C++ Programs: When do we pass arguments by reference or pointer?

In C++, there are multiple ways to pass arguments to functions, including passing by value, passing by reference, and passing by pointer. In this article, we will discuss when it is appropriate to pass arguments by reference or pointer.

Passing Arguments by Reference

Passing arguments by reference means that the address of the original variable is passed to the function. This allows the function to directly modify the original variable.

Syntax

void functionName(int &arg) {
    // code
}

Example

#include <iostream>
using namespace std;

void addOne(int &x) {
    x++;
}

int main() {
    int num = 5;
    addOne(num);
    cout << num << endl;
    return 0;
}

Output

6

Explanation

In the example above, we define a function called "addOne" that takes an integer reference as an argument. Inside the function, we increment the value of the argument directly, which modifies the value of the original variable.

Use

Passing arguments by reference is useful when we want to modify the value of the original variable inside the function.

Passing Arguments by Pointer

Passing arguments by pointer means that the memory address of the original variable is passed to the function through a pointer variable. This also allows the function to modify the original variable.

Syntax

void functionName(int *arg) {
    // code
}

Example

#include <iostream>
using namespace std;

void multiplyByTwo(int *x) {
    *x *= 2;
}

int main() {
    int num = 5;
    multiplyByTwo(&num);
    cout << num << endl;
    return 0;
}

Output

10

Explanation

In the example above, we define a function called "multiplyByTwo" that takes an integer pointer as an argument. Inside the function, we dereference the pointer and multiply the value stored at the memory address by two. This modifies the original variable.

Use

Passing arguments by pointer is useful when we want to modify the value of the original variable inside the function and we do not want to create a copy of the variable.

Important Points

• Passing arguments by reference or pointer allows the function to modify the original variable.
• Pass by reference is when the address of the original variable is passed to the function.
• Pass by pointer is when the memory address of the original variable is passed to the function through a pointer variable.
• Pass by pointer may be preferred when we do not want a copy of the original variable.

Summary

In conclusion, passing arguments by reference or pointer allows the function to modify the original variable. Pass by reference is when the address of the original variable is passed to the function, while pass by pointer is when the memory address of the original variable is passed to the function through a pointer variable. Choosing between these two methods depends on the specific use case, but pass by pointer may be preferred when we do not want to create a copy of the original variable.