Procedures

Intent

In, Out, Inout

intent declares how an argument is used. in reads only, out writes only, inout both.

Program

Play the program to compute sum and difference through one subroutine.

intents.f90 
program intents_demo
    implicit none
    integer :: a, b, sum_, diff
    a = 10
    b = 3
    call summarize(a, b, sum_, diff)
    print '(I0, A, I0)', sum_, " ", diff
contains
    subroutine summarize(x, y, s, d)
        integer, intent(in) :: x, y
        integer, intent(out) :: s, d
        s = x + y
        d = x - y
    end subroutine summarize
end program intents_demo
intent(in) Read-only argument; the caller's value is unchanged.
intent(out) Output-only argument; the callee assigns it.
multiple outputs Use `intent(out)` arguments to return more than one value from a subroutine.