NAG Library Manual, Mark 28.7
```    Program f04ccfe

!     F04CCF Example Program Text

!     Mark 28.7 Release. NAG Copyright 2022.

!     .. Use Statements ..
Use nag_library, Only: f04ccf, nag_wp, x04dbf
!     .. Implicit None Statement ..
Implicit None
!     .. Parameters ..
Integer, Parameter               :: nin = 5, nout = 6
!     .. Local Scalars ..
Real (Kind=nag_wp)               :: errbnd, rcond
Integer                          :: i, ierr, ifail, ldb, n, nrhs
!     .. Local Arrays ..
Complex (Kind=nag_wp), Allocatable :: b(:,:), d(:), dl(:), du(:), du2(:)
Integer, Allocatable             :: ipiv(:)
Character (1)                    :: clabs(1), rlabs(1)
!     .. Executable Statements ..
Write (nout,*) 'F04CCF Example Program Results'
Write (nout,*)
Flush (nout)
!     Skip heading in data file
ldb = n
Allocate (b(ldb,nrhs),d(n),dl(n-1),du(n-1),du2(n-2),ipiv(n))
!     Read A and B from data file

!     Solve the equations AX = B for X

!     ifail: behaviour on error exit
!            =0 for hard exit, =1 for quiet-soft, =-1 for noisy-soft
ifail = 1
Call f04ccf(n,nrhs,dl,d,du,du2,ipiv,b,ldb,rcond,errbnd,ifail)

If (ifail==0) Then
!       Print solution, estimate of condition number and approximate
!       error bound

ierr = 0
Call x04dbf('General',' ',n,nrhs,b,ldb,'Bracketed',' ','Solution',     &
'Integer',rlabs,'Integer',clabs,80,0,ierr)

Write (nout,*)
Write (nout,*) 'Estimate of condition number'
Write (nout,99999) 1.0E0_nag_wp/rcond
Write (nout,*)
Write (nout,*) 'Estimate of error bound for computed solutions'
Write (nout,99999) errbnd
Else If (ifail==n+1) Then
!       Matrix A is numerically singular.  Print estimate of
!       reciprocal of condition number and solution
Write (nout,*)
Write (nout,*) 'Estimate of reciprocal of condition number'
Write (nout,99999) rcond
Write (nout,*)
Flush (nout)

ierr = 0
Call x04dbf('General',' ',n,nrhs,b,ldb,'Bracketed',' ','Solution',     &
'Integer',rlabs,'Integer',clabs,80,0,ierr)

Else If (ifail>0 .And. ifail<=n) Then
!       The upper triangular matrix U is exactly singular.  Print
!       details of factorization
Write (nout,*) 'Details of factorization'
Write (nout,*)
Write (nout,*) ' Second superdiagonal of U'
Write (nout,99998) du2(1:n-2)
Write (nout,*)
Write (nout,*) ' First superdiagonal of U'
Write (nout,99998) du(1:n-1)
Write (nout,*)
Write (nout,*) ' Main diagonal of U'
Write (nout,99998) d(1:n)
Write (nout,*)
Write (nout,*) ' Multipliers'
Write (nout,99998) dl(1:n-1)
Write (nout,*)
Write (nout,*) ' Vector of interchanges'
Write (nout,99997) ipiv(1:n)
Else
Write (nout,99996) ifail
End If

99999 Format (8X,1P,E9.1)
99998 Format (4(1X,'(',F7.4,',',F7.4,')',:))
99997 Format (1X,8I9)
99996 Format (1X,' ** F04CCF returned with IFAIL = ',I5)
End Program f04ccfe
```