Data Hiding in C++: Everything You Need to Know

What Does Data Hiding Mean?

Data hiding is an object-oriented programming (OOP) technique specifically used to hide internal object details (i.e., data members). Data hiding guarantees exclusive data access to class members only and protects and maintains object integrity by preventing intended or unintended changes and intrusions.

Classes are groups of objects that share common properties or behaviors. For instance, a specific housecat is an object in the class of “cats.” The world’s cats share some characteristics from the same template (e.g., they have whiskers and tails, and they are felines). Carrying this idea over to Java, the “cat” class is a blueprint we can use to generate any individual cats that include all cat characteristics (e.g., eye shape, tail length, fur color). However, you couldn't create a running shoe from the "cat" class because the latter lacks the characteristics needed to create a shoe.

Programs incorporating data hiding are segregated into objects with specific data and functions. This programming technique improves the programmer’s ability to create classes with unique functions and data sets, which avoids unnecessary penetration from other program classes.

Data hiding also diminishes system complexity for increased robustness by reducing or limiting interdependencies between software components.

Data hiding is alternately called information hiding.

The general concept of data hiding is typically associated with two other techniques:

• Abstraction
• Encapsulation

We will explore those techniques later.

So, to recap, data hiding in C++ hides the data from components of the program that don't have to be retrieved. The process ensures exclusive data access to class members while providing object integrity by preventing the data from being changed accidentally or deliberately.

Here is an example of data hiding in C++:

1. #include<iostream>  
2. using namespace std;  
3. class Base{  
4.        
5.     int num;  //by default private  
6.     public:  
7.        
8.     void getData();  
9.     void showData();  
10.        
11. };  
12. void Base :: getData()  
13. {  
14.     cout<< "Enter any Integer value" <<endl;   
15.     cin>>num;  
16.        
17. }  
18. void Base :: showData()  
19. {  
20.     cout<< "The value is " << num <<endl;  
21. }  
22.     
23. int main(){  
24.     Base obj;       
25.     obj.getData();  
26.     obj.showData();   
27.     return 0;  
28. }  

Output

Enter any Integer value

2

The value is 2

Source

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Access Specifiers

Data hiding involves classes, and classes have three different kinds of protection/access specifiers Typically, the data within a class is private, and the functions are public. Since the data is hidden, it will be safe from accidental manipulation.

Private Members/Methods

These can only be accessed by methods defined as part of the class. Data is typically defined as private to stop direct outside access from other classes. However, private members can be accessed by class members.

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Public Members/Methods 

These can be accessed from anywhere in the program. In this case, class methods are usually public and used to manipulate data residing in the class. As a rule, data shouldn't be declared public. However, members and objects of the class can access public members.

Protected Member/Methods

These are private within a class They are available for private access only in the derived class.

Data Abstraction 

Data encapsulation is collecting data, and its related functions into a single unit called a class. In plainer language, you can conceal sensitive information and limit access to an object's internal state if you use an invisible attribute outside the object and bundle it with methods that enable read or write access.

That’s the difference between external and internal implementation. Data abstraction protects class implementation from unintentional error and lets it develop in response to elements like bug reports or changing requirements without requiring user action.

So, put simply, data abstraction hides unnecessary details and exposes only the needed details. It’s like a “need to know” basis.

Here is an example of data abstraction code:

// program to calculate the power of a number.

1. #include <iostream>  
2. #include<math.h>  
3. using namespace std;  
4. int main()  
5. {    
6.  int n = 4;  
7.    int power = 3;  
8.    int result = pow(n,power);         // pow(n,power) is the  power function  
9.    std::cout << "Cube of n is : " <<result<< std::endl;  
10.    return 0;  
11. }  

Output:

Cube of n is : 64

Source

Data Encapsulation

Data encapsulation is the technique of collecting data and its related functions into a single unit called a class. In plainer language, you can conceal sensitive information and limit access to an object’s internal state if you use an invisible attribute located outside of the object and bundle it with methods that enable read or write access.

So, it's up to you to decide if an attribute can be updated or read, read-only, or even not visible, depending on your chosen methods.

Here’s an example of encapsulation, courtesy of Javamadesoeasy:

class Employee{

   private String id; //private field

   public String getId() { //private field accessed inside public method

          return id;

   }

   public void setId(String id) {

          this.id = id;

   }

}

/** JavaMadeSoEasy.com */

public class EncapsulationTest {

   public static void main(String[] args) {

          Employee emp=new Employee();

          emp.setId("1"); //public method can be accessed outside class.

          System.out.println("emp.getId()  >  "+emp.getId());

   }

}

/* OUTPUT

emp.getId()  >  1

*/

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What’s the Difference Between Data Hiding and Data Encapsulation?

Since both data protection concepts work together for a common purpose, namely the auxiliary gatekeepers of sensitive information, the terms are frequently used interchangeably in object-oriented programming. However, though the data encapsulation and concealing functions are alike, they operate at different levels, so they're physically distinct.

Here are five fundamental differences between data hiding and data encapsulation:

• The main difference between data hiding in C++ and encapsulation is that data hiding focuses on improving data security within the program, while encapsulation deals with hiding the program’s complexity.
• Hidden data must be designated as private only. The data in data encapsulation can be public or private.
• Data encapsulation focuses on wrapping (i.e., encapsulating) complex data to offer a simplified perspective to the users, while data hiding focuses on restricting a program’s data use to ensure data security.
• Data encapsulation targets how the data is accessed and how different objects behave. Data hiding focuses on object member accessibility within a class, and information hiding is the most common encapsulation method. The programmer conceals the object member's structure and its implementation methods.
• Data encapsulation is defined as a sub-process of data hiding, and data hiding is both a process and an overall strategy. So, all data encapsulation is considered data hiding, but not all data hiding is considered data encapsulation.

Applications of Data Hiding in C++

Data hiding can be applied to any situation that involves private, sensitive, or confidential data. These include:

• Academic records and grade transcripts
• Bank account numbers and balances
• Medical records
• Corporate financial data

Benefits of Data Hiding in C++

Although we have alluded to the benefits of data hiding, let’s openly list its advantages:

• Data hiding minimizes data complexity and unpredictability
• Data hiding increases the program’s reusability
• It reduces system complexity while increasing the system’s robustness by minimizing interdependencies between its software components
• It conceals the data’s physical hoarding architecture, which aids in clearly defining the interface, as it improves reading and comprehension
• Data hiding protects data from unauthorized access and data corruption. To put it simpler, data hiding helps conceal sensitive information, ensuring enhanced security measures against intruders and hackers. For example, if a company’s internal data were made public, hackers could easily access it and make destructive changes to the program’s functionality. But hackers can’t access what they can’t see. So the concealed data appear invisible to anyone outside the class, and, as a result, hiding the data makes it considerably more difficult for a hacker to crack the code.
• The encapsulated classes are simple, easily manageable, and make it easier to develop future applications

Disadvantages of Data Hiding in C++

There’s only one disadvantage to the process of data hiding. It requires extra coding, so programmers must write more extended codes. However, considering the weight of all its benefits, it’s a small price to pay in the long run.

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