Can an object be considered as a variable?

Question

I'm having some trouble keeping apart the terms class, object, variable and datatype.

can a class be considered as a datatype? can an object be considered as a variable?

Also, what's the technical difference?

Answer 1

There are two different uses of these terms:

• Casual use:

  • Class: Abstract data type with methods and fields.
  • Object: Instance of a class.
  • Variable: Language-level name (i.e: name given by a programmer) for some piece of storage.
  • Datatype: Type that a variable (or some unnamed piece of storage) can have.

• C/C++ standard use (comes from the C standard, which isn't an Object-Oriented Language:

  • Object: Some piece of storage, whether it has a name or not.
  • Object of Class Type: Some piece of storage whose datatype is class(=struct).

Answer 2

Variables are objects with direct names.

int i;

i is a variable and an object.

int* p = new int;

*p is an object but not a variable.

Classes and types are pretty much identical, except types includes primitive types like int. Realistically, they're pretty interchangable- as well as variable/object. The reality of the C++ Standard is that very few rules apply differently to classes than to types, and variables than to objects.