#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <assert.h>

int main(int argc, char* argv[]) {
    // Create a text file containing "Yo!" plus a null terminator (weird thing to do).  This
    // time, we create the file using an int to get the right bytes in there.  This is just for
    // demonstration to make the point in the lecture, that it's all just bytes.
    FILE* fp = fopen("m.txt", "w");
    int n = 0x00216f59;  // 2191193  ← 0x00216f59 is expressed in big endian byte order
    int* a_n = &n;
    fwrite(a_n, sizeof(*a_n), 1, fp);  // fwrite(…) copies bytes from memory to file.
    fclose(fp); // RULE:  If you open a file, you must close it (once).

    // Read an int from the file.  This only works because the file contains 4 bytes.
    fp = fopen("m.txt", "r");   // mode "r" means we want to read a file.  "a" means append to the end
    int num_from_file;  // will be initialized by fread(…).
    int* a_num_from_file = &num_from_file;
    fread(&num_from_file, sizeof(*a_num_from_file), 1, fp);
    fclose(fp); // RULE:  If you open a file, you must close it (once).
    printf("num_from_file == 0x%08x   #  %d\n", num_from_file, num_from_file);

    // Open file again (for the third time) so we can read the characters as characters.
    fp = fopen("m.txt", "r");
    printf("Here are the character values:\n");
    printf("______________________________\n");
    for(char ch = fgetc(fp); ! feof(fp); ch = fgetc(fp)) {
        printf("character value:  %02x  # %3d  # '%c'\n", ch, ch, ch);
    }
    printf("------------------------------\n");

    return EXIT_SUCCESS;
}
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