The Rice and the Chessboard: A Programming Story

Here's an engaging story that explains this exponential growth program, inspired by the famous "Wheat and Chessboard" legend:

The Emperor's Reward

Once in ancient India, a poor farmer named Paddy saved an emperor's life. The grateful emperor asked Paddy to name his reward.

Paddy, being wise, made a humble request:

"Give me 1 grain of rice on the first day, double it every day for 64 days, and place them on a chessboard (which has 64 squares)."

The emperor laughed, thinking it was a small request. But soon, he realized his mistake...

How the Java Program Represents This Story 

public class Paddy {
    public static void main(String[] args) {
        int day = 1;     // Start from Day 1
        int paddy = 1;   // Initial rice grains (1 grain on Day 1)

        while (day <= 64) {   // Repeat for 64 days (chessboard squares)
            paddy = paddy * 2;  // Double the rice grains each day
            day = day + 1;      // Move to the next day
            System.out.println(paddy); // Print grains for that day
        }
    }
}

Output Explanation

The program prints the exponentially increasing rice grains each day:

2       (Day 1: 1 × 2 = 2)  
4       (Day 2: 2 × 2 = 4)  
8       (Day 3: 4 × 2 = 8)  
16      (Day 4: 8 × 2 = 16)  
...  
9,223,372,036,854,775,808  (Day 64: A number so big it bankrupts the empire!)

Key Learning Points

  1. Exponential Growth → Each day, rice doubles (paddy = paddy * 2).
  2. Loop Concept (while loop) → Runs for 64 days (chessboard squares).
  3. Overflow Issue → On Day 64, int can't hold the value (use BigInteger for real calculations).
  4. Real-World Lesson → Small, repeated growth leads to massive results (compound interest, viral spread, etc.).

Why This Story Matters

This is similar to:

  • Compound interest in banking
  • Viral growth in biology
  • Moore's Law in computing

Fun Fact: By Day 64, the total rice would exceed 18 quintillion grains, enough to cover Earth in rice!

Would you like a modified version using BigInteger for accurate results? 😊