```/* nag_dstevr (f08jdc) Example Program.
*
* Copyright 2017 Numerical Algorithms Group.
*
* Mark 26.2, 2017.
*/

#include <stdio.h>
#include <nag.h>
#include <nag_stdlib.h>
#include <nagf08.h>
#include <nagx04.h>

int main(void)
{
/* Scalars */
double abstol, vl = 0.0, vu = 0.0;
Integer exit_status = 0, i, il, iu, j, m, n, pdz;
/* Arrays */
double *d = 0, *e = 0, *w = 0, *z = 0;
Integer *isuppz = 0;
/* Nag Types */
Nag_OrderType order;
NagError fail;

#ifdef NAG_COLUMN_MAJOR
order = Nag_ColMajor;
#else
order = Nag_RowMajor;
#endif

INIT_FAIL(fail);

printf("nag_dstevr (f08jdc) Example Program Results\n\n");

/* Skip heading in data file and read n and the lower and upper
* indices of the eigenvalues to be found.
*/
scanf("%*[^\n]");
scanf("%" NAG_IFMT "%" NAG_IFMT "%" NAG_IFMT "%*[^\n]", &n, &il, &iu);

m = iu - il + 1;
pdz = n;

/* Allocate memory */
if (!(d = NAG_ALLOC(n, double)) ||
!(e = NAG_ALLOC(n - 1, double)) ||
!(w = NAG_ALLOC(n, double)) ||
!(z = NAG_ALLOC(n * n, double)) || !(isuppz = NAG_ALLOC(n, Integer)))
{
printf("Allocation failure\n");
exit_status = -1;
goto END;
}

/* Read the diagonal and off-diagonal elements of the matrix A
* from data file.
*/
for (i = 0; i < n; ++i)
scanf("%lf", &d[i]);
scanf("%*[^\n]");

for (i = 0; i < n - 1; ++i)
scanf("%lf", &e[i]);
scanf("%*[^\n]");

/* Set the absolute error tolerance for eigenvalues.
* With abstol set to zero, the default value is used instead.
*/
abstol = 0.0;

/* nag_dstevr (f08jdc).
* Solve the symmetric tridiagonal eigenvalue problem.
*/
nag_dstevr(order, Nag_DoBoth, Nag_Indices, n, d, e, vl, vu, il, iu, abstol,
&m, w, z, pdz, isuppz, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_dstevr (f08jdc).\n%s\n", fail.message);
exit_status = 1;
goto END;
}

/* Print solution */
printf("Selected eigenvalues\n   ");
for (j = 0; j < m; ++j)
printf("%8.4f%s", w[j], (j + 1) % 8 == 0 ? "\n" : " ");
printf("\n\n");

/* nag_gen_real_mat_print (x04cac).
* Print selected eigenvectors.
*/
fflush(stdout);
nag_gen_real_mat_print(order, Nag_GeneralMatrix, Nag_NonUnitDiag, n,
m, z, pdz, "Selected eigenvectors", 0, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_gen_real_mat_print (x04cac).\n%s\n", fail.message);
exit_status = 1;
goto END;
}

END:
NAG_FREE(d);
NAG_FREE(e);
NAG_FREE(w);
NAG_FREE(z);
NAG_FREE(isuppz);

return exit_status;
}
```