difference-between-call-by-value-and-call-by-reference-in-c++

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In C++, passing arguments can be accomplished via call by value or call by reference, which are two distinct techniques. Understanding these methods is crucial for grasping how data is transmitted to functions and how alterations in variables are managed for C++ programs that are efficient, secure, and maintainable. This article will cover the definitions of call by value and call by reference, their mechanics, scenarios of application, strengths, weaknesses, and distinctions in C++.

Table of Contents:

What is Call by Value in C++?

Call by value in C++ refers to the technique of passing arguments to a function in the programming context. In this approach, a duplicate of the original value is sent to the function. Therefore, if modifications occur within the function, the initial variable will remain unaffected.

Syntax

The structure for call by value is as follows:

void func(int x); // No special symbol required

How Call by Value Operates in C++

When a variable is transmitted to a function via value, then

  • The variable’s value is duplicated.
  • The function operates on this duplicated value, not the original.
  • The initial value remains unchanged, despite any alterations made to the parameter within the function.

Example:

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var isMobile = window.innerWidth “);

editor71512.setValue(decodedContent); // Set the default text editor71512.clearSelection();

editor71512.setOptions({ maxLines: Infinity });

function decodeHTML71512(input) { var doc = new DOMParser().parseFromString(input, “text/html”); return doc.documentElement.textContent; }

// Function to copy code to clipboard function copyCodeToClipboard71512() { const code = editor71512.getValue(); // Get code from the editor navigator.clipboard.writeText(code).then(() => { jQuery(“.maineditor71512 .copymessage”).show(); setTimeout(function() { jQuery(“.maineditor71512 .copymessage”).hide(); }, 2000); }).catch(err => { console.error(“Error copying code: “, err); }); }

function runCode71512() {

var code = editor71512.getSession().getValue();

jQuery(“#runBtn71512 i.run-code”).show(); jQuery(“.output-tab”).click();

jQuery.ajax({ url: “https://intellipaat.com/blog/wp-admin/admin-ajax.php”, type: “post”, data: { language: “cpp”, code: code, cmd_line_args: “”, variablenames: “”, action:”compilerajax” }, success: function(response) { var myArray = response.split(“~”); var data = myArray[1];

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"+data+"");
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document.getElementById("copyBtn71512").addEventListener("click", copyCodeToClipboard71512);
document.getElementById("runBtn71512").addEventListener("click", runCode71512);
document.getElementById("closeoutputBtn71512").addEventListener("click", closeoutput71512);



