What Is Call by Reference in Data Structure?


Scott Campbell

In the world of data structures, understanding various ways of passing arguments is essential. One such method is called “Call by Reference.” In this article, we will explore what Call by Reference means and how it affects our programs.

What is Call by Reference?

In programming languages, when we pass arguments to a function, we can pass them either by value or by reference. Call by Reference is a method of passing arguments where the memory address of the variable is passed to the function rather than the actual value.

How does Call by Reference work?

When using Call by Reference, any changes made to the parameter inside the function will affect the original variable outside the function. This means that modifications made within the function will persist even after returning from it.

  • Step 1: The memory address of a variable is passed as an argument to a function.
  • Step 2: The function receives this memory address and can access and modify the value stored in that memory location.
  • Step 3: Any changes made to the parameter inside the function will directly update the original variable.


Let’s take a look at an example to understand Call by Reference better:


// Function that swaps two numbers using Call by Reference

void swap(int& num1, int& num2) {
int temp = num1;
num1 = num2;
num2 = temp;

int main() {
int a = 10;
int b = 20;

swap(a, b);

cout << "After swapping: "; cout << "a = " << a << ", b = " << b; return 0; } ``` In this example, we have a function called `swap` that takes two integer variables (`num1` and `num2`) as references. Inside the function, the values of `num1` and `num2` are swapped using a temporary variable. In the `main` function, we declare two variables `a` and `b` with initial values. We then call the `swap` function with these variables as arguments. After returning from the function, we print the updated values of `a` and `b`. The output of this program will be: ``` After swapping: a = 20, b = 10 ``` As you can see, even though the swapping operation was performed inside a function, it affected the original variables in the main program due to Call by Reference. Advantages of Call by Reference:

  • Efficiency: Call by Reference avoids unnecessary memory allocation and copying of large data structures.
  • Modifying Original Values: It allows us to modify the original values of variables from within a function without needing to return them explicitly.

Disadvantages of Call by Reference:

  • Unintended Side Effects: If not used carefully, Call by Reference can lead to unintended modifications of variables outside the intended scope.
  • Lack of Clarity: The use of Call by Reference might make it less clear where and how variables are being modified in a program.

In Conclusion,

Call by Reference is an important concept in data structures and programming languages. By understanding how it works and when to use it, you can write more efficient and flexible code. Remember to use Call by Reference only when necessary and ensure that any modifications made inside functions align with your program’s requirements.

With this knowledge, you are now equipped to utilize Call by Reference effectively in your future programming endeavors!

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