• What is the difference between C structures and C++ structures?
• Comparison chart of C structures vs C++ structures?
• Can I define a function in a struct?
• Is it possible to set default values for C struct members?
• Do C structures support access modifiers?
• C structures vs C++ structures
• Can we declare a function inside the structure of C programming?

If you are asking any of the above questions, well you have come to the right place. In this tutorial, you will learn the difference between C structures and C++ structures. First, let’s see the comparison chart for C and C++ structures, then I will discuss the difference with some programming examples.

Differences Between the C Structures and C++ Structures:

The following comparison chart explains the difference between C structures and C++ structures.

The above comparison chart is for a quick summary of the differences between C and C++ structures. Now let’s see some important differences with programming examples.

1. Member functions ( function inside the structure):

In C: NO

We can not create a function using the structure. If you will try to implement the function in C structures, you will get the compiler error.

struct A
{
    //member function
    void foo() //<---- compiler error
    {

    }
};

In C++: Yes

We can create a member function in C++ structures like the class.

struct A
{
    //member function
    void foo()
    {

    }
};

2. Default values to member variable:

In C: No

It is not possible to assign a default value to the structure attribute.

struct A
{
    //member variable
    int data = 7; //<--- compiler error
};

The structure is a data type. You don’t give values to a data type. You give values to variables of data types. See the below example,

#include<stdio.h>

struct A
{
    //member variable
    int data;
};

int main()
{
    //_A is structure variable
    struct A _A = {5};

    printf("_A.data = %d\n", _A.data);

    return 0;
}

Output: _A.data = 5

In C++: Yes

Yes, we can assign the default value.

struct A
{
    //member variable
    int data = 7;
};

3. static members variables:

In C: No

It is not possible to create a static member variable in C.

struct A
{
    //member variable
    static int data; //<--- compiler error
};

In C++: Yes

Yes, we can create a static member variable in C++.

struct A
{
    //member variable
    static int data;
};

4. Instantiation:

In C during instantiation, we have to use the struct keyword whereas in C++ we don’t need to use the struct keyword.

In C:

#include<stdio.h>

struct A
{
    //member variable
    int data1;
    int data2;
};


int main()
{
    struct A sData = {27, 24};

    printf("%d %d", sData.data1,sData.data2);

    return 0;
}

Output: 27 24

In C++:

#include<stdio.h>

struct A
{
    //member variable
    int data1;
    int data2;
};


int main()
{
    /*Not necessary to use struct
    keyword*/
    A sData = {27, 24};
    printf("%d %d", sData.data1,sData.data2);

    return 0;
}

Output: 27 24

5. Constructor and Destructor:

In C: Not possible.

In C we can not create a constructor inside a structure.

#include<stdio.h>

struct A
{
    A() //<--- compiler error
    {

    }
};


int main()
{
    return 0;
}

In C++: Yes possible.

We can create a constructor inside a structure in C++.

#include<stdio.h>

struct A
{
    A()
    {

    }
};


int main()
{
    return 0;
}

6. Access modifiers:

C++ structures have access modifiers but C structures do not have these modifiers. C++ has three access modifiers, public, private, and protected.

7. sizeof():

A sizeof operator will give 0 for an empty structure in C whereas 1 for an empty structure in C++.

In C:

#include<stdio.h>

struct A
{
//empty struct
};

int main()
{
    printf("%d", sizeof(struct A));

    return 0;
}

Output: 0

In C++:

#include<iostream>

struct A
{
 //empty struct
};

int main()
{
    std::cout << sizeof(A);

    return 0;
}

Output: 1

8. Inheritance and data hiding:

C structures do not support inheritance and data hiding because C is not an object-oriented language.

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