Output:

``````html How Call by Value Functions in C++

The code illustrates how the value of num is transmitted by value to alter the function, meaning that the modifications made within the function do not influence the original variables. Therefore, num retains its value of 5 outside the function.

When to Employ Call by Value in C++

  • You may employ call by value when you wish to safeguard the original value from modifications.
  • This can be utilized when you only need to access or manipulate a copy of the value.
  • It is advisable to use call by value for smaller data types like int, char, and float as copying them is quick and cost-effective.
  • This approach should be utilized when you aim to guarantee data safety and separation within the function.

Benefits of Call by Value in C++

  • By using the call by value technique, the original variable remains intact since the function operates on a duplicate of the original variable.
  • It is straightforward and secure to implement.
  • It simplifies debugging and maintenance because the function does not alter external variables.
  • Call by value is appropriate for smaller data types such as int, char, or bool.
  • It renders the code more foreseeable since the behavior of the function is independent.

Drawbacks of Call by Value in C++

  • The original variable cannot be altered within the function.
  • Memory utilization is heightened because a duplicate of each argument is created for processing.
  • Performance can be lower when dealing with larger data types, such as arrays or structures.
  • It is inappropriate for situations requiring multiple return values.
  • Call by value can incur unnecessary overhead in some instances, even when duplication is not needed.

What is Call by Reference in C++?

Call by reference in C++ is a mechanism for passing arguments to a function where the actual memory address of the variable is conveyed. In this approach, if any modifications are made to the parameter directly, they will impact the original variable.

Syntax

The syntax for call by reference is:

void func(int &x); // Note the & symbol

How Call by Reference Functions in C++

When a variable is transmitted by reference in the program, then

  • No duplication of the original variable is created.
  • A reference to the original variable is utilized.
  • Modifying the parameter within the function will also change the original variable outside the function.

Example:

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Code Copied!

var isMobile = window.innerWidth “);

editor66054.setValue(decodedContent); editor66054.clearSelection();

editor66054.setOptions({ maxLines: Infinity });

function decodeHTML66054(input) { var doc = new DOMParser().parseFromString(input, “text/html”); return doc.documentElement.textContent; }

function copyCodeToClipboard66054() { const code = editor66054.getValue(); navigator.clipboard.writeText(code).then(() => { jQuery(“.maineditor66054 .copymessage”).show(); setTimeout(function() { jQuery(“.maineditor66054 .copymessage”).hide(); }, 2000); }).catch(err => { console.error(“Error copying code: “, err); }); }

function runCode66054() { var code = editor66054.getSession().getValue();

jQuery(“#runBtn66054 i.run-code”).show(); jQuery(“.output-tab”).click();

jQuery.ajax({ url: “https://intellipaat.com/blog/wp-admin/admin-ajax.php”, type: “post”, data: { language: “cpp”, code: code, cmd_line_args: “”, variablenames: “”, action: “compilerajax” }, success: function(response) { var myArray = response.split(“~”); var data = myArray[1];

jQuery(“.output66054”).html(“

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function closeoutput66054() { jQuery(“.maineditor66054 .code-editor-output”).hide(); }

// Attach event listeners to the buttons document.getElementById(“copyBtn66054”).addEventListener(“click”, copyCodeToClipboard66054); document.getElementById(“runBtn66054”).addEventListener(“click”, runCode66054); document.getElementById(“closeoutputBtn66054”).addEventListener(“click”, closeoutput66054);

Output:

How Call by Reference Functions in C++

The code demonstrates how num is transmitted by reference to the modify function, meaning any alterations made within the function will directly change the original variable. Thus, num will become 15 outside the function.

When to Utilize Call by Reference

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  • You may utilize the call by reference technique when there is a necessity to alter the original variable.
  • Employ this technique when transferring sizable data structures such as arrays, structs, or objects, which avoids the burden of duplication.
  • This approach should be applied when you wish to return several values from a function.
  • It is essential to use the call-by-reference technique, as it is required for optimal performance and efficacy.

Benefits of Call by Reference in C++

  • Modifications done within the function immediately influence the original variable.
  • It promotes efficient memory allocation since there is no requirement to duplicate the data, thus conserving memory.
  • The call by reference technique is beneficial when handling large data types for rapid processing.
  • It facilitates the return of multiple values.
  • It minimizes overhead and enhances speed and agility.

Drawbacks of Call by Reference in C++

  • Employing call by reference may sometimes result in bugs if unintended alterations occur.
