What does `exit()` send `status` to, the parent process or the OS kernel?

In Linux,

#include <stdlib.h>
void exit(int status);

What does exit() send status to, the parent process or the OS kernel?

APUE says that

exit() performs certain cleanup processing and then returns to the kernel.

But when I run a program in shell, the program returns its exit status to the shell which is its parent process.

Answer

As you’re probably aware, Linux (like most Operating Systems) keeps processes separate. That’s why the result of exit is passed via the kernel to the parent process.