```    Program f08gtfe

!     F08GTF Example Program Text

!     Mark 27.0 Release. NAG Copyright 2019.

!     .. Use Statements ..
Use nag_library, Only: dznrm2, nag_wp, x04dbf, zhptrd, zsteqr, zupgtr
!     .. Implicit None Statement ..
Implicit None
!     .. Parameters ..
Integer, Parameter               :: nin = 5, nout = 6
!     .. Local Scalars ..
Complex (Kind=nag_wp)            :: scal
Integer                          :: i, ifail, info, j, k, ldq, n
Character (1)                    :: uplo
!     .. Local Arrays ..
Complex (Kind=nag_wp), Allocatable :: ap(:), q(:,:), tau(:), work(:)
Real (Kind=nag_wp), Allocatable  :: d(:), e(:), rwork(:)
Character (1)                    :: clabs(1), rlabs(1)
!     .. Intrinsic Procedures ..
Intrinsic                        :: abs, conjg, maxloc
!     .. Executable Statements ..
Write (nout,*) 'F08GTF Example Program Results'
!     Skip heading in data file
ldq = n
Allocate (ap(n*(n+1)/2),q(ldq,n),tau(n),work(n-1),d(n),e(n),rwork(2*n-2) &
)

!     Read A from data file

If (uplo=='U') Then
Else If (uplo=='L') Then
End If

!     Reduce A to tridiagonal form T = (Q**H)*A*Q
!     The NAG name equivalent of zhptrd is f08gsf
Call zhptrd(uplo,n,ap,d,e,tau,info)

!     Form Q explicitly, storing the result in Q
!     The NAG name equivalent of zupgtr is f08gtf
Call zupgtr(uplo,n,ap,tau,q,ldq,work,info)

!     Calculate all the eigenvalues and eigenvectors of A
!     The NAG name equivalent of zsteqr is f08jsf
Call zsteqr('V',n,d,e,q,ldq,rwork,info)

Write (nout,*)
If (info>0) Then
Write (nout,*) 'Failure to converge.'
Else

!       Print eigenvalues and eigenvectors

Write (nout,*) 'Eigenvalues'
Write (nout,99999) d(1:n)
Write (nout,*)
Flush (nout)

!       Normalize the eigenvectors, largest element real
Do i = 1, n
rwork(1:n) = abs(q(1:n,i))
k = maxloc(rwork(1:n),1)
scal = conjg(q(k,i))/abs(q(k,i))/dznrm2(n,q(1,i),1)
q(1:n,i) = q(1:n,i)*scal
End Do

!       ifail: behaviour on error exit
!              =0 for hard exit, =1 for quiet-soft, =-1 for noisy-soft
ifail = 0
Call x04dbf('General',' ',n,n,q,ldq,'Bracketed','F7.4','Eigenvectors', &
'Integer',rlabs,'Integer',clabs,80,0,ifail)

End If

99999 Format (8X,4(F7.4,11X,:))
End Program f08gtfe
```