In programming, we have 4 ways of defining a function and they are :-

1. Takes something and returns something.
2. Takes something and returns nothing.
3. Takes nothing and returns something.
4. Takes nothing and returns nothing.

A class in C++ can have all the 4 above mentioned types of member functions as per requirement.

Syntax :

// Function Declaration - takes nothing and returns nothing

void funtion1();

// Function Declaration - takes nothing and returns something

int funtion2();

// Function Declaration - takes something and returns nothing

void funtion3(int a, int b);

// Function Declaration - takes something and returns something

int funtion4(int a, int b);

---

Example :

// Simple Function Types Example Program in C++
// Function Example

#include <iostream>

using namespace std;

void funtion1(); // Function Declaration - takes nothing and returns nothing

int funtion2(); // Function Declaration - takes nothing and returns something

void funtion3(int a, int b);

int funtion4(int a, int b); // Function Declaration - takes something and return something

int main() {
    int x, y;

    cout 
            
Output :
            
Simple Function Types Example Program in C++
It's simple function definition
Return Value: 1000
Addition: 30
Addition: 300