Class vs. Structure

What's the Difference?

Class and structure are both programming constructs used in object-oriented programming languages like C++ and Java. They are used to define custom data types that can hold both data members and member functions. However, there are some key differences between the two. A class is a reference type and supports inheritance, polymorphism, and encapsulation. It can have access specifiers like public, private, and protected. On the other hand, a structure is a value type and does not support inheritance or polymorphism. It is typically used for simple data structures and does not have access specifiers. In general, classes are more versatile and commonly used for creating complex objects, while structures are used for lightweight data storage.


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DefinitionA blueprint for creating objects with similar properties and behaviors.A user-defined data type that combines different data types into a single unit.
InstantiationObjects are created from classes using the "new" keyword.Structures are created directly without using the "new" keyword.
InheritanceSupports single inheritance, where a class can inherit from only one base class.Does not support inheritance.
Access ModifiersPublic, private, protected, and internal access modifiers can be used.Access modifiers are not applicable to structures.
Default ConstructorA class can have a default constructor.A structure does not have a default constructor.
Memory AllocationObjects of a class are reference types and are allocated on the heap.Structures are value types and are allocated on the stack.
NullableClasses can be nullable.Structures can be made nullable using the "?" symbol.
UsageClasses are commonly used for creating objects, implementing inheritance, and encapsulating data and behavior.Structures are often used for lightweight data structures, representing simple entities, and improving performance.
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Further Detail


When it comes to object-oriented programming, two fundamental concepts that often come into play are classes and structures. Both classes and structures are used to define custom data types, encapsulate data, and provide methods for manipulating that data. However, there are some key differences between the two that developers need to understand in order to make informed decisions about which one to use in different scenarios. In this article, we will explore the attributes of classes and structures, highlighting their similarities and differences.

Definition and Purpose

A class is a blueprint for creating objects, which are instances of the class. It defines the properties and behaviors that objects of that class will have. Classes are used to model real-world entities or abstract concepts, and they provide a way to organize and structure code by grouping related data and functions together.

A structure, on the other hand, is a value type that can contain fields, properties, and methods. Like classes, structures can also be used to define custom data types. However, structures are typically used for smaller, lightweight objects that are not intended to be modified frequently. They are often used to represent simple data structures or immutable objects.

Memory Allocation

One of the key differences between classes and structures is how they are allocated and stored in memory. Objects created from classes are reference types, which means that when an object is assigned to a variable or passed as a method parameter, only a reference to the object is stored. The actual object is stored on the heap, and multiple variables can reference the same object.

On the other hand, objects created from structures are value types, which means that when a structure is assigned to a variable or passed as a method parameter, a copy of the entire structure is made. Each variable holds its own copy of the data, and modifying one variable does not affect the others. Structures are stored on the stack, which makes them more memory-efficient but also limits their size.

Inheritance and Polymorphism

Another important distinction between classes and structures is their support for inheritance and polymorphism. Inheritance is the ability to create a new class based on an existing class, inheriting its properties and behaviors. Polymorphism allows objects of different types to be treated as objects of a common base type.

Classes support both inheritance and polymorphism. A class can be derived from another class, inheriting its members and extending its functionality. This allows for code reuse and promotes a hierarchical organization of classes. Polymorphism is achieved through method overriding and interfaces, enabling objects of different derived classes to be treated as objects of the base class.

Structures, on the other hand, do not support inheritance. They cannot be derived from other structures or classes. Structures are standalone entities that cannot participate in an inheritance hierarchy. Additionally, structures do not support polymorphism since they cannot be used as base types for other types.

Performance and Efficiency

Due to their different memory allocation and storage mechanisms, classes and structures have different performance characteristics. Classes, being reference types, require additional memory and processing overhead to manage the references and handle garbage collection. This can result in slower performance and increased memory usage, especially when dealing with large objects or a large number of objects.

Structures, being value types, are generally more memory-efficient and have better performance characteristics. Since structures are stored on the stack and copied by value, they do not require the same level of memory management as classes. This makes structures a good choice for small, lightweight objects or when performance is a critical factor.

Usage Guidelines

When deciding whether to use a class or a structure, there are some general guidelines that can help in making the right choice:

  • Use a class when you need to represent complex objects with a large number of properties and behaviors.
  • Use a class when you need to support inheritance and polymorphism.
  • Use a class when you want to create objects that can be shared and accessed by multiple variables.
  • Use a structure when you need a lightweight object that is not intended to be modified frequently.
  • Use a structure when you want to minimize memory usage and improve performance.
  • Use a structure when you need to represent simple data structures or immutable objects.


In summary, classes and structures are both important concepts in object-oriented programming, but they have distinct attributes and use cases. Classes are reference types that support inheritance and polymorphism, making them suitable for complex objects and code reuse. Structures, on the other hand, are value types that are more memory-efficient and have better performance characteristics, making them suitable for lightweight objects and performance-critical scenarios. By understanding the differences between classes and structures, developers can make informed decisions and choose the right tool for the job.

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