  • It is relatively unsafe because it can impact the entire program if an error arises in another section.
  • Identifying and debugging issues is challenging.
  • Using call by reference necessitates the & symbol to pass a variable by reference.
  • It may introduce unnecessary complexity when applied to simple and small data types.

Distinctions Between Call by Value and Call by Reference in C++

Below are some principal distinctions between call by value and call by reference in C++.

1. Parameter Passing: Value vs. Reference

Call by value delivers a duplicate of the original variable for processing, whereas call by reference provides the address of the original variable for processing.

Example:

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var isMobile = window.innerWidth “);

editor13191.setValue(decodedContent); // Set the default text editor13191.clearSelection();

editor13191.setOptions({ maxLines: Infinity });

function decodeHTML13191(input) { var doc = new DOMParser().parseFromString(input, “text/html”); return doc.documentElement.textContent; }

// Function to copy code to clipboard function copyCodeToClipboard13191() { const code = editor13191.getValue(); // Get code from the editor navigator.clipboard.writeText(code).then(() => { jQuery(“.maineditor13191 .copymessage”).show(); setTimeout(function() { jQuery(“.maineditor13191 .copymessage”).hide(); }, 2000); }).catch(err => { console.error(“Error copying code: “, err); }); }

function runCode13191() { var code = editor13191.getSession().getValue();

jQuery(“#runBtn13191 i.run-code”).show(); jQuery(“.output-tab”).click(); jQuery.ajax({ url: “https://intellipaat.com/blog/wp-admin/admin-ajax.php”, type: “post”, data: { language: “cpp”, code: code, cmd_line_args: “”, variablenames: “”, action:”compilerajax” }, success: function(response) { var myArray = response.split(“~”); var data = myArray[1];

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function closeoutput13191() { var code = editor13191.getSession().getValue(); jQuery(“.maineditor13191 .code-editor-output”).hide(); }

// Attach event listeners to the buttons document.getElementById(“copyBtn13191”).addEventListener(“click”, copyCodeToClipboard13191); document.getElementById(“runBtn13191”).addEventListener(“click”, runCode13191); document.getElementById(“closeoutputBtn13191”).addEventListener(“click”, closeoutput13191);

Output:

1. What is Passed

The code illustrates that the variable “a” is sent to callByValue, a duplicate of “a” is forwarded, and the function operates on a distinct value, whereas the variable “b” is sent to callByReference, the actual address of “b” is sent, and the function operates on the original value, after which the values are displayed in the console.

2. How Call by Value & Reference Modify Variables

When utilizing the call by value technique, if alterations are made within the function, it will not influence the original variable, and the original value remains unchanged. Conversely, when employing the call by reference method, if alterations are made within the function, it will directly impact the original variable, resulting in a change to the original value.

Example:

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editor17709.setValue(decodedContent); // Set the default text editor17709.clearSelection();

editor17709.setOptions({ maxLines: Infinity });

function decodeHTML17709(input) { var doc = new DOMParser().parseFromString(input, “text/html”); return doc.documentElement.textContent; }

// Function to duplicate code to clipboard function copyCodeToClipboard17709() { const code = editor17709.getValue(); // Acquire code from the editor navigator.clipboard.writeText(code).then(() => { jQuery(“.maineditor17709 .copymessage”).show(); setTimeout(function() { jQuery(“.maineditor17709 .copymessage”).hide(); }, 2000); }).catch(err => { console.error(“Error duplicating code: “, err); }); }

function runCode17709() { var code = editor17709.getSession().getValue();

jQuery(“#runBtn17709 i.run-code”).show(); jQuery(“.output-tab”).click();

jQuery.ajax({ url: “https://intellipaat.com/blog/wp-admin/admin-ajax.php”, type: “post”, data: { language: “cpp”, code: code, cmd_line_args: “”, variablenames: “”, action: “compilerajax” }, success: function(response) { var myArray = response.split(“~”); var data = myArray[1];

jQuery(“.output17709”).html(“

" + data + "

“); jQuery(“.maineditor17709 .code-editor-output”).show(); jQuery(“#runBtn17709 i.run-code”).hide(); } }); }

function closeoutput17709() { var code = editor17709.getSession().getValue(); jQuery(“.maineditor17709 .code-editor-output”).hide(); }

// Attach event listeners to the buttons document.getElementById(“copyBtn17709”).addEventListener(“click”, copyCodeToClipboard17709); document.getElementById(“runBtn17709”).addEventListener(“click”, runCode17709); document.getElementById(“closeoutputBtn17709”).addEventListener(“click”, closeoutput17709);

Output:

2. Impact on Original Variable

The code illustrates how the variable ‘a’ is passed via call-by-value, leaving its original unchanged, while the variable ‘b’ is passed by reference, resulting in a change to its original value as the function operates directly on it, with the outcomes printed to the console.

3. Memory Efficiency: Call by Value vs. Reference

Call by value necessitates greater memory as it generates a copy of each variable given to the function, making it costly for large data types. Conversely, the call by reference technique consumes less memory since it does not create a duplicate.

