```/* nag_zgbmv (f16sbc) Example Program.
*
* Copyright 2014 Numerical Algorithms Group.
*
* Mark 8, 2005.
*/

#include <stdio.h>
#include <nag.h>
#include <nag_stdlib.h>
#include <nagf16.h>

int main(void)
{

/* Scalars */
Complex       alpha, beta;
Integer       ab_size, exit_status, i, incx, incy, j, kl, ku;
Integer       m, n, pdab, xlen, ylen;

/* Arrays */
Complex       *ab = 0, *x = 0, *y = 0;
char          nag_enum_arg[40];

/* Nag Types */
NagError      fail;
Nag_OrderType order;
Nag_TransType trans;

#ifdef NAG_COLUMN_MAJOR
#define AB(I, J) ab[(J-1)*pdab + ku + I - J]
order = Nag_ColMajor;
#else
#define AB(I, J) ab[(I-1)*pdab + kl + J - I]
order = Nag_RowMajor;
#endif

exit_status = 0;
INIT_FAIL(fail);

printf("nag_zgbmv (f16sbc) Example Program Results\n\n");

/* Skip heading in data file */
scanf("%*[^\n] ");

/* Read the problem dimensions */
scanf("%ld%ld%ld%ld%*[^\n] ",
&m, &n, &kl, &ku);
/* Read the transpose parameter */
scanf("%39s%*[^\n] ", nag_enum_arg);
/* nag_enum_name_to_value (x04nac).
* Converts NAG enum member name to value
*/
trans = (Nag_TransType) nag_enum_name_to_value(nag_enum_arg);
scanf(" ( %lf , %lf ) ( %lf , %lf )%*[^\n] ",
&alpha.re, &alpha.im, &beta.re, &beta.im);
scanf("%ld%ld%*[^\n] ", &incx, &incy);

pdab = kl + ku + 1;
#ifdef NAG_COLUMN_MAJOR
ab_size = pdab*n;
#else
ab_size = pdab*m;
#endif

if (trans == Nag_NoTrans)
{
xlen = MAX(1, 1 + (n - 1)*ABS(incx));
ylen = MAX(1, 1 + (m - 1)*ABS(incy));
}
else
{
xlen = MAX(1, 1 + (m - 1)*ABS(incx));
ylen = MAX(1, 1 + (n - 1)*ABS(incy));
}

if (m > 0 && n > 0)
{
/* Allocate memory */
if (!(ab = NAG_ALLOC(ab_size, Complex)) ||
!(x = NAG_ALLOC(xlen, Complex)) ||
!(y = NAG_ALLOC(ylen, Complex)))
{
printf("Allocation failure\n");
exit_status = -1;
goto END;
}
}
else
{
printf("Invalid m or n\n");
exit_status = 1;
return exit_status;
}

/* Input matrix A and vectors x and y */

for (i = 1; i <= m; ++i)
{
for (j = MAX(1, i-kl); j <= MIN(n, i+ku); ++j)
scanf(" ( %lf , %lf )", &AB(i, j).re, &AB(i, j).im);
scanf("%*[^\n] ");
}
for (i = 1; i <= xlen; ++i)
scanf(" ( %lf , %lf )%*[^\n] ", &x[i - 1].re, &x[i - 1].im);
for (i = 1; i <= ylen; ++i)
scanf(" ( %lf , %lf )%*[^\n] ", &y[i - 1].re, &y[i - 1].im);

/* nag_zgbmv (f16sbc).
* Complex valued band matrix-vector multiply.
*
*/
nag_zgbmv(order, trans, m, n, kl, ku, alpha, ab, pdab, x,
incx, beta, y, incy, &fail);
if (fail.code != NE_NOERROR)
{
printf("Error from nag_zgbmv.\n%s\n", fail.message);
exit_status = 1;
goto END;
}

/* Print output vector y */
printf("%s\n", "  y");
for (i = 1; i <= ylen; ++i)
{
printf("(%11f,%11f)\n", y[i-1].re, y[i-1].im);
}

END:
NAG_FREE(ab);
NAG_FREE(x);
NAG_FREE(y);

return exit_status;
}
```