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Call by Value vs. Call by Reference: What's the Difference?

Edited by Aimie Carlson || By Janet White || Published on February 5, 2024
Call by value copies the actual value of an argument into the formal parameter of the function, whereas call by reference passes the argument's address, allowing direct modification of the original variable.

Key Differences

Call by value in programming means that when a function is called, the values of the actual parameters are copied into the function's formal parameters. In call by reference, instead of values, the addresses of the actual parameters are passed, linking the formal and actual parameters.
With call by value, modifications made to the formal parameters in the function do not affect the actual parameters. In contrast, call by reference allows the function to modify the actual parameters since the formal parameters reference the actual memory locations.
Call by value is generally safer as it protects the actual parameters from unintended changes. Call by reference, being more memory-efficient, can lead to unintentional side effects if the function alters the value of the referenced variable.
In languages that support both methods, call by value is typically used when the integrity of the original data is paramount. Call by reference is preferred for large data structures or objects where copying values would be inefficient.
Call by value results in additional memory usage due to duplication of values, which can be a drawback for large data. Call by reference, while conserving memory, requires careful handling to prevent errors due to the direct manipulation of variables.

Comparison Chart

Parameter Passing

Copies actual value
Passes address of the variable

Memory Usage

More, due to duplication
Less, no duplication

Effect on Original Variable

No change to the original variable
Can modify the original variable


Safer, no unintended side effects
Risk of side effects

Use Case

Used when data integrity is important
Used for efficiency with large data structures

Call by Value and Call by Reference Definitions

Call by Value

Uses more memory due to value duplication.
Call by value is less memory efficient due to creating copies of arguments.

Call by Reference

Passes the address of an argument to a function.
With call by reference, changes in the function affect the original variable.

Call by Value

Protects the original data from modification.
Call by value is used to ensure the actual argument remains unchanged.

Call by Reference

Can lead to unintended side effects.
Care must be taken with call by reference to prevent accidental data modification.

Call by Value

Copies the value of an argument into a function.
In call by value, modifying a parameter inside the function doesn’t alter the original argument.

Call by Reference

Function can modify the original data.
Call by reference allows the function to directly update the argument's value.

Call by Value

Function works with a copy of the argument.
Using call by value, the function's actions remain local to that function only.

Call by Reference

More memory efficient, avoids duplication.
Using call by reference is preferred for large objects due to its memory efficiency.

Call by Value

Safe method preventing side effects.
Call by value is chosen to avoid unintended changes to variables.

Call by Reference

Suitable for large data structures.
Call by reference is used for efficient processing of large arrays.

Call by Value

(programming) An evaluation strategy in which the arguments to a function are evaluated first, and the result is passed into the function.

Call by Reference

(programming) An evaluation strategy in which the arguments to a function are evaluated first, and a pointer to the result is passed to the function.


Can call by reference modify the original data?

Yes, it directly modifies the original variable.

What is call by value in programming?

A method where the actual value of an argument is passed to a function.

What does call by reference mean?

Passing the address of an argument to a function, allowing direct modification.

How does call by value affect the original variable?

It does not affect the original variable; changes are made to the copy.

When should call by value be used?

When data integrity and protection from modification are important.

What type of data is best suited for call by reference?

Large data structures like arrays or objects.

Is call by value safer than call by reference?

Yes, because it doesn't risk altering the original data.

Why is call by reference more memory efficient?

It avoids duplicating large data structures by passing addresses.

Does call by value have a performance impact?

It can, especially with large data due to copying overhead.

Does call by value work well with small data types?

Yes, as the overhead of copying small data is negligible.

Can call by value be used for efficiency?

Not typically, as it involves additional memory use for copying.

What is a common use of call by reference?

Efficiently passing and modifying large data structures.

Can functions using call by reference create side effects?

Yes, due to the direct manipulation of variables.

Are primitive data types typically passed by value?

Yes, primitives are often passed by value in many programming languages.

Is call by reference available in all programming languages?

No, some languages only support call by value.

How do you implement call by reference?

By passing pointers or references to variables.

Is the original variable accessible in call by value?

No, only its copy is accessible within the function.

How does call by reference affect function arguments?

Arguments can be changed within the function, reflecting in the original.

Can call by value and call by reference be mixed?

Yes, depending on the language and function design.

Why might call by reference be risky?

Because it can unintentionally alter the state of variables.
About Author
Written by
Janet White
Janet White has been an esteemed writer and blogger for Difference Wiki. Holding a Master's degree in Science and Medical Journalism from the prestigious Boston University, she has consistently demonstrated her expertise and passion for her field. When she's not immersed in her work, Janet relishes her time exercising, delving into a good book, and cherishing moments with friends and family.
Edited by
Aimie Carlson
Aimie Carlson, holding a master's degree in English literature, is a fervent English language enthusiast. She lends her writing talents to Difference Wiki, a prominent website that specializes in comparisons, offering readers insightful analyses that both captivate and inform.

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