NAG Library Manual, Mark 28.5
```    Program f07bsfe

!     F07BSF Example Program Text

!     Mark 28.5 Release. NAG Copyright 2022.

!     .. Use Statements ..
Use nag_library, Only: nag_wp, x04dbf, zgbtrf, zgbtrs
!     .. Implicit None Statement ..
Implicit None
!     .. Parameters ..
Integer, Parameter               :: nin = 5, nout = 6
Character (1), Parameter         :: trans = 'N'
!     .. Local Scalars ..
Integer                          :: i, ifail, info, j, k, kl, ku, ldab,  &
ldb, n, nrhs
!     .. Local Arrays ..
Complex (Kind=nag_wp), Allocatable :: ab(:,:), b(:,:)
Integer, Allocatable             :: ipiv(:)
Character (1)                    :: clabs(1), rlabs(1)
!     .. Intrinsic Procedures ..
Intrinsic                        :: max, min
!     .. Executable Statements ..
Write (nout,*) 'F07BSF Example Program Results'
!     Skip heading in data file
Read (nin,*) n, nrhs, kl, ku
ldab = 2*kl + ku + 1
ldb = n
Allocate (ab(ldab,n),b(ldb,nrhs),ipiv(n))

!     Read A and B from data file

k = kl + ku + 1

!     Factorize A

!     The NAG name equivalent of zgbtrf is f07brf
Call zgbtrf(n,n,kl,ku,ab,ldab,ipiv,info)

Write (nout,*)
Flush (nout)
If (info==0) Then

!       Compute solution
!       The NAG name equivalent of zgbtrs is f07bsf
Call zgbtrs(trans,n,kl,ku,nrhs,ab,ldab,ipiv,b,ldb,info)

!       Print solution

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

Else
Write (nout,*) 'The factor U is singular'
End If

End Program f07bsfe
```