Deciphering Object Sizes of some classes - Why don't they appear the same as the calculated ones?

Question

I must first show you some sizeof results in CppDroid:

sizeof(int) -> 4
sizeof(double) -> 8
sizeof(char) -> 1

Now I tried deciphering some class object sizes using sizeof.

I read somewhere that classes have the size of the members added together.

So In my class:

class Memory { char a; }m;
cout<<sizeof(m); //Shows 1.

But,

class Memory2 { char a; int b; }m;
cout<<sizeof(m); //Shows 8?

And In derived classes, I get:

class I:public Memory2
{ char aaa;} i;
cout<<sizeof(i); //Shows 16?

Why ?

Answer 1

Have you maybe read this?

http://www.cprogramming.com/tutorial/size_of_class_object.html

Answer 2

Is it due to use of a different compiler or is the compiler playing safe by reserving some extra memory for the class objects?

Answer 3

I would appreciate it more if I recieved an answer for my question as well...😐😶

Answer 4

@Dplusplus
I was aware of only step one, and hadn't read this before.
Thank You very much!