What is the Difference Between Structure and Class in C++

The main difference between Structure and Class in C++ is that Structure is a value type data type while Class is a reference type data type.

Structure and class are two programming concepts in C++.  C++ is a high level, general-purpose programming language that is a superset of C language as it consists of many advanced features. There are mainly two types of data; they are the called value type and reference type. In value type, a value is assigned to a variable directly. In reference type data, a variable does not store the actual data. It stores a reference to that particular data.

Key Areas Covered

1. What is Structure in C+
     – Definition, Functionality
2. What is Class in C++
     – Definition, Functionality
3. What is the Difference Between Structure and Class in C++
     – Comparison of Key Differences

Key Terms

Structure, Class, C++

What is Structure in C++

A structure is a single variable that can hold multiple data types. In other words, it consists of variables of multiple data types. A single name is used to reference them all. Moreover, there should be a structure declaration so that the programmer can use it in the main method. In the main method, he can create an instance of the structure and use it to perform the required task. An example of a program with structure is as follows.

Figure 1: C++ program with structure

As shown in the above figure, there is a structure called Book. It contains three properties: title, author and pages. In the main method, there is a structure type variable as b. The “strcpy” function helps to copy strings to the title and author properties.  The programmer can access the properties of the structure using the access operator (.). Likewise, he can assign values to title, author and pages. Finally, the cout statements print them on the console.

What is Class in C++

One main advantage of C++ is that it supports OOP. In OOP, everything is an object. The programmer has to create a class to create objects. A class consists of attributes and methods. An attribute describes the properties while methods describe the behaviors. These attributes and methods of a class are called members of that class.

The members of the class can have access specifiers. There are mainly three access specifiers as public, private and protected. The public members are visible to all other classes. The private members are only accessible within the class while protected members are accessible within the package and its subclasses. An example program with a class is as follows.

Figure 2: C++ program with class

As shown in the above figure, there is a class called Book. It has three public properties; they are the title, author and pages. In the main method, Book b declares that b is of type Book. The programmer can assign values to title, author and pages using the access operator (.). Finally, the cout statements print these values on the console.

Difference Between Structure and Class in C++

Definition

A structure in C++ is a value data type that can hold related data that belongs to various data types whereas a class in C++ is a blueprint that defines data and methods to create objects. Thus, this is the fundamental difference between Structure and Class in C++.

Inheritance

Furthermore, inheritance is a major difference between Structure and Class in C++. A structure in C++ cannot inherit other classes or structures whereas a class in C++ can inherit other classes or structures.

Instance

An instance of a structure in C++ is a structure variable while an instance of a class in C++ is an object. Hence, this is another difference between Structure and Class in C++.

Keyword

Moreover, the keyword to define a structure is “struct” while the keyword to define a class is “class”.

Default Access Specifier

Also, default access specifier is another difference between Structure and Class in C++. In a structure, if there are no access specifiers declared, then the member or the properties are public. However, in a class, if there are no access specifiers declared, then the members are private.

Conclusion

A variable is a memory location that can hold a value. It is necessary to store multiple data types as a single unit. Two programming features that allow storing multiple data types as a single unit are structure and class. The main difference between Structure and Class in C++ is that the Structure is a value type data type while the Class is a reference type data type.

Reference:

1. Python Strings (With Examples), Available here.
2. “Introduction to Classes and Objects.” Types of Network Topology in Computer Networks | Studytonight, Available here.