A novice monk had just started learning assembly programming when he was troubled by doubt. He approached his master and asked:
"Master, how do I know which is code and which is data?"
The master who was meditating, opened his eyes, smiled, and said:
"Each is the other, yet neither is either."
"Master, I do not understand.", said the disciple.
The master then brought out two identical pots and said. "Take these. Fill one with the water from the lake, and fill the other with water from the stream that flows into the lake. Then bring them to me."
The monk bowed and took the pots. He walked to the lake, which was some distance away and filled it with water from the lake. Then he walked around the side of the lake until he found the stream that fed water into the lake. He used this water to fill the second pot and then brought both pots back to his master and set them at his feet. The master looked at the pots, and then back to his disciple and said "Now go. You may come back tomorrow morning."
The disciple came back the next morning to find his master standing with the two pots. He held up both the pots and then threw them to the opposite sides of the room. The pots smashed, and the water from both pots flowed towards the center of the room, forming a puddle.
The master then said, "Which pot contained water from the stream? Which pot contained water from the lake?" He then pointed to the growing puddle that was forming in the middle of the room. "Which part of the puddle contains water from the stream? Which part contains water from the lake?"
In that moment, the novice was enlightened.