```    Program f08usfe

!     F08USF Example Program Text

!     Mark 27.0 Release. NAG Copyright 2019.

!     .. Use Statements ..
Use nag_library, Only: dsterf, nag_wp, zhbgst, zhbtrd, zpbstf
!     .. Implicit None Statement ..
Implicit None
!     .. Parameters ..
Integer, Parameter               :: nin = 5, nout = 6
!     .. Local Scalars ..
Integer                          :: i, info, j, ka, kb, ldab, ldbb, ldx, &
n
Character (1)                    :: uplo
!     .. Local Arrays ..
Complex (Kind=nag_wp), Allocatable :: ab(:,:), bb(:,:), work(:), x(:,:)
Real (Kind=nag_wp), Allocatable  :: d(:), e(:), rwork(:)
!     .. Intrinsic Procedures ..
Intrinsic                        :: max, min
!     .. Executable Statements ..
Write (nout,*) 'F08USF Example Program Results'
!     Skip heading in data file
ldab = ka + 1
ldbb = kb + 1
ldx = n
Allocate (ab(ldab,n),bb(ldbb,n),work(n),x(ldx,n),d(n),e(n-1),rwork(n))

!     Read A and B from data file

If (uplo=='U') Then
Do i = 1, n
End Do
Do i = 1, n
End Do
Else If (uplo=='L') Then
Do i = 1, n
End Do
Do i = 1, n
End Do
End If

!     Compute the split Cholesky factorization of B
!     The NAG name equivalent of zpbstf is f08utf
Call zpbstf(uplo,n,kb,bb,ldbb,info)

Write (nout,*)
If (info>0) Then
Write (nout,*) 'B is not positive definite.'
Else

!       Reduce the problem to standard form C*y = lambda*y, storing
!       the result in A
!       The NAG name equivalent of zhbgst is f08usf
Call zhbgst('N',uplo,n,ka,kb,ab,ldab,bb,ldbb,x,ldx,work,rwork,info)

!       Reduce C to tridiagonal form T = (Q**H)*C*Q
!       The NAG name equivalent of zhbtrd is f08hsf
Call zhbtrd('N',uplo,n,ka,ab,ldab,d,e,x,ldx,work,info)

!       Calculate the eigenvalues of T (same as C)
!       The NAG name equivalent of dsterf is f08jff
Call dsterf(n,d,e,info)

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

!         Print eigenvalues

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

99999 Format (3X,(8F8.4))
End Program f08usfe
```