Difference Between Call by Value and Call by Reference
Have you ever wondered how a function in your code affects the variables you pass to it? The difference between Call by Value and Call by Reference is a fundamental concept that determines whether a function modifies your original data or just works with a copy of it. Let us read more about it!
Call by Value and Call by Reference are two methods of passing arguments to functions in programming. In this blog, we will understand the difference between call by value and call by reference in detail.
Table of Content
- Difference Between Call by Value and Call by Reference
- What is Call by Value?
- What is Call by Reference?
- Similarities Between Call by Value and Call by Reference
Best-suited Programming courses for you
Learn Programming with these high-rated online courses
Difference Between Call by Value and Call by Reference
Below is a table showing the difference between call by value and call by reference.
| Aspect |
Call by Value |
Call by Reference |
| Naming Convention |
Named so because it involves passing the actual values of arguments to the function. |
Named so because it involves passing the reference (address) of arguments to the function. |
| Effects of Changes |
Changes in the function to the parameters do not affect the original arguments. |
Changes in the function to the parameters directly affect the original arguments, as they are references. |
| Type of Passing |
Passes a copy of the variable's value. |
Passes the variable itself, meaning the address of the variable is passed. |
| Memory Location |
Uses different memory locations for actual arguments and parameters (formal and actual arguments are created in different memory locations). |
Uses the same memory location for actual arguments and parameters (formal and actual arguments are created in the same memory location). |
| Language Support |
Supported by languages like C++, C#, PHP, Visual Basic NET, etc., often as the default method. |
Supported by C++ (with references). Java uses a Call by Value approach where object references are passed by value, not the objects themselves. |
| Value Modification |
No modification in the original value. |
Modification occurs in the original value. |
| Internal Implementation |
Involves copying the value of the parameter to the function's local argument. |
Involves copying the address of the parameter to the function's local argument, leading to shared memory location. |
| Method of Passing |
Uses a straightforward method or simple technique for passing values. |
Requires defining pointer variables (or equivalent) to store the address of variables. |
| Manipulation of Variables |
Changes to dummy variables in the function do not affect the actual variables in the calling function, preventing manipulation of actual variables through function calls. |
Allows for direct manipulation of actual variables through function calls, as both refer to the same memory location. |
What is Call by Value?
Call by Value is a method of passing arguments to a function where the actual value of the argument is copied into a separate location accessible by the function. When the function operates on these arguments, it does so on their copies, so any changes made within the function do not affect the original arguments outside the function. This is a standard approach in many programming languages, especially for primitive data types like integers, floats, and characters.
Mind Map for Call by Value
Let's see an example in C programming language below to understand the concept better.
#include <stdio.h>
// Function to add 10 to the given numbervoid addTen(int number) { number = number + 10; printf("Inside function: %d\n", number);}
int main() { int originalNumber = 5;
// Function call does not change the originalNumber addTen(originalNumber); printf("Outside function: %d\n", originalNumber); return 0;}
Output
Inside function: 15
Outside function: 5
In the example above,
- The main function defines a variable originalNumber with the value 5.
- It then calls the addTen function, passing originalNumber as an argument.
- Inside the addTen function, the parameter number is a copy of originalNumber. Any operation inside addTen is performed on this copy. Here, it adds 10 to number and prints the result.
- However, once the control returns to main, originalNumber remains unchanged, as demonstrated by the final print statement.
In Call by Value, the function addTen does not have access to the actual variable originalNumber. It only works with a copy, so the original variable remains unaffected by whatever happens inside the function. This makes Call by Value a safer method when you want to ensure that the original values of variables are not altered.
What is Call by Reference?
Call by Reference is a method of passing arguments to a function where instead of passing the values of the variables, the function receives references to the actual variables. This means that the function operates directly on the original variables, and any changes made within the function are reflected in those variables outside the function. This method is commonly used in languages like C++, where you can pass references or pointers to achieve this effect.
Mind Map for Call by Reference
Let's see an example in C++ below to understand the concept better.
#include <iostream> using namespace std;
// Function declaration with a reference parametervoid addTen(int &number) { // Modify the parameter, which affects the original variable number = number + 10; cout << "Inside function: " << number << endl;}
int main() { // Initialize an integer variable int originalNumber = 5;
// Call the function with a reference to the variable addTen(originalNumber);
// Print the value after the function call to show that it has been changed cout << "Outside function: " << originalNumber << endl;
return 0;}
Output
Inside function: 15
Outside function: 15
In the example above,
- The addTen function takes an integer reference (int &number) as its parameter.
- When addTen is called in the main function, it is passed the reference to originalNumber.
- Inside addTen, any modification to number directly affects originalNumber because number is a reference to originalNumber.
- After the function call, originalNumber reflects the changes made inside addTen.
This demonstrates how Call by Reference allows a function to modify the original variables passed to it, in clear contrast to Call by Value where such modifications are not possible.
Similarities Between Call by Value and Call by Reference
Below is a Table highlighting the key similarities between call by value and call by reference.
| Aspect |
Call by Value and Call by Reference |
| Function Call |
Both methods are used when calling a function, though they differ in what is passed (value or reference). |
| Purpose |
Both are intended to supply data from the calling environment to a function for processing, enhancing modularity and reusability in programming. |
Thus, the concepts of Call by Value and Call by Reference are fundamental in understanding how functions interact with arguments in programming. While they share the common purpose of passing data to functions and supporting modularity in code design but they differ significantly in their implementation and effects.
FAQs
What is the main difference between Call by Value and Call by Reference?
Call by Value means that a copy of the actual value is passed to the function, so modifications made to the parameter inside the function do not reflect outside of it. Call by Reference, on the other hand, means a reference (or pointer) to the actual parameter is passed, so changes made inside the function do affect the original argument.
Does Call by Value provide more security compared to Call by Reference?
Yes, Call by Value is generally more secure as it passes a copy of the data, ensuring that the original data cannot be accidentally modified or corrupted. In contrast, Call by Reference can lead to unintended side effects on the original data.
Which is faster, Call by Value or Call by Reference?
Call by Reference is usually faster for large data structures or objects, as it avoids the overhead of copying large amounts of data. However, for small or primitive data types, Call by Value can be equally efficient or sometimes faster due to the overhead of accessing memory locations in Call by Reference.
Are there any specific use cases where one method is preferred over the other?
Call by Value is preferred when the integrity of the original data must be maintained without any risk of modification. Call by Reference is more useful when working with large data structures where performance is a concern, or when the function needs to modify the original data.
How do different programming languages implement these concepts?
Languages like C and C++ offer both Call by Value and Call by Reference (though in C, Call by Reference is simulated using pointers). Languages like Java use Call by Value for primitives and Call by Reference for objects. In contrast, Python and JavaScript use a model called Call by Sharing, which is often confused with Call by Reference.
Hello, world! I'm Esha Gupta, your go-to Technical Content Developer focusing on Java, Data Structures and Algorithms, and Front End Development. Alongside these specialities, I have a zest for immersing myself in v... Read Full Bio
Top Picks & New Arrivals
