 90. The main program (program.f77) is written in FORTRAN 77. One subroutine is written in FORTRAN 90. Say the name of the file is sub.f90 which has the subroutine. Now I want to use this subroutine to my main program. So I have used 'include sub.f90' to my main program but it did not work. My question is is there any way I can use sub.f90 to my main program (program.f77)? Any help will be appreciated. </p>