NAG Library Manual, Mark 29
```    Program f07pafe

!     F07PAF Example Program Text

!     Mark 29.0 Release. NAG Copyright 2023.

!     .. Use Statements ..
Use nag_library, Only: dspsv, nag_wp, x04ccf
!     .. Implicit None Statement ..
Implicit None
!     .. Parameters ..
Integer, Parameter               :: nin = 5, nout = 6
Character (1), Parameter         :: uplo = 'U'
!     .. Local Scalars ..
Integer                          :: i, ifail, info, j, n
!     .. Local Arrays ..
Real (Kind=nag_wp), Allocatable  :: ap(:), b(:)
Integer, Allocatable             :: ipiv(:)
!     .. Executable Statements ..
Write (nout,*) 'F07PAF Example Program Results'
Write (nout,*)
!     Skip heading in data file

Allocate (ap((n*(n+1))/2),b(n),ipiv(n))

!     Read the upper or lower triangular part of the 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 dspsv is f07paf
Call dspsv(uplo,n,1,ap,ipiv,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
Call x04ccf(uplo,'Non-unit diagonal',n,ap,                             &
'Details of the factorization',ifail)

!       Print pivot indices

Write (nout,*)
Write (nout,*) 'Pivot indices'
Write (nout,99998) ipiv(1:n)

Else
Write (nout,99997) 'The diagonal block ', info, ' of D is zero'
End If

99999 Format ((3X,7F11.4))
99998 Format (1X,7I11)
99997 Format (1X,A,I3,A)
End Program f07pafe
```