Difference between Class and Struct (2023)

Difference between Class and Struct (1)

Before we understand the difference between Class and Struct, we should know a few basic concepts associated with them. Without an understanding of concepts, it is difficult to comprehend the differences between the two.

What Is Class and Object:

These are the two important concepts related to Object Oriented Programming, and they form the basis for framing the functions and data passing to other functions. For a better understanding, we can correlate it to a real-life example. A Class can be considered as a store, and an Object can be any of the individual, specific stores such as grocery, stationery, fruit, etc. All objects share the common properties of the main class – the store –, and in turn, the objects may have their own exclusive properties such as a specific design, lighting, etc. Through the objects, we can actually use the class; they form the instances of a class.

Syntax of a Class

Class Store {

public string things;

public string design;

}

(Video) CLASSES vs STRUCTS in C++

Syntax of an Object

Store grocery = new Store();

Store Stationery = new Store();

What Is a Struct?

A Struct includes only the data, and therefore it is helpful in framing the individual data requirements through the Struct objects. Unlike a class, it lacks functions. Here is its syntax:

struct grocery_entrance{

char entrance_name[50];

int entrance_size;

} grocery_entrance;

(Video) What Is The Difference Between struct And class In C++?

All stores can use the Struct ‘entrance’ with individual names and sizes.

What Is Inheritance?

It is similar to how a son inherits the possessions of his father and, in turn, the son can also add some other possessions of his own. The Class can be either a base class or a derived class, in which the former can be taken as the base to form the latter. The derived class adds few other properties for itself apart from what it gets from the base class. When we consider the above example, the grocery store can still be derived to a specific grocery store, such as XYZ grocery store.

Now that we are familiar with the basic concepts, we can go into the actual difference between Class and Struct.

How Do They Differ?

  • Re-usability: As Classes form the basic framework, they can be re-used; Structs, however, are individual elements with specific properties, so they cannot be re-used. For example, the grocery store Class can be used for any type of grocery store, but the Struct grocery_entrance is specific for that alone and there is no point in re-using it in other classes.
  • Visibility: All the functions in a Class are publicly available to its Objects. For example, we have a function named ‘things’ under the Class ‘store’. The function ‘things’ is visible to all its Objects, such as ‘grocery store, ‘stationery store’, etc. Such visibility is not possible with Structs as struct’s data is restricted to itself and not visible to other Structs. To make things clear, we can say that the data of ‘grocery_entrance’ is not publically visible to all other stores.
  • Pass by Reference & Pass by Value: Pass by Reference is sending only the memory location and not the actual data to the functions. This means that whenever the value changes, the change is reflected in the corresponding functions. Pass by value, in turn, is just sending the value to the function. In this case, a change in the value after it is sent won’t be reflected in the function. Class uses pass by reference, and Struct uses pass value.
  • Inheritance: Classes can be further inherited to form sub-classes, but Structs cannot utilize inheritance. For example, the Class Store gives its functions to the sub-class ‘grocery store’. But the Struct ‘grocery_entrance’ cannot inherit any function. We can say that there is no concept like sub-struct here.
  • Default visibility: All the members of a Class are kept as private entities by default, whereas the members of a Struct are kept as public entities by default.
  • The size of an empty Class and Struct: Class uses a size of 1 Byte even when it is empty, whereas Struct never uses any memory when it is empty. This means we can say that size of an empty struct equals 0 Bytes.
  • Garbage collection: Garbage collection is possible with Classes, as they use pass by reference. Therefore, it is easier to do the cleanup at one location where the data is stored. On the other hand, garbage collection is not possible with Struct, as it uses pass by value and the data is scattered at different locations.
  • Memory management: Because Class allows garbage collections, the memory management is also effective; however, it is not that effective with Structs.
  • Constructor: A constructor generally initializes the class with certain specified values. We can look at it like something that has been initialized with values. If a new class has to be created, the constructor is called to allocate memory for that instance. We can even pass values as arguments while calling a constructor. Let us come to our actual discussion now. Classes allow constructors of all types, such as with or without arguments, whereas structs only allow the constructors with arguments, i.e. the parameterized constructors.
  • Destructor: A destructor is called whenever we need to delete an instance of a class. The destructor, in turn, deletes that instance and frees up memory. A Class can use a destructor, whereas a Struct cannot.
  • Member Variables Initialization: In Classes, we can initialize the member variables directly; such an initialization is not possible with Structs.
  • Object Creation: The general syntax for object creation in classes is:

Demo obj = new Demo();

This means that we must use the keyword ‘new’ while creating objects of a class. This is not required when creating objects of Structs. Just take a look at their syntax:

Demo obj;

It works perfectly even without the keyword ‘new’.

