Function declaration and definition - Mini Project: Build & Apply

Function declaration and definition

📖 Scenario: You are creating a simple calculator program in C that adds two numbers. To keep your code organized, you will declare and define a function that adds two integers.

🎯 Goal: Build a C program that declares a function add which takes two integers and returns their sum. Then call this function from main and print the result.

📋 What You'll Learn

Declare a function int add(int a, int b); before main

Define the function add after main

Call the function add inside main with arguments 5 and 7

Print the returned sum using printf

💡 Why This Matters

🌍 Real World

Functions help organize code into reusable blocks, making programs easier to read and maintain.

💼 Career

Understanding function declaration and definition is essential for writing modular and clean C programs in software development.

1

Declare the function

Write a function declaration for add that takes two int parameters named a and b, and returns an int. Place this declaration before the main function.

C

#include 

// Declare the function add here

int main() {
    return 0;
}

Need a hint?

Function declaration tells the compiler about the function name, return type, and parameters before it is used.

2

Define the function

Write the function definition for add after the main function. It should take two int parameters a and b, and return their sum.

C

#include 

int add(int a, int b);

int main() {
    return 0;
}

// Define the function add here

Need a hint?

The function definition includes the code block that returns the sum of a and b.

3

Call the function in main

Inside the main function, call the add function with arguments 5 and 7. Store the result in an int variable named result.

C

#include 

int add(int a, int b);

int main() {
    // Call add with 5 and 7 and store in result
    
    return 0;
}

int add(int a, int b) {
    return a + b;
}

Need a hint?

Store the returned value from add(5, 7) in a variable result.

4

Print the result

Add a printf statement inside main to print the value of result with the message: "Sum is: %d\n".

C

#include 

int add(int a, int b);

int main() {
    int result = add(5, 7);
    // Print the result here
    
    return 0;
}

int add(int a, int b) {
    return a + b;
}

Need a hint?

Use printf("Sum is: %d\n", result); to display the sum.