NAG Library Manual, Mark 28.5
```/* nag_blast_dtrmm (f16yfc) Example Program.
*
* Copyright 2022 Numerical Algorithms Group.
*
* Mark 28.5, 2022.
*/

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

int main(void) {

/* Scalars */
double alpha;
Integer exit_status, i, j, m, n, pda, pdb;

/* Arrays */
double *a = 0, *b = 0;
char nag_enum_arg[40];

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

#ifdef NAG_COLUMN_MAJOR
#define A(I, J) a[(J - 1) * pda + I - 1]
#define B(I, J) b[(J - 1) * pdb + I - 1]
order = Nag_ColMajor;
#else
#define A(I, J) a[(I - 1) * pda + J - 1]
#define B(I, J) b[(I - 1) * pdb + J - 1]
order = Nag_RowMajor;
#endif

exit_status = 0;
INIT_FAIL(fail);

printf("nag_blast_dtrmm (f16yfc) Example Program Results\n\n");

/* Skip heading in data file */
scanf("%*[^\n] ");
/* Read the problem dimensions */
scanf("%" NAG_IFMT "%" NAG_IFMT "%*[^\n] ", &m, &n);

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

scanf("%39s%*[^\n] ", nag_enum_arg);
/* nag_enum_name_to_value (x04nac).
* Converts NAG enum member name to value
*/
side = (Nag_SideType)nag_enum_name_to_value(nag_enum_arg);
scanf("%39s%*[^\n] ", nag_enum_arg);
/* nag_enum_name_to_value (x04nac), see above. */
uplo = (Nag_UploType)nag_enum_name_to_value(nag_enum_arg);
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);
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);

if (side == Nag_LeftSide) {
pda = m;
} else {
pda = n;
}

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

/* Read A from data file */
if (uplo == Nag_Upper) {
for (i = 1; i <= pda; ++i) {
for (j = i; j <= pda; ++j)
scanf("%lf", &A(i, j));
}
scanf("%*[^\n] ");
} else {
for (i = 1; i <= pda; ++i) {
for (j = 1; j <= i; ++j)
scanf("%lf", &A(i, j));
}
scanf("%*[^\n] ");
}

/* Input matrix B */
for (i = 1; i <= m; ++i) {
for (j = 1; j <= n; ++j)
scanf("%lf", &B(i, j));
}

/* nag_blast_dtrmm (f16yfc).
* Triangular matrix-matrix multiply.
*
*/
nag_blast_dtrmm(order, side, uplo, trans, diag, m, n, alpha, a, pda, b, pdb,
&fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_blast_dtrmm (f16yfc).\n%s\n", fail.message);
exit_status = 1;
goto END;
}

/* Print the updated matrix B */
/* 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, m,
n, b, pdb, "Updated matrix B", 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(a);
NAG_FREE(b);

return exit_status;
}
```