```/* nag_lapacklin_dgbtrs (f07bec) Example Program.
*
* Copyright 2019 Numerical Algorithms Group.
*
* Mark 27.0, 2019.
*/

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

int main(void)
{
/* Scalars */
Integer i, ipiv_len, j, kl, ku, n, nrhs, pdab, pdb;
Integer exit_status = 0;
NagError fail;
Nag_OrderType order;

/* Arrays */
double *ab = 0, *b = 0;
Integer *ipiv = 0;

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

INIT_FAIL(fail);

printf("nag_lapacklin_dgbtrs (f07bec) Example Program Results\n\n");

/* Skip heading in data file */
scanf("%*[^\n] ");
scanf("%" NAG_IFMT "%" NAG_IFMT "%" NAG_IFMT "%" NAG_IFMT "%*[^\n] ", &n,
&nrhs, &kl, &ku);
ipiv_len = n;
#ifdef NAG_COLUMN_MAJOR
pdab = 2 * kl + ku + 1;
pdb = n;
#else
pdab = 2 * kl + ku + 1;
pdb = nrhs;
#endif

/* Allocate memory */
if (!(ab = NAG_ALLOC((2 * kl + ku + 1) * n, double)) ||
!(b = NAG_ALLOC(nrhs * n, double)) ||
!(ipiv = NAG_ALLOC(ipiv_len, Integer)))
{
printf("Allocation failure\n");
exit_status = -1;
goto END;
}

/* Read A from data file */
for (i = 1; i <= n; ++i) {
for (j = MAX(i - kl, 1); j <= MIN(i + ku, n); ++j)
scanf("%lf", &AB(i, j));
}
scanf("%*[^\n] ");
/* Read B from data file */
for (i = 1; i <= n; ++i) {
for (j = 1; j <= nrhs; ++j)
scanf("%lf", &B(i, j));
}
scanf("%*[^\n] ");

/* Factorize A */
/* nag_lapacklin_dgbtrf (f07bdc).
* LU factorization of real m by n band matrix
*/
nag_lapacklin_dgbtrf(order, n, n, kl, ku, ab, pdab, ipiv, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_lapacklin_dgbtrf (f07bdc).\n%s\n", fail.message);
exit_status = 1;
goto END;
}
/* Compute solution */
/* nag_lapacklin_dgbtrs (f07bec).
* Solution of real band system of linear equations,
* multiple right-hand sides, matrix already factorized by
* nag_lapacklin_dgbtrf (f07bdc)
*/
nag_lapacklin_dgbtrs(order, Nag_NoTrans, n, kl, ku, nrhs, ab, pdab, ipiv,
b, pdb, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_lapacklin_dgbtrs (f07bec).\n%s\n", fail.message);
exit_status = 1;
goto END;
}
/* Print solution */
/* nag_file_print_matrix_real_gen (x04cac).
* Print real general matrix (easy-to-use)
*/
fflush(stdout);
nag_file_print_matrix_real_gen(order, Nag_GeneralMatrix, Nag_NonUnitDiag, n, nrhs,
b, pdb, "Solution(s)", 0, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_file_print_matrix_real_gen (x04cac).\n%s\n", fail.message);
exit_status = 1;
goto END;
}
END:
NAG_FREE(ab);
NAG_FREE(b);
NAG_FREE(ipiv);
return exit_status;
}
```