```/* nag_dtbsv (f16pkc) Example Program.
*
* NAGPRODCODE Version.
*
* Copyright 2016 Numerical Algorithms Group.
*
* Mark 26, 2016.
*/

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

int main(void)
{

/* Scalars */
double alpha;
Integer exit_status, i, incx, j, kd, n, pdab, xlen;

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

/* Nag Types */
NagError fail;
Nag_OrderType order;
Nag_TransType trans;
Nag_UploType uplo;
Nag_DiagType diag;

#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]
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]
order = Nag_RowMajor;
#endif

exit_status = 0;
INIT_FAIL(fail);

printf("nag_dtbsv (f16pkc) Example Program Results\n\n");

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

/* Read the problem dimensions */
scanf("%" NAG_IFMT "%" NAG_IFMT "%*[^\n] ", &n, &kd);

/* Read the uplo storage parameter */
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);
/* Read the transpose parameter */
scanf("%39s%*[^\n] ", nag_enum_arg);
/* nag_enum_name_to_value (x04nac), see above. */
trans = (Nag_TransType) nag_enum_name_to_value(nag_enum_arg);
/* Read the unit-diagonal parameter */
scanf("%39s%*[^\n] ", nag_enum_arg);
/* nag_enum_name_to_value (x04nac), see above. */
diag = (Nag_DiagType) nag_enum_name_to_value(nag_enum_arg);

scanf("%lf%*[^\n] ", &alpha);
scanf("%" NAG_IFMT "%*[^\n] ", &incx);

pdab = kd + 1;
xlen = MAX(1, 1 + (n - 1) * ABS(incx));

if (n > 0) {
/* Allocate memory */
if (!(ab = NAG_ALLOC(pdab * n, double)) || !(x = NAG_ALLOC(xlen, double)))
{
printf("Allocation failure\n");
exit_status = -1;
goto END;
}
}
else {
printf("Invalid n\n");
exit_status = 1;
return exit_status;
}

/* Input matrix AB and vector x */

if (uplo == Nag_Upper) {
for (i = 1; i <= n; ++i) {
if (diag == Nag_NonUnitDiag)
scanf("%lf", &AB_UPPER(i, i));
for (j = i + 1; j <= MIN(i + kd, n); ++j)
scanf("%lf", &AB_UPPER(i, j));
}
scanf("%*[^\n] ");
}
else {
for (i = 1; i <= n; ++i) {
for (j = MAX(1, i - kd); j < i; ++j)
scanf("%lf", &AB_LOWER(i, j));
if (diag == Nag_NonUnitDiag)
scanf("%lf", &AB_LOWER(i, i));
}
scanf("%*[^\n] ");
}
for (i = 0; i < xlen; ++i)
scanf("%lf%*[^\n] ", &x[i]);

/* nag_dtbsv (f16pkc).
* Solution of real triangular band system of linear equations.
*
*/
nag_dtbsv(order, uplo, trans, diag, n, kd, alpha, ab, pdab, x, incx, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_dtbsv (f16pkc).\n%s\n", fail.message);
exit_status = 1;
goto END;
}

/* Print output vector x */
printf("%s\n", " Solution x:");
for (i = 0; i < xlen; ++i) {
printf("%11f\n", x[i]);
}

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

return exit_status;
}
```