Unsigned numbers have a trailing @code{u} as suffix, optionally followed
by a @code{KIND} number separated by an underscore.
-Input and output can be done using the @code{I} and (to be
-implemented) @code{X}, @code{O} and @code{Z} descriptors, plus
-unformatted I/O.
+Input and output can be done using the @code{I}, @code{B}, @code{O}
+and @code{Z} descriptors, plus unformatted I/O.
Here is a small, somewhat contrived example of their use:
@smallexample
--- /dev/null
+! { dg-do run }
+! { dg-options "-funsigned" }
+! Test I/O with Z, O and B descriptors.
+
+program main
+ implicit none
+ unsigned(kind=8) :: u,v
+ integer :: i
+ open(10,status="scratch")
+ u = 3u
+ do i=0,63
+ write (10,'(Z16)') u
+ u = u + u
+ end do
+ rewind 10
+ u = 3u
+ do i=0,63
+ read (10,'(Z16)') v
+ if (u /= v) then
+ print *,u,v
+ end if
+ u = u + u
+ end do
+ rewind 10
+ u = 3u
+ do i=0,63
+ write (10,'(O22)') u
+ u = u + u
+ end do
+ rewind 10
+ u = 3u
+ do i=0,63
+ read (10,'(O22)') v
+ if (u /= v) then
+ print *,u,v
+ end if
+ u = u + u
+ end do
+
+ rewind 10
+ u = 3u
+ do i=0,63
+ write (10,'(B64)') u
+ u = u + u
+ end do
+ rewind 10
+ u = 3u
+ do i=0,63
+ read (10,'(B64)') v
+ if (u /= v) then
+ print *,u,v
+ end if
+ u = u + u
+ end do
+
+end program main