⓯ Program to Find the Area of a Circle in C (with complete explanation)

🟢 Program to Find the Area of a Circle in C

📌 Problem Statement

Write a C program to calculate the area of a circle when the radius is given by the user.

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📘 Theory

The area of a circle is calculated using the formula:

$$\text{Area}=\pi \times r\times r$$

Where:

• π (pi) ≈ 3.14159

• r = radius of the circle

Since the result may be a decimal value, we use the float data type.

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🧠 Algorithm

1. Start

2. Declare variables radius and area

3. Read the value of radius from the user

4. Calculate area using the formula

5. Display the result

6. End

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💻 C Program

#include <stdio.h>

int main()
{
    float radius, area;
    const float PI = 3.14159;

    // Taking input from user
    printf("Enter the radius of the circle: ");
    scanf("%f", &radius);

    // Calculating area
    area = PI * radius * radius;

    // Displaying result
    printf("Area of the circle = %.2f", area);

    return 0;
}

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🔍 Explanation of the Code

• #include <stdio.h>
  → Includes standard input-output functions.

• float radius, area;
  → Used to store decimal values.

• const float PI = 3.14159;
  → Constant value of π.

• scanf("%f", &radius);
  → Takes radius as input from the user.

• area = PI * radius * radius;
  → Formula to calculate the area.

• printf("Area of the circle = %.2f", area);
  → Displays the area up to 2 decimal places.

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▶️ Sample Output

Input

Enter the radius of the circle: 7

Output

Area of the circle = 153.94

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✅ Conclusion

This program efficiently calculates the area of a circle using a simple mathematical formula. It is beginner-friendly and commonly asked in C programming interviews and exams.

📘 C Programming Series – What’s Next?
👉 In the next post of this series, we will learn how to print multiplication table of a number with complete explanation and output examples. Stay tuned! 🚀