/* PBXA64 handbook-style C text example: character_classes.
 * classify letters, digits, whitespace, and punctuation. This source deliberately keeps every transformation visible
 * instead of hiding it behind library calls, making it useful for tracing.
 */
int main(void) {
    char s[] = "A9 z!"; int i = 0, letters = 0, digits = 0, spaces = 0; for (i = 0; s[i] != 0; ++i) { if ((s[i] >= 'A' && s[i] <= 'Z') || (s[i] >= 'a' && s[i] <= 'z')) ++letters; else if (s[i] >= '0' && s[i] <= '9') ++digits; else if (s[i] == ' ') ++spaces; } return letters == 2 && digits == 1 && spaces == 1 ? 0 : 1;
}

/* Discussion: inspect the loop bounds, byte classification, and final return
 * value. The bounded-C frontend currently records CIR0200 for all C source;
 * this example remains a real handbook program for the public C surface once
 * that frontend gate is restored. */
