Define macro - Mini Project: Build & Apply

Using #define Macro in C

📖 Scenario: You are writing a simple C program that needs to use a constant value multiple times. Instead of typing the number everywhere, you want to use a macro to make your code easier to read and change.

🎯 Goal: Learn how to create and use a #define macro in C to represent a constant value.

📋 What You'll Learn

Create a macro named PI with the value 3.14

Create a variable radius with the value 5

Calculate the area of a circle using the formula PI * radius * radius

Print the calculated area

💡 Why This Matters

🌍 Real World

Macros help programmers write cleaner code by replacing repeated values with easy names. This makes programs easier to read and update.

💼 Career

Understanding macros is important for C programming jobs, especially in embedded systems, game development, and performance-critical applications.

1

Create a macro for PI

Write a #define macro named PI with the value 3.14 at the top of your program.

C

#include 

// Define PI macro here

int main() {

    return 0;
}

Need a hint?

Use #define PI 3.14 before int main().

2

Create a variable for radius

Inside the main function, create a variable named radius and set it to 5.

C

#include 

#define PI 3.14

int main() {
    // Create radius variable here

    return 0;
}

Need a hint?

Write int radius = 5; inside main.

3

Calculate the area using the macro

Create a variable named area inside main and set it to PI * radius * radius.

C

#include 

#define PI 3.14

int main() {
    int radius = 5;
    // Calculate area here

    return 0;
}

Need a hint?

Use float area = PI * radius * radius; to calculate the area.

4

Print the area

Write a printf statement to display the text "Area: " followed by the value of area with two decimal places.

C

#include 

#define PI 3.14

int main() {
    int radius = 5;
    float area = PI * radius * radius;
    // Print area here

    return 0;
}

Need a hint?

Use printf("Area: %.2f\n", area); to print the area with two decimals.