/* A program to print a table showing the numbers 1..10 and their
factorials, then the sum of these numbers and the sum of the factorials.
*/

#include <stdio.h>

/*** global variables ***/
int next_number,              /* The next number to be processed */
    sum_numbers;              /* progressive sum */
long factorial,               /* factorial of latest number to process */
     sum_factorials;          /* sum of the factorials */

/*** function declarations ***/
void print_heading (void);
void update_totals_and_factorial (void);

/*** Function definitions ***/

main () {

    /* Output the column headings */
    print_heading();

    /* Set totals and factorial variables to initial values. */
    factorial = 1;                   /* factorial(0) is 1 */
    sum_factorials = sum_numbers = 0;/* sum of nothing is zero.  (This
                                        statement shows how you can assign
                                        a value (0, here) to two or more
                                        variables in one statement.) */

    /* In a loop, print the detail lines in the table */
    next_number = 1;  /* first number to process */
    while (next_number <= 10) {     /* Keep going while the next_number
                                       is within the range we require. */

        /* At this point:
         *       factorial == (next_number-1)!     (! is factorial fn)
         *       sum_numbers == sum of 1..(next_number-1)
         *       sum_factorials == sum of 1! .. (next_number-1)!
         */

        update_totals_and_factorial();

        /* Print a detail line for the number prepared */
        printf("%4d%11ld\n", next_number, factorial);

        next_number = next_number + 1; /* update loop counter */
    }                                  /* End of the while loop */
    /* After the loop:
     *       factorial == 10!
     *       sum_numbers == sum of 1..10
     *       sum_factorials == sum of 1! .. 10!
     */

    /*** Now print the grand totals. ***/
    printf (
        "================\nSum of 1..%d: %d\n",
        10,
        sum_numbers
    );
    printf("Sum of factorials: %ld\n", sum_factorials);

} /* of main */

void print_heading (void) {
    /* prints the headings over the columns in the table */
    printf("Number  Factorial\n======  =========\n");
}

void update_totals_and_factorial (void) {
/*     Updates factorial and sum for the next number in ascending order.
 *     On entry: factorial and sums are correct for 1..(next_number-1).
 *     On exit:  factorial and sums are correct for 1..next_number.
 */
    factorial = factorial * next_number;
    sum_numbers = sum_numbers + next_number;
    sum_factorials = sum_factorials + factorial;
}