/*
    printing_bytes.c
    Jeff Ondich, 23 Jan 2022, originally named printing-bytes.c
    Modified by Tanya Amert for Fall 2024

    An exploration of the arduous business of printing a single byte
    as a two-digit hexadecimal number. C's automatic typecasting causes
    surprising problems.
 */

#include <stdio.h>

/*
 * This function demonstrates various ways of printing a char's value
 * in hexadecimal. At no time do the bits in the relevant byte change,
 * but several of these printing options give us an answer we don't want.
 */
int main(int argc, char *argv[])
{
    // printf expects an int for %x. If it sees something that isn't
    // already an int (e.g., a char), printf does typecasting to transform the
    // argument to an int. And when a char gets typecast to an int, the
    // additional 24 bits get filled with whatever the leftmost bit of the
    // char is. So if the leftmost bit of the char is 1, then the int ends up as
    // a negative number, and in hex that looks like 0xFFFFFF?? where
    // the ?? is the contents of the original char.
    char ch = 0xc3;  // binary: 1100 0011
    int n = (int)ch; // expanded to 32 bits instead of 8
    printf("0x%x\n", n);
    printf("0x%x\n", ch);
    printf("0x%x\n", (unsigned char)ch); // yay! this one does what we want!
    printf("0x%x\n", (unsigned int)ch);
    printf("0x%x\n", ch & 0xFF); // yay! this one too!

    // Stay tuned.  Soon, we're going to look at the assembly generated
    // by this program to figure out why it works this way.

    return 0;
}