7.2: Structures in C++

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In C++, a structure is the same as a class except for a few differences. The most important of them is security. A Structure is not secure and cannot hide its implementation details from the end user while a class is secure and can hide its programming and designing details. Following are the points that expound on this difference:

1) Members of a class are private by default and members of a struct are public by default.
For example program 1 fails in compilation and program 2 works fine.

// Program 1 
#include <iostream>
using namespace std 

class Test { 
    int x; // x is private 
}; 

int main() 
{ 
   Test t;

   t.x = 20; // compiler error because x is private 
   return 0; 
}

BUT...if we use a struct instead of class we get a different result

// Program 2
#include<iostream>
using namespace std;

struct Test {
   int x; // x is public
};

int main()
{
   Test t;
   t.x = 20; // works fine because x is public
   return 0;
}

Adapted from:
"Structure vs class in C++" by roopkatha, Geeks for Geeks is licensed under CC BY-SA 4.0