On a train to a large computer convention, there was a bunch of computer programmers and a bunch of computer engineers. Each of the programmers had a train ticket. The group of engineers had only ONE ticket for all of them. The programmers started laughing, figuring the engineers were going to get caught and thrown off the train.
When one of the engineers, the lookout, said, "Here comes the conductor," all of the engineers went into the bathroom. The programmers were puzzled.
The conductor came aboard, said, "Tickets, please," and got tickets from all the computer programmers. He then went to the bathroom and knocked on the door and said, "Ticket, please." The engineers stuck the ticket under the door. The conductor took it and moved on. A few minutes later, the engineers came out of the bathroom. The programmers felt really stupid.
On the way back from the convention, the group of programmers decided that they would try that method, too. They bought one ticket for the whole group. They met up with the engineers in the same car.
Again, the programmers started snickering at the engineers. This time, NONE of the engineers had tickets. When the lookout said, "Conductor coming!" all the engineers went to one bathroom and all the computer programmers went to the other bathroom.
Before the conductor came on board, one of the engineers left their bathroom, knocked on the programmers bathroom and said, "Ticket, please."