When to Use Class and When to Use Struct?

As Classes are more flexible in handing data and functions together, we can go for it when the objects used are complex and large. In our example, a Mall can use the class ‘store’ to express the system in a better manner. Structs, however, are restricted to smaller objects, as they are comparatively less effective than Classes. Therefore, if you design a store of your own, Structs are the better choice.

(Video) Difference between struct and class in C#

How to Convert a Struct to a Class and Vice Versa?

You might have heard the terms ‘boxing’ and ‘unboxing’ to convert a Struct to a Class, and vice versa. Though these are effective processes to help us in the conversion, they should be handled with caution. As this directly affects the memory locations, there is a huge impact on the performance of our system. Moreover, it affects the garbage collection processes and results in overall system inefficiency. Therefore, use these conversions only when needed.

Let us look at the above-mentioned differences in tabular form.

S.NoConceptsDifferences
ClassStruct
1Re-usabilityCompletely re-usableNot re-usable
2VisibilityAll the functions of a Class are visible to its objectsThe data of an Object of a Struct is not visible to other objects of the same Struct
3Pass by Reference & pass by ValueUses Pass by ReferenceUses Pass by Value
4InheritanceThe functions of a class can be inherited by its subclasses; allows inheritanceNever allows inheritance
5Default VisibilityAll the members of a Class are private by defaultAll the members of a Struct are public by default
6Size When EmptyThe size of an empty Class is 1 ByteThe size of the empty Struct is 0 Bytes
7Garbage CollectionAs it uses pass by reference, garbage collection is possibleAs it uses pass by value, garbage collection is not possible
8Memory ManagementThe ease of the garbage collection process helps in effective memory managementThe lack of garbage collection results in poor memory management
9ConstructorsAllows constructors of all types, such as with or without parametersOnly allows parameterized constructors
10DestructorsCan use itCannot use it
11Member Variables InitializationAllows direct initialization of member variablesDoes not allow direct word initialization of member variables
12Object CreationIt is a must to use the keyword ‘new’ during object creationIt is optional to use the keyword ‘new’ during object creation
13When to Use?Better for larger and complex objects where inheritance is requiredBetter for smaller and simpler objects where inheritance is of less importance.

We have almost covered all the differences between Class and Struct, and if you feel that something is missing, please let us know. Let’s learn together and make the most of that knowledge!

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Ramalan Harifa

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Harifa, R. (2018, April 12). Difference between Class and Struct. Difference Between Similar Terms and Objects. http://www.differencebetween.net/technology/difference-between-class-and-struct/.
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Harifa, Ramalan. "Difference between Class and Struct." Difference Between Similar Terms and Objects, 12 April, 2018, http://www.differencebetween.net/technology/difference-between-class-and-struct/.

(Video) What are Value Types and Reference Types in C#? (Class vs Struct)

FAQs

What is difference between structure and class in C#? ›

Structs are value types while classes are reference types. Structs can be instantiated without using a new operator. A struct cannot inherit from another struct or class, and it cannot be the base of a class. All structs inherit directly from System.

What is the difference between a struct in C and a class in Java? ›

In C, structs are value types but in Java, classes are reference types.

Which is faster class or structure? ›

So based on the above theory we can say that Struct is faster than Class because: To store class, Apple first finds memory in Heap, then maintain the extra field for RETAIN count. Also, store reference of Heap into Stack. So when it comes to access part, it has to process stack and heap.

Can struct be null? ›

However, since structs are value types that cannot be null , the default value of a struct is the value produced by setting all value type fields to their default value and all reference type fields to null .

What is the difference between class and structure with example? ›

Structures and classes differ in the following particulars: Structures are value types; classes are reference types. A variable of a structure type contains the structure's data, rather than containing a reference to the data as a class type does. Structures use stack allocation; classes use heap allocation.

