Routines can now be called with keyword arguments and can use default arguments, that means that some arguments can be given with keywords instead of position and some do not have to be given at all, in which case a standard or default value is used. ... IMPLICIT NONE INTERFACE SUBROUTINE SOLVE (A, B, N) INTEGER, INTENT (IN) : : N REAL, INTENT(OUT) : : A REAL, INTENT(IN), OPTIONAL : : B END SUBROUTINE SOLVE END INTERFACE REAL X ! ... You will use keyword arguments and default arguments so that . ...

... Compact Binaries . ... Unlike the Sun, most stars in our Galaxy orbit another star: these systems are called binary stars. Generally it takes many years for the two stars to orbit around each other. ... These binaries are interesting for many reasons. One is that they are predicted to emit lots of gravitational waves. ... Over time as gravitational waves are emitted, the time taken for the two stars to orbit one another changes by a small but measurable amount. ...