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Difference between Structure and Class in C++

In C++, the structure is the same as the class with some differences. Security is the most important thing for both structure and class. A structure is not safe because it could not hide its implementation details from the end-user, whereas a class is secure as it may hide its programming and design details. In this article, we are going to discuss the difference between a structure and class in C++. But before discussing the differences, we will know about the structure and class in C++.

What is the structure in C++?

A structure is a grouping of variables of various data types referenced by the same name. A structure declaration serves as a template for creating an instance of the structure.


The syntax of the structure is as follows:

The "struct" keyword indicates to the compiler that a structure has been declared. The "structurename" defines the name of the structure. Since the structure declaration is treated as a statement, so it is often ended by a semicolon.

What is Class in C++?

A class in C++ is similar to a C structure in that it consists of a list of data members and a set of operations performed on the class. In other words, a class is the building block of Object-Oriented programming. It is a user-defined object type with its own set of data members and member functions that can be accessed and used by creating a class instance. A C++ class is similar to an object's blueprint.


The structure and the class are syntactically similar. The syntax of class in C++ is as follows:

In this syntax, the class is a keyword to indicate the compiler that a class has been declared. OOP's main function is data hiding, which is achieved by having three access specifiers: "public", "private", and "safe". If no access specifier is specified in the class when declaring data members or member functions, they are all considered private by default.

The public access specifier allows others to access program functions or data. A member of that class may reach only the class's private members. During inheritance, the safe access specifier is used. If the access specifier is declared, it cannot be changed again in the program.

Main differences between the structure and class

Here, we are going to discuss the main differences between the structure and class. Some of them are as follows:

  • By default, all the members of the structure are public. In contrast, all members of the class are private.
  • The structure will automatically initialize its members. In contrast, constructors and destructors are used to initialize the class members.
  • When a structure is implemented, memory allocates on a stack. In contrast, memory is allocated on the heap in class.
  • Variables in a structure cannot be initialized during the declaration, but they can be done in a class.
  • There can be no null values in any structure member. On the other hand, the class variables may have null values.
  • A structure is a value type, while a class is a reference type.
  • Operators to work on the new data form can be described using a special method.

Head-to-head comparison between the structure and class

Here, we are going to discuss a head-to-head comparison between the structure and class. Some of them are as follows:

Features Structure Class
Definition A structure is a grouping of variables of various data types referenced by the same name. In C++, a class is defined as a collection of related variables and functions contained within a single structure.
Basic If no access specifier is specified, all members are set to 'public'. If no access specifier is defined, all members are set to 'private'.
struct structure_name{
type struct_member 1;
type struct_member 2;
type struct_member 3;
type struct_memberN;
class class_name{
data member;
member function;
Instance Structure instance is called the 'structure variable'. A class instance is called 'object'.
Inheritance It does not support inheritance. It supports inheritance.
Memory Allocated Memory is allocated on the stack. Memory is allocated on the heap.
Nature Value Type Reference Type
Purpose Grouping of data Data abstraction and further inheritance.
Usage It is used for smaller amounts of data. It is used for a huge amount of data.
Null values Not possible It may have null values.
Requires constructor and destructor It may have only parameterized constructor. It may have all the types of constructors and destructors.


The following are similarities between the structure and class:

  • Both class and structure may declare any of their members private.
  • Both class and structure support inheritance mechanisms.
  • Both class and structure are syntactically identical in C++.
  • A class's or structure's name may be used as a stand-alone type.


Structure in C has some limitations, such as the inability to hide data, the inability to treat 'struct' data as built-in types, and the lack of inheritance support. The C++ structure overcame these drawbacks.

The extended version of the structure in C++ is called a class. The programmer makes it easy to use the class to hold both the data and functions, whereas the structure only holds data.

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