Memory Layout of EntityArchetypes

Does this mean that the entities are grouped in memory in contiguous chunks?
Like this?

Code (CSharp):

1.  E1  E2  E3
2. |A,B|A,B|A,B|    <----- memory

What if I add another component, C, to E2? How would it look like?

 

The more I read, the more I think that this is actually how it is laid out in memory, can anybody confirm?

Code (CSharp):

1. // For Archetype X
2. |A1|A2|A3|   // Component A's
3. |B1|B2|B3|   // Component B's

But, again, what happens if I add component C to an entity of archetype X, when the component wasn't initially defined as part of the archetype?

 

It's the second way, when you add a component C to an Entity a new archetype will be created (it it doesn't exists yet) and the entity will be moved to it.

 

Here's a great post (which should be in the doc imo) https://forum.unity.com/threads/ecs-memory-layout.532028/#post-3513888

It moves to a new chunk. If you add C to entity number 2 it would become :

Archetype AB : |A1|A3|_____ |B1|B3|_____
Archetype ABC : |A2|____ |B2|_____|C2|____

 

Thank you @capyvara , @5argon.

@5argon I agree. That link is very helpful. Will probably direct more of my questions, if any, to that thread in the future.