Example:

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});

function decodeHTML55050(input) {
var doc = new DOMParser().parseFromString(input, “text/html”);
return doc.documentElement.textContent;
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// Function to duplicate code to clipboard
function copyCodeToClipboard55050() {
const code = editor55050.getValue(); // Retrieve code from the editor
navigator.clipboard.writeText(code).then(() => {
// alert(“Code duplicated to clipboard!”);

jQuery(“.maineditor55050 .copymessage”).show();
setTimeout(function() {
jQuery(“.maineditor55050 .copymessage”).hide();
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}).catch(err => {
console.error(“Error duplicating code: “, err);
});
}

function executeCode55050() {

var code = editor55050.getSession().getValue();

jQuery(“#runBtn55050 i.run-code”).show();
jQuery(“.output-tab”).click();

jQuery.ajax({
url: “https://intellipaat.com/blog/wp-admin/admin-ajax.php”,
type: “post”,

data: {
language: “cpp”,
code: code,
cmd_line_args: “”,
variablenames: “”,
action:”compilerajax”
},
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var myArray = response.split(“~”);
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function closeOutput55050() {
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jQuery(".maineditor55050 .code-editor-output").hide();
}

// Bind event handlers to the buttons
document.getElementById("copyBtn55050").addEventListener("click", copyCodeToClipboard55050);
document.getElementById("runBtn55050").addEventListener("click", executeCode55050);
document.getElementById("closeoutputBtn55050").addEventListener("click", closeOutput55050);

Example:

3. Memory Usage

The code illustrates how a fresh copy of a variable is generated when it is passed by value, with the function employing a distinct memory address; conversely, the same memory address is utilized by the function when the variable is passed by reference, thus eliminating additional memory usage.

4. Performance Assessment: Call by Value vs. Reference

The call by value technique exhibits slower performance when dealing with sizeable data types like arrays or structures, whereas the call by reference technique demonstrates enhanced performance for large data types as it circumvents the need for copying.

Example:

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function decodeHTML1525(input) { var doc = new DOMParser().parseFromString(input, "text/html"); return doc.documentElement.textContent; }

// Function to duplicate code to clipboard function copyCodeToClipboard1525() { const code = editor1525.getValue(); // Retrieve code from the editor navigator.clipboard.writeText(code).then(() => { // alert("Code duplicated to clipboard!");

jQuery(".maineditor1525 .copymessage").show(); setTimeout(function() { jQuery(".maineditor1525 .copymessage").hide(); }, 2000); }).catch(err => { console.error("Error duplicating code: ", err); }); }

function executeCode1525() {

var code = editor1525.getSession().getValue();

jQuery("#runBtn1525 i.run-code").show(); jQuery(".output-tab").click();

jQuery.ajax({ url: "https://intellipaat.com/blog/wp-admin/admin-ajax.php", type: "post",

data: { language: "cpp", code: code, cmd_line_args: "", variablenames: "", action:"compilerajax" }, success: function(response) { var myArray = response.split("~"); var data = myArray[1];

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Output:

4. Performance

The snippet demonstrates how the call by value approach produces a replica of the full vector, which utilizes more time and memory, whereas the call by reference technique interacts directly with the original vector, yielding significantly faster and more efficient results.

5. Safety Considerations: Which Method is More Secure?

Call by value is more secure than call by reference since alterations within the function do not influence the rest of the program, making it easier to manage bugs.

Illustration:

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editor8138.setValue(decodedContent); // Set the default text editor8138.clearSelection();

editor8138.setOptions({ maxLines: Infinity });

function decodeHTML8138(input) { var doc = new DOMParser().parseFromString(input, "text/html"); return doc.documentElement.textContent; }

// Function to copy code to clipboard function copyCodeToClipboard8138() { const code = editor8138.getValue(); // Get code from the editor navigator.clipboard.writeText(code).then(() => { // alert("Code copied to clipboard!");

jQuery(".maineditor8138 .copymessage").show(); setTimeout(function() { jQuery(".maineditor8138 .copymessage").hide(); }, 2000); }).catch(err => { console.error("Error copying code: ", err); }); }

function runCode8138() {

var code = editor8138.getSession().getValue();

jQuery("#runBtn8138 i.run-code").show(); jQuery(".output-tab").click();

jQuery.ajax({ url: "https://intellipaat.com/blog/wp-admin/admin-ajax.php", type: "post",

data: { language: "cpp", code: code, cmd_line_args: "", variablenames: "", action:"compilerajax" }, success: function(response) { var myArray = response.split("~"); var data = myArray[1];

jQuery(".output8138").html("

"+data+"");
									jQuery(".maineditor8138 .code-editor-output").show();
									jQuery("#runBtn8138 i.run-code").hide();

} })

}

function closeoutput8138() { var code = editor8138.getSession().getValue(); jQuery(".maineditor8138 .code-editor-output").hide(); }

