```/* nag_real_symm_eigensystem (f02abc) Example Program.
*
* Copyright 2014 Numerical Algorithms Group.
*
* Mark 2 revised, 1992.
* Mark 8 revised, 2004.
*/

#include <nag.h>
#include <stdio.h>
#include <nag_stdlib.h>
#include <nagf02.h>

#define A(I, J) a[(I) *tda + J]
#define V(I, J) v[(I) *tdv + J]

int main(void)
{
Integer  exit_status = 0, i, j, n, tda, tdv;
NagError fail;
double   *a = 0, *r = 0, *v = 0;

INIT_FAIL(fail);

printf(
"nag_real_symm_eigensystem (f02abc) Example Program Results\n");
/* Skip heading in data file */
scanf("%*[^\n]");
scanf("%ld", &n);
if (n >= 1)
{
if (!(a = NAG_ALLOC(n*n, double)) ||
!(r = NAG_ALLOC(n, double)) ||
!(v = NAG_ALLOC(n*n, double)))
{
printf("Allocation failure\n");
exit_status = -1;
goto END;
}
tda = n;
tdv = n;
}
else
{
printf("Invalid n.\n");
exit_status = 1;
return exit_status;
}
for (i = 0; i < n; i++)
for (j = 0; j < n; j++)
scanf("%lf", &A(i, j));
/* nag_real_symm_eigensystem (f02abc).
* All eigenvalues and eigenvectors of real symmetric matrix
*/
nag_real_symm_eigensystem(n, a, tda, r, v, tdv,
&fail);
if (fail.code != NE_NOERROR)
{
printf("Error from nag_real_symm_eigensystem (f02abc).\n%s\n",
fail.message);
exit_status = 1;
goto END;
}

printf("Eigenvalues\n");
for (i = 0; i < n; i++)
printf("%9.4f%s", r[i], (i%8 == 7 || i == n-1)?"\n":" ");
printf("Eigenvectors\n");
for (i = 0; i < n; i++)
for (j = 0; j < n; j++)
printf("%9.4f%s", V(i, j), (j%8 == 7 || j == n-1)?"\n":" ");
END:
NAG_FREE(a);
NAG_FREE(r);
NAG_FREE(v);
return exit_status;
}
```