Class vs Struct: Difference and Comparison

The question of whether to use a class or a struct is common among C++ programmers while designing code. Amongst the youngest developers, there is a cloud of misconception about the difference between class and struct technically. Even after understanding differences, developers sometimes disagree about more appropriate code.  

In .NET, there are two categories of kinds, class, a reference type, and struct, a value type. Reference type mainly lives on the heap, whereas a value type lives in line. This article can clear up several other differences. 

Key Takeaways

1. Classes are reference types, while structs are value types, affecting how they store and access data.
2. Structs cannot inherit from other structs or classes, whereas classes support inheritance.
3. Classes can have destructors to release resources, while structs do not support destructors.

Class vs Struct 

The difference between class and struct is that classes are reference types allocated on the heap and garbage collection. On the other hand, the struct is a value type allocated either on the inline or stack-containing types.  

A class present in C++ is quite similar to a C structure. It consists of a data members list and operations set performed on the class. It can be said that in object-oriented programming, a class is the building block. Class is also similar to the blueprint of an object.  

A struct is a data type of value type. It helps to make a single variable hold linked data of several types. While creating a structure, the keyword “struct” is used. When a struct object is created using the new operator, then the appropriate constructor is called, and it gets created. 

Comparison Table

Parameters of Comparison	Class	Struct
Default visibility	Private	Public
Size when empty	1 Byte	0 Bytes
Members variables initialization	Allows	Does not allow
Garbage collection	Possible because it uses pass by reference	Not possible because it uses pass by value
Re-usability	Completely	Not

What is Class? 

In C++ programming, a class is a data structure or user-defined type that has functions and data as its members. The default access is private to the C++ class members. The private members fail to access outside the class and can only be accessed through the class methods. Inheritance is allowed in class because its function can be inherited by its subclasses.

Class data type instances are known as objects. It can contain member functions, overloaded operators, and variable constants defined by the programmer. With the help of class templates, the class declaration can be generated. These class templates represent a class family.  

The declaration of an actual class is obtained by template instantiating with one or more arguments of the template. Template specialization is defined as an instantiation of a template with a specific set of arguments. The C++ syntax tries to make structures in every aspect look like that of the basic data types. 

The classes of C++ have their members. Members of classes are declared to be either privately or publicly accessible by specifiers, respectively. After a specifier, if any member is encountered will have the associated access unless another specifier is encountered. 

What is Struct? 

In a word, a struct stands for a bundle. It is several related elements that are required to be tied up together in a context in a certain way. This kind of context can be passing a number that is restricted of arguments to a function.  

In terms of the C programming language, it is a composite data type declaration. It defines a physical variable grouped list under one name in the memory block. It allows the different variables to be accessed through a single point or through the struct declared name that returns the address, which is the same. 

The struct can contain other data types so to be used for records with the mixed data type or other mixed types. In C, it references a physical memory’s contiguous block, delimited by boundaries of word length. As a result, each field is located at a fixed certain offset from the very start.   

When it comes to C++ language, a struct is similar to a C++ class, but the default visibility is quite different. It can be dynamically allocated or is statically allocated either on the heap or the stack with an explicit pointer. The default visibility of struct in C++ is private. 

Main Differences Between Class and Struct 

1. Class is better to use when objects are complex and large, and inheritance is required, while for simpler and smaller, it is better to use struct where inheritance is of less importance.  
2. When it comes to visibility, all the functions are visible to the objects of the class. But the struct objects data is not visible to other objects related to the same struct.  
3. All types of constructors are allowed in class, such as without or with parameters. On the other hand, struct allows only parameterized constructors.  
4. The class has effective memory management due to the ease of the garbage collection process, whereas struct results in poor memory management because it lacks garbage collection.  
5. In terms of inheritance, it is allowed in class because its function can be inherited by its subclasses. On the flip side, struct never allows inheritance. 

References

1. https://link.springer.com/chapter/10.1007/978-3-319-96418-8_50
2. http://www.openrce.org/articles/files/jangrayhood.pdf