Difference between Call by Value and Call by Reference in Programming

Key Difference: Call by value and call by reference are both methods of passing arguments. In call by value, a copy of actual arguments is passed to respective formal arguments; whereas in call by reference the location or address of the actual arguments is passed to the formal arguments.

Call by Value and Call by Reference are two different functions that are primarily utilized in C programing languages. The C programing languages include C, which has often been called one of the most important programming languages out there. The reason for this is that C forms the basis of so many other programming languages out there, including C++ and C #, as well as Java, JavaScript, Perl, PHP, and Python, among so many others.

Call by value and call by reference are both methods of passing arguments. They can be used to pass value or data to another function. However, the manner in which they pass the arguments differ.

The primary difference between the two is that in call by value, a copy of actual arguments is passed to respective formal arguments; whereas in call by reference the location or address of the actual arguments is passed to the formal arguments. Due to this, any changes made in the formal arguments will also reflect in the actual arguments. Hence, care should be taken when using call by reference as it is very easy to accidently make changes in the formal arguments.

Call by Value is generally used as the default function in most C programming languages, especially such as C++, PHP, Visual Basic .NET, C# and REALbasic. However, most of them support Call by Reference by offering special syntax for call-by-reference parameters. Still, in C all the function arguments are passed by value, as C does not support references as the other languages do. The reason for this is the fact that in C the calling and the called functions do not share any memory. As they each have their own copy, the called function cannot directly alter a variable in the calling function. It can only alter its own personal copy. So, the call by reference would be pointless here.

Comparison between Call by Value and Call by Reference in Programming:

 

Call by Value

Call by Reference

Description

A function to pass data or value to other functions

A function to pass data or value to other functions

Languages used

C based programming languages

C based programming languages such as C++, Java, but not C itself

Purpose

To pass arguments to another function

To pass arguments to another function

Arguments

A copy of actual arguments is passed to respective formal arguments

Reference the location or address of the actual arguments is passed to the formal arguments

Changes

Changes are made in the own personal copy. Changes made inside the function are not reflected on other functions

Any changes made in the formal arguments will also reflect in the actual arguments. Changes made inside the function are reflected outside the function as well.

Value modification

Original value is not modified.

Original value is modified.

Memory Location

Actual and formal arguments will be created in different memory location

Actual and formal arguments will be created in same memory location

Safety

Actual arguments remain safe, they cannot be modified accidentally.

Actual arguments are not safe. They can be accidentally modified. Hence care is required when handling arguments.

Default

Default in most programming languages such as C++, PHP, Visual Basic .NET, C# and REALbasic

Supported by most programming languages, but not as default.

Reference: Wikipedia, Tutorials Point (Call by Value and Call by Reference),
Java T Point, CS Fundamentals
Image Courtesy: sitesbay.com, penjee.com

 

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