// Attach event listeners to the buttons document.getElementById("copyBtn8138").addEventListener("click", copyCodeToClipboard8138); document.getElementById("runBtn8138").addEventListener("click", runCode8138); document.getElementById("closeoutputBtn8138").addEventListener("click", closeoutput8138);

Output:

5. Safety

This code illustrates that the variable passed through the call by value mechanism remains unaltered and does not impact the overall program, whereas the call by reference modifies the value of variable b; hence, call by value is considered more secure than the call by reference method.

6. Appropriate Data Types for Value vs. Reference

Call by value is ideal for smaller data types such as int and char, where cloning the variables is more affordable and simpler. On the other hand, call by reference is preferable for larger data types like arrays, in order to prevent the overhead associated with copying.

Illustration:

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editor25810.setValue(decodedContent); // Set the default text editor25810.clearSelection();

editor25810.setOptions({ maxLines: Infinity });

function decodeHTML25810(input) { var doc = new DOMParser().parseFromString(input, "text/html"); return doc.documentElement.textContent; }

// Function to copy code to clipboard function copyCodeToClipboard25810() { const code = editor25810.getValue(); // Retrieve code from the editor navigator.clipboard.writeText(code).then(() => { // alert("Code copied to clipboard!"); jQuery(".maineditor25810 .copymessage").show(); setTimeout(function() { jQuery(".maineditor25810 .copymessage").hide(); }, 2000); }).catch(err => { console.error("Error copying code: ", err); }); }

function runCode25810() { var code = editor25810.getSession().getValue();

jQuery("#runBtn25810 i.run-code").show(); jQuery(".output-tab").click();

jQuery.ajax({ url: "https://intellipaat.com/blog/wp-admin/admin-ajax.php", type: "post", data: { language: "cpp", code: code, cmd_line_args: "", variablenames: "", action:"compilerajax" }, success: function(response) { var myArray = response.split("~"); var data = myArray[1];

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function closeoutput25810() { var code = editor25810.getSession().getValue(); jQuery(".maineditor25810 .code-editor-output").hide(); }

// Attach event listeners to the buttons document.getElementById("copyBtn25810").addEventListener("click", copyCodeToClipboard25810); document.getElementById("runBtn25810").addEventListener("click", runCode25810); document.getElementById("closeoutputBtn25810").addEventListener("click", closeoutput25810);

Output:

Data Type for Value vs. Reference

The code illustrates that using the call by value method is suitable for small data types like int, as it easily modifies the value, while the call by reference method is optimal for larger data types such as arrays since it readily updates the array, with the results printed to the console.

Here is a table for better clarity regarding the distinctions between call by value and call by reference.

Feature Call by Value Call by Reference
What is Passed Passes a duplicate of the variable to the function Passes the address/reference of the variable
Impact on Original Variable The original variable remains unaffected The original variable can be altered
Memory Usage More memory (due to duplication) Less memory (no duplication)
Efficiency Slower for larger data types Faster for larger data types
Security Safer (no unintentional modification) Less secure than call by value (can change the original data)
Data Type Suitability Small data types (int, char) where duplication is inexpensive Large data types (arrays, objects) to prevent duplication overhead
Syntax void func(int x) void func(int &x)

Conclusion

In C++, grasping the difference between call by value and call by reference methods for parameter passing is essential for crafting efficient and secure programs. The call by value method is applied when protecting the original data is critical, creating a copy inside the function, while the call by reference method is beneficial when altering the original variable and avoiding the overhead of duplicating large data types. Thus, selecting the appropriate method aids in optimizing performance, memory usage, and code safety.

Difference Between Call by Value and Call by Reference in C++ – FAQs

Q1. What is call by value in C++?

Call by value in C++ is a technique for passing arguments to a function within the program. In this technique, a duplicate of the original value is given to the function.

Q2. What is call by reference in C++?

Call by reference in C++ is a method of passing arguments to a function where the actual memory address of the variable is provided.

Q3. Which method is more secure?

Call by value is more secure as it does not permit the function to alter the original data.

Q4. When should I utilize call by reference?

You should adopt call by reference when you intend to modify...

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the initial variable, or when dealing with sizable objects, to evade duplication.

Q5. Does call by reference require additional memory?

No, call by reference usually consumes less memory since it prevents the creation of duplicates for large variables.

The article Difference Between Call by Value and Call by Reference in C++ first appeared on Intellipaat Blog.

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