NAG Library Manual, Mark 28.6
```/* nag_matop_real_gen_matrix_exp (f01ecc) Example Program.
*
* Copyright 2022 Numerical Algorithms Group.
*
* Mark 28.6, 2022.
*/
/* Pre-processor includes */
#include <math.h>
#include <nag.h>
#include <stdio.h>

int main(void) {
/*Integer scalar and array declarations */
Integer exit_status = 0;
Integer i, j, n;
Integer pda;
NagError fail;
/*Double scalar and array declarations */
double *a = 0;
Nag_OrderType order;

INIT_FAIL(fail);

printf("%s\n",
"nag_matop_real_gen_matrix_exp (f01ecc) Example Program Results");
printf("\n");
/* Skip heading in data file */
scanf("%*[^\n] ");
scanf("%" NAG_IFMT "%*[^\n] ", &n);
#ifdef NAG_COLUMN_MAJOR
pda = n;
#define A(I, J) a[(J - 1) * pda + I - 1]
order = Nag_ColMajor;
#else
pda = n;
#define A(I, J) a[(I - 1) * pda + J - 1]
order = Nag_RowMajor;
#endif
if (!(a = NAG_ALLOC(pda * n, double))) {
printf("Allocation failure\n");
exit_status = -1;
goto END;
}
/* Read A from data file */
for (i = 1; i <= n; i++) {
for (j = 1; j <= n; j++)
scanf("%lf", &A(i, j));
}
scanf("%*[^\n] ");
/* Find exp( A ) */
/*
* nag_matop_real_gen_matrix_exp (f01ecc)
* Real matrix exponential
*/
nag_matop_real_gen_matrix_exp(order, n, a, pda, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_matop_real_gen_matrix_exp (f01ecc).\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,
n, a, pda, "Exp(A)", 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;
}

END:
NAG_FREE(a);

return exit_status;
}
```