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