Challenge 1: Three Named Flags, Combined and Checked — Possible Solution
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#include <stdio.h>

#define FLAG_READ  (1 << 0)
#define FLAG_WRITE (1 << 1)
#define FLAG_EXEC  (1 << 2)

int main() {
    unsigned int perms = FLAG_READ | FLAG_WRITE | FLAG_EXEC;

    printf("READ:  %s\n", (perms & FLAG_READ)  ? "set" : "not set");
    printf("WRITE: %s\n", (perms & FLAG_WRITE) ? "set" : "not set");
    printf("EXEC:  %s\n", (perms & FLAG_EXEC)  ? "set" : "not set");

    return 0;
}

Output:

    READ:  set
    WRITE: set
    EXEC:  set

WHY THIS WORKS AS AN ANSWER
------------------------------
Each flag occupies a distinct bit position (1<<0, 1<<1, 1<<2 -- bits 0,
1, and 2 respectively), so OR-ing all three together sets each bit
independently with no overlap or interference, exactly matching the
chapter's own FLAG_A/FLAG_B/FLAG_C pattern; checking each one with AND
against perms correctly isolates just that bit's contribution,
confirming all three read as set.