Which port for DHCP?

For a long time, I never remembered which UDP port was for the DHCP server and which was for the client. I finally came up with a trick... you have to have a server in place before you can have any clients, right? Therefore, the first port, 67, is the port the server listens on. The second port, 68, is the source port the client uses.

Previous working directory in Windows Command Prompt

Using bash in *nix has a handy feature: If you are in one directory and you switch to another one, you can use   cd -  to go back to the pr...