Difference between EXTERNAL and INTERFACE

To NG:

I am quite confuse when to use EXTERNAL and INTERFACE when it comes to
calling a F77 function/subroutine. Let's say there's a F77 function called
F77_function in  F77_SUB.F,  and I want to call the function from a program
written in F90. Do I use EXTERNAL or INTERFACE to describe the F77 function?


Thanks.

"Jason" <JC20032344@hotmail.com> wrote in message
news:Voxcd.5979$232.3762@trnddc09...
> To NG:
>
>     I am quite confuse when to use EXTERNAL and INTERFACE when it comes to
> calling a F77 function/subroutine. Let's say there's a F77 function called
> F77_function in  F77_SUB.F,  and I want to call the function from a
program
> written in F90. Do I use EXTERNAL or INTERFACE to describe the F77
function?
>
Either, but not both. An interface block is better as it permits all sorts
of checks to be made, but external suffices (see also "Fortran 90/95
Explained", Section 5.11).

Hope that helps,

Mike Metcalf