Function declaration and definition in C++ - Mini Project: Build & Apply

Function declaration and definition

📖 Scenario: You are creating a simple calculator program 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 and print the result.

📋 What You'll Learn

Declare a function named add that takes two int parameters and returns an int.

Define the function add to return the sum of the two parameters.

Call the add function with the values 5 and 7.

Print the result of the function call.

💡 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 clean, modular code in any software development job.

1

Declare the function add

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

C++

#include 

// Declare the function add here

int main() {
    return 0;
}

Need a hint?

Function declarations end with a semicolon and specify the return type, function name, and parameter types.

2

Define the function add

Write the function definition for add that takes two int parameters a and b, and returns their sum. Place this definition below the main function.

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 function body with curly braces and returns the sum of a and b.

3

Call the function add with values 5 and 7

Inside the main function, create an int variable named result and assign it the value returned by calling add(5, 7).

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?

Call the function by writing add(5, 7) and assign it to result.

4

Print the result

Add a std::cout statement inside main to print the text "Sum: " followed by the value of result, then a newline.

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 std::cout with the insertion operator << to print text and variables.