Character frequency

charfreq.c

#include <stdio.h>
#include <string.h>

//maybe works on posix not working for me on windows (S_ISCHR not defined)
//https://comp.os.os2.programmer.porting.narkive.com/s5n0plkf/how-to-set-stdin-stdout-stderr-to-binary-mode
// #include <io.h> // setmode()
// #include <fcntl.h> // O_BINARY
// #include <stdio.h> // FILE, fileno()
// #include <sys/stat.h> // struct stat, fstat(), S_ISCHR()
// static inline void set_bin_mode(FILE *stream)
// {
//     struct stat st;
//     fstat(fileno(stream), &st);
//     if(!S_ISCHR(st.st_mode.))
//     setmode(fileno(stream), O_BINARY);
// }
#define _O_BINARY 0x8000

int main(int argc, char **argv)
{
    int c;
    int freq[256];
    memset((void*)freq, 0, sizeof(freq));
    printf("Top hex digits are the second digit of the character value\nLeft-side hex numbers are the first digit of the character value\nnumbers in the table are the frequence of each character found in stdin.\n");
    _setmode(_fileno(stdin),_O_BINARY);
    //set_bin_mode(stdin);
    while((c = getchar()) != EOF) {
        freq[c]++;
    }
    //header: upper hex digits of the character value
    printf("     ");
    for (int h=0;h<16;h++){
        printf("%6x ",h);
    }
    // header-separator lines
    char *l = "=======";
    printf("\n    %s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s",
           l,l,l,l,l,l,l,l,l,l,l,l,l,l,l,l);
    for (c=0;c<=255;c++) {
        if (!(c & 0xf)) {
            printf("\n%02x: ", c);
        }
        printf("%7d", freq[c]);
    }
    putchar('\n');
    return 0;
}