void sortdata (competitor_data *competitors) {
/* insertion sort the data items...it's more efficient than a bubble sort and not too complex */
        int x = 0, y = 0;
        /* a temporary data item to hold the item currently being sorted */
        struct competitor_data tempitem;
        /* variables to hold the total catch size for the 'current' data items being compared */
        int this_total_weight = 0, next_total_weight = 0;

        for (x = 1; x < NUM_COMPETITORS; x++) {
                y = x;
                tempitem = competitors[x];

                /* need to calculate the total weights
                 * to compare, once each time the outer loop
                 * for 'this' item, and once each time round
                 * the loop for the 'next' item
                 */
                this_total_weight = competitors[y].river_weight + competitors[y].sea_weight + competitors[y].fly_weight;
                next_total_weight = competitors[y-1].river_weight + competitors[y-1].sea_weight + competitors[y-1].fly_weight;

                while ((y > 0) && (this_total_weight > next_total_weight)) {
                        competitors[y] = competitors[y-1];
                        y--;
                        next_total_weight = competitors[y-1].river_weight + competitors[y-1].sea_weight + competitors[y-1].fly_weight;
                }
                competitors[y] = tempitem;
        }
}