count occurrences of a-z in short phrases

letters.c

// letters.c - 2019 - brian swetland
#include <ctype.h>
#include <stdio.h>
#include <string.h>

int main(int argc, char** argv) {
    char *x, line[256];
    unsigned count[256];
    unsigned extra, missing, n;
    while ((x = fgets(line, sizeof(line), stdin)) != NULL) {
        memset(count, 0, sizeof(count));
        while (*x != 0) count[tolower(*x++)]++;
        for (n = 'a'; n <= 'z'; n++) printf("%c", n);
        printf(" %s", line);
        for (extra = 0, missing = 0, n = 'a'; n <= 'z'; n++) {
            if (count[n] == 0) missing++;
            if (count[n] > 1) extra++;
            printf("%u", count[n]);
        }
        printf(" -%u +%u\n", missing, extra);
    }
    return 0;
}

// abcdefghijklmnopqrstuvwxyz the quick brown fox jumps over the lazy dog
// 11113112111111411212211111 -0 +6
//
// abcdefghijklmnopqrstuvwxyz pack my box with five dozen liquor jugs
// 11112111311111311111211111 -0 +4
//
// abcdefghijklmnopqrstuvwxyz sphinx of black quartz, judge my vow
// 21111111111111211111211111 -0 +3
//
// abcdefghijklmnopqrstuvwxyz hello, world
// 00011001000300200100001000 -19 +2