As each studio can freely generate its own PC format, it cannot be used universally to identify the show and episode.
While, in general, television episodes are filmed in the order they are intended to be aired in, there are circumstances in which this is not the case.
In these instances, the production codes can be useful in determining the writers' original intentions.
Some "stand-alone" shows, such as The Simpsons, Law & Order or SpongeBob SquarePants, may air episodes in radically different order to how they are produced, because character development and continuity are not major aspects of production.
A good example of this is The X-Files, which filmed episodes out of order in its fifth and sixth seasons to accommodate the shooting schedules of main stars Gillian Anderson and David Duchovny.