Structure of a C++ Object in Memory Vs a Struct
The C++ standard guarantees that memory layouts of a C struct and a C++ class (or struct -- same thing) will be identical, provided that the C++ class/struct fits the criteria of being POD ("Plain Old Data"). So what does POD mean?
A class or struct is POD if:
- All data members are public and themselves POD or fundamental types (but not reference or pointer-to-member types), or arrays of such
- It has no user-defined constructors, assignment operators or destructors
- It has no virtual functions
- It has no base classes
About the only "C++-isms" allowed are non-virtual member functions, static members and member functions.
Since your class has both a constructor and a destructor, it is formally speaking not of POD type, so the guarantee does not hold. (Although, as others have mentioned, in practice the two layouts are likely to be identical on any compiler that you try, so long as there are no virtual functions).
See section [26.7] of the C++ FAQ Lite for more details.
Is the structure in memory of the example_struct simmilar to that in Example_Class
The behaviour isn't guaranteed, and is compiler-dependent.
Having said that, the answer is "yes, on my machine", provided that the Example_Class contains no virtual method (and doesn't inherit from a base class).
In the case you describe, the answer is "probably yes". However, if the class has any virtual functions (including virtual destructor, which could be inherited from a base class), or uses multiple inheritance then the class layout may be different.