create readme.md file for that problems

Author: iamAntimPal

Interview/Python/Solutions/140+ Basic Python Programs/Program 16/README.md

@@ -1 +1,93 @@
-# Program16
+# ✨ Factorial Calculator (Python)
+
+This Python program calculates the **factorial** of a given non-negative integer using a `for` loop.
+
+---
+
+## 📌 Problem Statement
+
+**Write a Python program to find the factorial of a number.**
+
+---
+
+## ℹ️ What is a Factorial?
+
+The **factorial** of a number `n` (written as `n!`) is the product of all positive integers from `1` to `n`.
+
+### ✅ Examples:
+
+- `5! = 5 × 4 × 3 × 2 × 1 = 120`
+- `0! = 1` (by definition)
+
+---
+
+## ✅ Sample Code
+
+```python
+# Python program to find the factorial of a number
+
+# Input from user
+num = int(input("Enter a non-negative integer: "))
+
+# Factorial calculation
+if num < 0:
+    print("Factorial is not defined for negative numbers.")
+else:
+    factorial = 1
+    for i in range(1, num + 1):
+        factorial *= i
+    print(f"The factorial of {num} is {factorial}")
+```
+
+---
+
+## ▶️ Example Runs
+
+```bash
+Enter a non-negative integer: 5
+The factorial of 5 is 120
+```
+
+```bash
+Enter a non-negative integer: 0
+The factorial of 0 is 1
+```
+
+```bash
+Enter a non-negative integer: -3
+Factorial is not defined for negative numbers.
+```
+
+---
+
+## 🚀 How to Run
+
+1. Save the code in a file named `factorial.py`
+2. Run the script using:
+
+   ```bash
+   python factorial.py
+   ```
+
+---
+
+## 📁 Suggested Project Structure
+
+```
+factorial/
+├── factorial.py
+└── README.md
+```
+
+---
+
+## 💡 You Can Try
+
+- Implement the factorial using **recursion**.
+- Use the built-in `math.factorial()` function for comparison.
+- Plot the growth of factorial values using `matplotlib`.
+
+---
+
+Happy Coding! 🔢🎯
+