Difference Between Class and Struct (With Table)

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 generally two categories of kinds, class which is a reference type and struct is a value type. Reference type mainly lives on the heap, whereas a value type lives in line. Several other differences can be cleared up by this article. 

Class vs Struct 

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

A class present in C++ is quite similar to a C structure. It consists of a data members list and operations set generally 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 Between Class and Struct 

Parameters of ComparisonClassStruct
Default visibilityPrivatePublic
Size when empty1 Byte0 Bytes
Members variables initializationAllowsDoes not allow
Garbage collectionPossible because it uses pass by referenceNot possible because it uses pass by value
Re-usabilityCompletelyNot

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 every aspect to 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 encountered will have the associated access unless another specifier is encountered. 

What is Struct? 

In a word, a struct generally 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 generally 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, generally 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. 

Conclusion 

It can be concluded that both class and struct are common among C++ programmers. Class is reference type which is allocated on the heap as well as garbage collection. On the flip side, the struct is a value type that is allocated either on the inline or stack in containing types.  

When it comes to visibility, the default visibility is private in class, whereas it is public in a struct. Garbage collection is possible in class because it uses pass-by-reference. On the other hand, in the struct, garbage collection is not possible because it uses the pass-by-value. The size of the class is 1 byte when it is empty, while in struck, it is 0 bytes. 

References 

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