NAG Library Manual, Mark 27.3
```/* nag_lapacklin_dspsv (f07pac) Example Program.
*
* Copyright 2021 Numerical Algorithms Group.
*
* Mark 27.3, 2021.
*/

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

int main(void) {

/* Scalars */
Integer exit_status = 0, i, j, n, nrhs, pdb;

/* Arrays */
double *ap = 0, *b = 0;
Integer *ipiv = 0;
char nag_enum_arg[40];

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

#ifdef NAG_COLUMN_MAJOR
#define A_UPPER(I, J) ap[J * (J - 1) / 2 + I - 1]
#define A_LOWER(I, J) ap[(2 * n - J) * (J - 1) / 2 + I - 1]
#define B(I, J) b[(J - 1) * pdb + I - 1]
order = Nag_ColMajor;
#else
#define A_LOWER(I, J) ap[I * (I - 1) / 2 + J - 1]
#define A_UPPER(I, J) ap[(2 * n - I) * (I - 1) / 2 + J - 1]
#define B(I, J) b[(I - 1) * pdb + J - 1]
order = Nag_RowMajor;
#endif

INIT_FAIL(fail);

printf("nag_lapacklin_dspsv (f07pac) Example Program Results\n\n");

/* Skip heading in data file */
scanf("%*[^\n]");
scanf("%" NAG_IFMT "%" NAG_IFMT "%*[^\n]", &n, &nrhs);
if (n < 0 || nrhs < 0) {
printf("Invalid n 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 (!(ap = NAG_ALLOC(n * (n + 1) / 2, double)) ||
!(b = NAG_ALLOC(n * nrhs, double)) || !(ipiv = NAG_ALLOC(n, Integer))) {
printf("Allocation failure\n");
exit_status = -1;
goto END;
}

#ifdef NAG_COLUMN_MAJOR
pdb = n;
#else
pdb = nrhs;
#endif

/* Read the triangular part of the matrix A from data file */
if (uplo == Nag_Upper)
for (i = 1; i <= n; ++i)
for (j = i; j <= n; ++j)
scanf("%lf", &A_UPPER(i, j));
else
for (i = 1; i <= n; ++i)
for (j = 1; j <= i; ++j)
scanf("%lf", &A_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_dspsv (f07pac). */
nag_lapacklin_dspsv(order, uplo, n, nrhs, ap, ipiv, b, pdb, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_lapacklin_dspsv (f07pac).\n%s\n", fail.message);
exit_status = 1;
goto END;
}

/* Print solution */
printf("   Solution\n");
for (i = 1; i <= n; ++i) {
for (j = 1; j <= nrhs; ++j)
printf(" %10.4f%s", B(i, j), j % 7 == 0 ? "\n" : "");
printf("\n");
}

END:
NAG_FREE(ap);
NAG_FREE(b);
NAG_FREE(ipiv);

return exit_status;
}

#undef A_UPPER
#undef A_LOWER
#undef B
```