Why are classes better than structs? ›

use struct for plain-old-data structures without any class-like features; use class when you make use of features such as private or protected members, non-default constructors and operators, etc.

Can I use struct as array? ›

An array of structres in C can be defined as the collection of multiple structures variables where each variable contains information about different entities. The array of structures in C are used to store information about multiple entities of different data types.

Can a struct have a list? ›

Yes you can have a list in struct but you cannot initialise it with a field initialiser and instead you must use the constructor. Also note that you can not have a parameter-less constructor.

Is struct garbage collected? ›

Members of structs are subject to garbage collection when they leave scope, just like any other objects. The . NET GC uses a mark-and-sweep approach, where it examines objects that are pointed to by static fields, existing objects, and local variables on the stack, among others.

Is array better than structure? ›

One major difference between both of them is that- in an Array, the elements are of the same data type while a structure has elements of different data types. You can also define an Array's size during the declaration and write it in numbers within a square bracket preceded by the name of the array.

Can a struct be private? ›

A struct can indeed have public and private sections, member functions as well as member variables, and special functions such as constructors, destructors and operators.

Is struct public or private by default? ›

Because the only difference between a structure and a class is that structure members have public access by default and class members have private access by default, you can use the keywords class or struct to define equivalent classes.

How a struct is stored in memory? ›

Struct members are stored in the order they are declared. (This is required by the C99 standard, as mentioned here earlier.) If necessary, padding is added between struct members, to ensure that the latter one uses the correct alignment. Each primitive type T requires an alignment of sizeof(T) bytes.

What is class and structure in Java? ›

The class is a blueprint of a Java program. It contains information about user-defined methods, variables, and constants. Every Java program has at least one class that contains the main() method. For example: class Student //class definition.

Is struct dynamic or static? ›

Difference between Static and Dynamic Data Structures
Static Data StructuresDynamic Data Structures
The size of the static data structures is fixed and cannot be changed at runtime.The size of the dynamic data structure is not constant and can be modified at runtime.
3 more rows

Why is struct faster than class? ›

Unlike class, struct is created on stack. So, it is faster to instantiate (and destroy) a struct than a class. Unless (as Adam Robinson pointed out) struct is a class member in which case it is allocated in heap, along with everything else.

Can we declare a static class? ›

We can declare a class static by using the static keyword. A class can be declared static only if it is a nested class. It does not require any reference of the outer class. The property of the static class is that it does not allows us to access the non-static members of the outer class.

Is struct always public? ›

The only difference between a struct and class in C++ is the default accessibility of member variables and methods. In a struct they are public; in a class they are private.

Can we use for loop for struct? ›

By using the for-loop I let the user to create the struct objects. they are named as sp[i] --> sp1, sp2 etc. the problem is the objects are created. But I can use them only inside the for-loop.

Can I use vector in struct? ›

You can actually create a vector of structs!

Is struct faster than class C#? ›

The only difference between these two methods is that the one allocates classes, and the other allocates structs. MeasureTestC allocates structs and runs in only 17 milliseconds which is 8.6 times faster than MeasureTestB which allocates classes!

What is the advantage of structure over class in C#? ›

Is There a Difference between Class and Structure? 1) Structures provide better performance when we have small collections of value-types that you want to group together. 2) Use Structure if all member fields are of value type. Use Class if any one member is of reference type.

Can a struct have a constructor? ›

struct can include constructors, constants, fields, methods, properties, indexers, operators, events & nested types. struct cannot include a parameterless constructor or a destructor. struct can implement interfaces, same as class. struct cannot inherit another structure or class, and it cannot be the base of a class.

Why should I use struct instead of class? ›

Class instances each have an identity and are passed by reference, while structs are handled and mutated as values. Basically, if we want all of the changes that are made to a given object to be applied the same instance, then we should use a class — otherwise a struct will most likely be a more appropriate choice.

Does a struct need a constructor? ›

Technically, a struct is like a class , so technically a struct would naturally benefit from having constructors and methods, like a class does.

Can I use struct inside class? ›

Yes you can. In c++, class and struct are kind of similar. We can define not only structure inside a class, but also a class inside one.

Which is better array or structure? ›

One major difference between both of them is that- in an Array, the elements are of the same data type while a structure has elements of different data types. You can also define an Array's size during the declaration and write it in numbers within a square bracket preceded by the name of the array.

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