Challenge 9 (C)

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

#define MAX_STR 2
#define ALPHA_LEN 26

int main(void) {
    short int sumdigit = 0;
    short int alpha[ALPHA_LEN] = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
    char s[2];
    int i;
    FILE *f;

    f = fopen("challenge9_list.txt", "r");
    while (fscanf(f, "%s", s) != EOF) {
        if (isdigit(s[0])) sumdigit += (short) s[0] - (short) '0';
        else if (isalpha(s[0]))
                if (islower(s[0])) alpha[(short) s[0] - (short) 'a']++;
    }
    fclose(f);

    printf("Sum = %hd\n", sumdigit);
    for(i=0; i < ALPHA_LEN; i++) {
        if (alpha[i] != 0)
            printf("%c = %hd\n", (char) (i + (short) 'a'), alpha[i]);
    }
}