NAG Library Manual, Mark 28.6
```/* nag_lapacklin_dpbsvx (f07hbc) Example Program.
*
* Copyright 2022 Numerical Algorithms Group.
*
* Mark 28.6, 2022.
*/
#include <nag.h>
#include <stdio.h>

int main(void) {

/* Scalars */
double rcond;
Integer exit_status = 0;
Integer i, j, kd, n, nrhs, pdab, pdafb, pdb, pdx;

/* Arrays */
double *ab = 0, *afb = 0, *b = 0, *berr = 0, *ferr = 0;
double *s = 0, *x = 0;
char nag_enum_arg;

/* Nag Types */
NagError fail;
Nag_UploType uplo;
Nag_OrderType order;
Nag_EquilibrationType equed;

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

INIT_FAIL(fail);

printf("nag_lapacklin_dpbsvx (f07hbc) Example Program Results\n\n");
/* Skip heading in data file */
scanf("%*[^\n]");
scanf("%" NAG_IFMT "%" NAG_IFMT "%" NAG_IFMT "%*[^\n]", &n, &kd, &nrhs);
if (n < 0 || nrhs < 0 || kd < 0) {
printf("Invalid n, kd or nrhs\n");
exit_status = 1;
goto END;
}
scanf(" %39s%*[^\n]", nag_enum_arg);
/* nag_enum_name_to_value (x04nac).
* Converts NAG enum member name to value
*/
uplo = (Nag_UploType)nag_enum_name_to_value(nag_enum_arg);

/* Allocate memory */
if (!(ab = NAG_ALLOC((kd + 1) * n, double)) ||
!(afb = NAG_ALLOC((kd + 1) * n, double)) ||
!(b = NAG_ALLOC(n * nrhs, double)) || !(berr = NAG_ALLOC(nrhs, double)) ||
!(ferr = NAG_ALLOC(nrhs, double)) || !(s = NAG_ALLOC(n, double)) ||
!(x = NAG_ALLOC(n * nrhs, double))) {
printf("Allocation failure\n");
exit_status = -1;
goto END;
}

pdab = kd + 1;
pdafb = kd + 1;
#ifdef NAG_COLUMN_MAJOR
pdb = n;
pdx = n;
#else
pdb = nrhs;
pdx = nrhs;
#endif

/* Read the upper or lower triangular part of the band matrix A from
* data file.
*/
if (uplo == Nag_Upper)
for (i = 1; i <= n; ++i)
for (j = i; j <= MIN(n, i + kd); ++j)
scanf("%lf", &AB_UPPER(i, j));
else
for (i = 1; i <= n; ++i)
for (j = MAX(1, i - kd); j <= i; ++j)
scanf("%lf", &AB_LOWER(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]");

/* Solve the equations AX = B for X using nag_lapacklin_dpbsvx (f07hbc). */
fflush(stdout);
nag_lapacklin_dpbsvx(order, Nag_EquilibrateAndFactor, uplo, n, kd, nrhs, ab,
pdab, afb, pdafb, &equed, s, b, pdb, x, pdx, &rcond,
ferr, berr, &fail);
if (fail.code != NE_NOERROR && fail.code != NE_SINGULAR) {
printf("Error from nag_lapacklin_dpbsvx (f07hbc).\n%s\n", fail.message);
exit_status = 1;
goto END;
}

/* Print solution using nag_file_print_matrix_real_gen (x04cac). */
nag_file_print_matrix_real_gen(order, Nag_GeneralMatrix, Nag_NonUnitDiag, n,
nrhs, x, pdx, "Solution(s)", 0, &fail);
if (fail.code != NE_NOERROR) {
printf("\nError from nag_file_print_matrix_real_gen (x04cac).\n%s\n",
fail.message);
exit_status = 1;
goto END;
}

/* Print error bounds, condition number and the form of equilibration */
printf("\nBackward errors (machine-dependent)\n");
for (j = 0; j < nrhs; ++j)
printf("%11.1e%s", berr[j], j % 7 == 6 ? "\n" : " ");

printf("\n\nEstimated forward error bounds (machine-dependent)\n");
for (j = 0; j < nrhs; ++j)
printf("%11.1e%s", ferr[j], j % 7 == 6 ? "\n" : " ");

printf("\n\nEstimate of reciprocal condition number\n%11.1e\n\n", rcond);
if (equed == Nag_NoEquilibration)
printf("A has not been equilibrated\n");
else if (equed == Nag_RowAndColumnEquilibration)
printf("A has been row and column scaled as diag(S)*A*diag(S)\n");
if (fail.code == NE_SINGULAR) {
printf("Error from nag_lapacklin_dpbsvx (f07hbc).\n%s\n", fail.message);
exit_status = 1;
}
END:
NAG_FREE(ab);
NAG_FREE(afb);
NAG_FREE(b);
NAG_FREE(berr);
NAG_FREE(ferr);
NAG_FREE(s);
NAG_FREE(x);

return exit_status;
}

#undef AB_UPPER
#undef AB_LOWER
#undef B
```