In this example, the SIZE intrinsic is used to set the extent of the work array based on the size of the input arrays. The work array is an automatic array; the inputs are assumed-shape arrays. With Fortran 90 constructs, there is therefore no need to supply explicit size information anywhere within this subroutine. Even the potential need to specify explicit bounds for DO-loops has been eliminated, through the use of Fortran 90 array assignments.

 SUBROUTINE swap(a,b)
 IMPLICIT NONE
 REAL, DIMENSION(:) :: a,b
 REAL, DIMENSION(SIZE(a)) :: work
 work = a 
 a = b
 b = work
 END

This example illustrates an important principle of Fortran 90: arrays should be thought of as ``array objects'' which contain embedded information about size and other attributes of the array, as well as the array data.