Flipping burgers and bits is not same

How do we flip bits in a integer from p1 to p2 locations in C? Here is the macro for it.
#define flip_bits(x, p1, p2) (x ^ (((unsigned int)~0 >> ((sizeof(int) * 8) - (p2-p1+1))) << p1))

Traceroute - How it works?

Traceroute is a Linux/Unix utility that is used to find all the routers along the destination host. It works by sending 3 UDP datagrams with destination ports numbers from 33434 to 33534 at a time
with TTL value starting with 1 till the destination is reached. Each router along the way send back ICMP message when it sees TTL value = 1.
A similar utility used in Windows, tracert does not use UDP packets but ICMP echo request (type 8) instead as in the case of ping.

Closures

Closures achieve lexical scoping.