NAG Library Manual, Mark 28.6
```    Program f07hnfe

!     F07HNF Example Program Text

!     Mark 28.6 Release. NAG Copyright 2022.

!     .. Use Statements ..
Use nag_library, Only: nag_wp, x04dff, zpbsv
!     .. Implicit None Statement ..
Implicit None
!     .. Parameters ..
Integer, Parameter               :: nin = 5, nout = 6
Character (1), Parameter         :: uplo = 'U'
!     .. Local Scalars ..
Integer                          :: i, ifail, info, j, kd, ldab, n
!     .. Local Arrays ..
Complex (Kind=nag_wp), Allocatable :: ab(:,:), b(:)
Character (1)                    :: clabs(1), rlabs(1)
!     .. Intrinsic Procedures ..
Intrinsic                        :: max, min
!     .. Executable Statements ..
Write (nout,*) 'F07HNF Example Program Results'
Write (nout,*)
!     Skip heading in data file
ldab = kd + 1
Allocate (ab(ldab,n),b(n))

!     Read the upper or lower triangular part of the band matrix A
!     from data file

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

!     Read b from data file

!     Solve the equations Ax = b for x
!     The NAG name equivalent of zpbsv is f07hnf
Call zpbsv(uplo,n,kd,1,ab,ldab,b,n,info)

If (info==0) Then

!       Print solution

Write (nout,*) 'Solution'
Write (nout,99999) b(1:n)

!       Print details of factorization

Write (nout,*)
Flush (nout)

!       ifail: behaviour on error exit
!              =0 for hard exit, =1 for quiet-soft, =-1 for noisy-soft
ifail = 0
If (uplo=='U') Then
Call x04dff(n,n,0,kd,ab,ldab,'Bracketed','F7.4','Cholesky factor U', &
'Integer',rlabs,'Integer',clabs,80,0,ifail)
Else If (uplo=='L') Then
Call x04dff(n,n,kd,0,ab,ldab,'Bracketed','F7.4','Cholesky factor L', &
'Integer',rlabs,'Integer',clabs,80,0,ifail)
End If

Else
Write (nout,99998) 'The leading minor of order ', info,                &
' is not positive definite'
End If

99999 Format ((3X,4(' (',F7.4,',',F7.4,')',:)))
99998 Format (1X,A,I3,A)
End Program f07hnfe
```