Abstract types can be handled by code that does not know or "care" what underlying types are contained in them. Programming that is agnostic about...

 Abstract types can be handled by code that does not know or "care" what underlying types are contained in them. Programming that is agnostic about concrete data types is called generic programming. Arrays and records can also contain underlying types, but are considered concrete because they specify how their contents or elements are laid out in memory give examples of the same