Program exit status and $?

Question

C++ Primer book i read says that

The value returned from main is accessed in a system dependent manner. On both UNIX and Windows systems, afar executing the program you must issue an appropriate echo command. On UNIX we obtain the status by echo $?

So, if the program is

int main ()
{
    return -88;
}

Why does echo $? not return it? (168 is printed upon echo)

Answer 1

It does, sort of. It'll convert the value to an unsigned 8-bit value, though, which is 256 − 88 = 168. That's part of the system-dependent mannerism.