Why does empty Structure has size 1 byte in C++ but 0 byte in C

A structure is a user-defined data type in C/C++. A structure creates a data type that can be used to group items of possibly different types into a single type. The 'struct' keyword is used to create a structure.

• C++ does not allow objects of size 0, because different objects must have distinct memory addresses.
• Therefore, even an empty class or structure in C++ occupies at least 1 byte of memory.
• This rule ensures that every object can be uniquely identified in memory.
• In C, empty structures are not standard, though some compilers (like GCC) allow them as an extension, with undefined behavior.

Note: C99 says- If the struct-declaration-list contains no named members, the behavior is undefined. 

C program with an empty structure:

#include <stdio.h>

int main()
{
    // Empty Structure
    struct empty {
    };
    
    struct empty empty_struct;

    // Printing the Size of Struct
    printf("Size of Empty Struct in C programming = %ld", sizeof(empty_struct));
}

Size of Empty Struct in C programming = 0

C++ program with an empty structure:

#include <iostream>
using namespace std;

int main()
{
    // Empty Struct
    struct empty {
    };

    // Initializing the Variable
    // of Struct type
    struct empty empty_struct;

    // Printing the Size of Struct
    cout << "Size of Empty Struct in C++ Programming = " << sizeof(empty_struct);
}