The main documentation of the Normal_Status Procedure contains additional explanation of this code listing.
function Normal_Status (S) result(Normal) ! Input variable. type(Status_type), intent(in) :: S ! Status to be checked. ! Output variable. type(logical) :: Normal ! Normal condition boolean. !~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ! Verify requirements. VERIFY(Valid_State(S),1) ! S is valid. ! Set normal boolean. Normal = status_flag(S%status)%severity == 'Normal' ! Verify guarantees. ! Normal should be what it was set to. VERIFY(Normal .eqv. (status_flag(S%status)%severity == 'Normal'),2) return end function Normal_Status