```/* nag_complex_eigensystem_sel (f02gcc) Example Program.
*
* Copyright 2017 Numerical Algorithms Group.
*
* Mark 26.2, 2017.
*
*/

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

#define MMAX 3

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

int main(void)
{

Complex *a = 0, *v = 0, *w = 0;
Integer exit_status = 0, i, j, m, mest = MMAX, n, tda, tdv;
NagError fail;
double wl, wu;

INIT_FAIL(fail);

printf("nag_complex_eigensystem_sel (f02gcc) Example Program Results\n");

/* Skip heading in data file */
scanf("%*[^\n]");
scanf("%" NAG_IFMT "%lf%lf%*[^\n] ", &n, &wl, &wu);
if (n >= 0) {
if (!(a = NAG_ALLOC(n * n, Complex)) ||
!(v = NAG_ALLOC(n * mest, Complex)) || !(w = NAG_ALLOC(n, Complex)))
{
printf("Allocation failure\n");
exit_status = -1;
goto END;
}
tda = n;
tdv = mest;
}
else {
printf("Invalid n.\n");
exit_status = 1;
return exit_status;
}

/* Read a from data file */
for (i = 0; i < n; ++i)
for (j = 0; j < n; ++j)
scanf(" ( %lf, %lf ) ", &A(i, j).re, &A(i, j).im);

/* Compute selected eigenvalues and eigenvectors of A */

/* nag_complex_eigensystem_sel (f02gcc).
* Computes selected eigenvalues and eigenvectors of a
* complex general matrix
*/
nag_complex_eigensystem_sel(Nag_Select_Modulus, n, a, tda, wl, wu, mest, &m,
w, v, tdv, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_complex_eigensystem_sel (f02gcc).\n%s\n",
fail.message);
exit_status = 1;
goto END;
}

printf("\n\nEigenvalues\n\n");
for (i = 0; i < m; ++i)
printf("(%7.4f, %7.4f)%s", w[i].re, w[i].im,
(i + 1) % 2 == 0 ? "\n" : " ");

printf("\nEigenvectors\n");
for (i = 1; i <= m; i++)
printf("%15" NAG_IFMT "%s", i, i % m == 0 ? "\n" : "");

for (i = 0; i < n; i++) {
printf("%" NAG_IFMT "  ", i + 1);
for (j = 0; j < m; j++)
printf("(%8.4f, %8.4f)%s", V(i, j).re,
V(i, j).im, (j + 1) % m == 0 ? "\n" : "  ");
}
END:
NAG_FREE(a);
NAG_FREE(v);
NAG_FREE(w);
return exit_status;
}
```