cpp_001_Introduction to Functions

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Function Syntax in C++

Before diving into the examples, let’s first look at the basic syntax for defining a function in C++:

return_type function_name(parameters) {
    // Function body
    // perform the task here
}

• return_type: The data type the function will return. If the function doesn't return anything, it’s marked as void.
• function_name: The name of the function, which you use to call it in the program.
• parameters: The values or variables passed into the function to perform its task (also known as arguments). If no parameters are needed, it will be empty.
• function body: The block of code enclosed in { } where the task is performed.

Once the function is defined, you can call it in your program by simply using the function name followed by arguments (if any).

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Example 1: Simple Function (No Arguments, No Return Value)

Aim: Define a function that performs a task (prints a message) without taking any input or returning any value.

Code:

#include <iostream>
using namespace std;

// Function declaration
void greet() {
    cout << "Hello, World!" << endl;
}

int main() {
    greet();  // Function call
    return 0;
}

Expected Output:

Hello, World!

Explanation:

• Function: greet() is a simple function that does not take any input or return any output. It simply prints a message "Hello, World!".
• Calling the Function: In main(), we call greet() to execute the code inside it.
• Expected Output: The program will print Hello, World! when executed.

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Example 2: Function with Arguments

Aim: Create a function that takes parameters (arguments) as input and performs a task using those arguments.

#include <iostream>
using namespace std;

// Function definition with two parameters
void greet(string name, int age) {
    cout << "Hello, " << name << "! You are " << age << " years old." << endl;
}

int main() {
    greet("Alice", 30);  // Call the greet function with arguments
    return 0;
}

Explanation:

• Function: greet() takes two parameters: name (a string) and age (an integer). It prints a personalized greeting message using the provided arguments.
• Calling the Function: We call greet() in main() with the values "Alice" and 30. These are passed as arguments to the function.
• Expected Output: The function will output a greeting with the name and age provided.

Expected Output:

Hello, Alice! You are 30 years old.

Example 3: Function Inside Another Function (Nested Function Call)

Aim: Demonstrate how one function can call another function inside it (nested function calls).

Code:

#include <iostream>
using namespace std;

// Function to calculate the square of a number
int square(int x) {
    return x * x;  // Returns the square of x
}

// Function to calculate the sum of squares of two numbers
int sumOfSquares(int a, int b) {
    return square(a) + square(b);  // Calls square() inside to calculate the sum
}

int main() {
    int result = sumOfSquares(3, 4);  // Call sumOfSquares() with 3 and 4
    cout << "Sum of squares: " << result << endl;
    return 0;
}

Expected Output:

Sum of squares: 25

Explanation of Result: The program calculates the sum of squares: 3^2 + 4^2 = 9 + 16 = 25.

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