/* YOUR FILE-HEADER COMMENT HERE */

#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>

/**
 * Calculate and return the letter grade given a score, using the
 * standard formula: 'A' for >= 90, 'B' >= 80, 'C' >= 70, 'D' >= 60,
 * otherwise 'F'.
 *
 * Assume the incoming score is non-negative.
 *
 * @param[in] val Score to evaluate
 * @return Letter grade
 */
extern char calc_grade(int val);

int main(int argc, char *argv[])
{
	/* PART 4: YOUR CODE HERE */

	if (argc < 2) {
		fprintf(stderr, "Need a grade value.\n");
		exit(EXIT_FAILURE);
	} else {
		int val = atoi(argv[1]);
		/* UNCOMMENT THE FOLLOWING LINE WHEN STARTING PART 5
		printf("Value of %d => grade '%c'\n", val, calc_grade(val));
		*/
	}
	return 0;
}