The most important difference between structures and classes is security. Structures are insecure because they cannot hide their implementation details, while classes can hide their programming and design details. In this article, we will discuss the differences between structures and classes in C++. But before discussing the differences, we will understand the definitions of structures and classes in C++.
What is a Structure in C++?
A structure is a collection of variables of different data types referenced by the same name. A structure declaration serves as a template for creating structure instances.
Syntax:
The syntax for a structure is as follows:
struct Structurename{ Struct_member1; Struct_member2; Struct_member3; . . . Struct_memberN;};The keyword “struct” tells the compiler that a structure has been declared. “Structurename” defines the name of the structure. Since a structure declaration is considered a statement, it typically ends with a semicolon.
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What is a Class in C++?
A class in C++ is similar to a structure in C; it consists of a set of data members and a set of operations performed on the class. In other words, a class is a fundamental building block of object-oriented programming. It is a user-defined object type that has its own set of data members and member functions, which can be accessed and used by creating class instances. A C++ class is like a blueprint for an object.
Syntax:
The syntax for classes and structures is similar. The syntax for a class in C++ is as follows:
class class_name{ // Private data members and member functions Access specifier; Data member; Member functions (member list) { . . }};In this syntax, “class” is a keyword that tells the compiler that a class has been declared. The main feature of object-oriented programming is data hiding, achieved through three access specifiers: “public”, “private”, and “protected”. If an access specifier is not specified when declaring data members or member functions in a class, they are considered private by default.
The public access specifier allows others to access program functions or data. Members of a class can only access the private members of the class. The protected access specifier is used in inheritance. If an access specifier has already been declared, it cannot be changed again in the program.
Main Differences Between Structures and Classes
Here are the main differences between structures and classes. Some of these differences are as follows:
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By default, all members of a structure are public, while all members of a class are private.
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Structures automatically initialize their members, while classes use constructors and destructors to initialize members.
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When implementing a structure, memory is allocated on the stack; whereas in a class, memory is allocated on the heap.
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Variables in a structure cannot be initialized at declaration, while they can in a class.
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Any member of a structure cannot be null, while class variables can be null.
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Structures are value types, while classes are reference types.
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Special methods can be used to describe operators for handling new forms of data.
Comparison Between Structures and Classes
Below we will discuss a detailed comparison between structures and classes. Some of these are as follows:
| Feature | Structure | Class |
|---|---|---|
| Definition | A structure is a collection of variables of different data types referenced by the same name. | A class in C++ is defined as a collection of related variables and functions contained within a single structure. |
| Basic Case | If no access specifier is specified, all members are set to “public”. | If no access specifier is defined, all members are set to “private”. |
| Declaration | struct structure_name{ type struct_member1; type struct_member2; type struct_member3; . type struct_memberN; }; | class class_name{ data member; member function; }; |
| Instance | A structure instance is called a “structure variable”. | A class instance is called an “object”. |
| Inheritance | Does not support inheritance. | Supports inheritance. |
| Memory Allocation | 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 | Used for small amounts of data. | Used for large amounts of data. |
| Null Value | Not possible | Can be null. |
| Need for Constructors and Destructors | Can only have parameterized constructors. | Can have all types of constructors and destructors. |
Similarities
There are the following similarities between structures and classes:
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Both classes and structures can declare any private members.
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Both classes and structures support the inheritance mechanism.
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The syntax for classes and structures is the same in C++.
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The names of classes or structures can be used as independent types.
Conclusion
In C, structures have some limitations, such as not being able to hide data, not being able to treat structure data as built-in types, and lacking inheritance support. C++ structures overcome these shortcomings.
A structure in C++ is an extended version called a class. Programmers can simplify the handling of data and functions using classes, while structures are used solely for holding data.
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