```/* nag_bessel_zeros (s17alc) Example Program.
*
* Copyright 2017 Numerical Algorithms Group.
*
* NAG C Library
*
* Mark 26.1, 2017.
*
*/

#include <stdio.h>
#include <math.h>
#include <nag.h>
#include <nag_stdlib.h>
#include <nags.h>
#include <nagx02.h>

int main(void)
{

#define NMAX 100

Integer exit_status = 0, i, mode, n;
NagError fail;
double a, rel, *x = 0;

INIT_FAIL(fail);

/* Skip heading in data file */
scanf("%*[^\n]");
printf("nag_bessel_zeros (s17alc) Example Program Results\n\n");

if (!(x = NAG_ALLOC(NMAX, double)))
{
printf("Allocation failure\n");
exit_status = -1;
goto END;
}
/* nag_machine_precision (x02ajc).
* The machine precision
*/
rel = sqrt(nag_machine_precision);
scanf("%lf %" NAG_IFMT " %" NAG_IFMT "", &a, &n, &mode);
/* nag_bessel_zeros (s17alc).
* Zeros of Bessel functions J_alpha(x), (J_alpha')(x),
* Y_alpha(x) or (Y_alpha')(x)
*/
nag_bessel_zeros(a, n, mode, rel, x, &fail);

if (fail.code == NE_NOERROR) {
printf("   a   n   mode\n");
printf(" %4.1f%3" NAG_IFMT "%6" NAG_IFMT "\n\n", a, n, mode);
if (mode == 1)
printf("Leading n positive zeros of J\n");
else if (mode == 2)
printf("Leading n positive zeros of Y\n");
else if (mode == 3) {
if (a == 0.0)
printf("Leading n non-negative zeros of J'\n");
else
printf("Leading n positive zeros of J'\n");
}
else if (mode == 4)
printf("Leading n positive zeros of Y'\n\n");
for (i = 0; i <= n - 1; ++i)
printf("  x = %13.4e\n", x[i]);
printf("\n");
}
else {
printf("Error from nag_bessel_zeros (s17alc).\n%s\n", fail.message);
exit_status = 1;
goto END;
}
END:
NAG_FREE(x);
return exit_status;
}
```