Discuss the differences between pass-by-value and pass-by-reference in C++ and provide examples to illustrate their usage.

In C++, there are two ways to pass arguments to functions: pass-by-value and pass-by-reference. These methods have distinct differences in how they handle memory and modify the original data. Let's delve into each approach and provide examples to highlight their usage and effects.

1. Pass-by-Value:
When passing arguments by value, a copy of the value is made and passed to the function. This means that any modifications made to the parameter within the function do not affect the original argument outside of the function's scope. Here are some key points regarding pass-by-value:

* The function operates on a local copy of the value, keeping the original data intact.
* Changes made to the parameter within the function are not reflected in the caller's scope.
* Memory consumption may increase when large objects are passed, as a copy of the data is created.Example:

```
cpp`void increment(int value) {
value++; // Modifying the local copy
std::cout << "Inside function: " << value << std::endl;
}

int main() {
int num = 5;
increment(num); // Pass-by-value
std::cout << "Outside function: " << num << std::endl;
return 0;
}`
```
Output:

```
bash`Inside function: 6
Outside function: 5`
```
In the example, the `increment()` function receives a copy of `num` as `value`. Modifying `value` inside the function does not affect the original `num` variable in the `main()` function.
2. Pass-by-Reference:
When passing arguments by reference, a reference to the original data is passed to the function. This allows direct access to the original data, enabling modifications that persist outside the function's scope. Here are some key points regarding pass-by-reference:

* The function operates directly on the original data, allowing modifications to affect the caller's scope.
* Memory consumption remains the same, as no additional copy is created.
* Changes made to the reference within the function will affect the original data.Example:

```
cpp`void increment(int& value) {
value++; // Modifying the original data through reference
std::cout << "Inside function: " << value << std::endl;
}

int main() {
int num = 5;
increment(num); // Pass-by-reference
std::cout << "Outside function: " << num << std::endl;
return 0;
}`
```
Output:

```
bash`Inside function: 6
Outside function: 6`
```
In this example, the `increment()` function receives `num` as a reference through `int& value`. Any modifications made to `value` directly affect the original `num` variable in the `main()` function.

Pass-by-value is useful when you want to preserve the original data and prevent unintended modifications. It also provides a clear separation between the caller and the function, ensuring encapsulation. On the other hand, pass-by-reference is efficient when working with large data structures and allows modifications to propagate to the caller, eliminating the need for returning values.

It's important to note that pass-by-reference in C++ can also be achieved through pointers (`int* value`) and references (`int& value`). Pointers require explicit dereferencing, while references provide a more intuitive syntax. Both methods enable modifications to the original data within the function.