What makes an object?

A good answer might be:

Here is my unofficial list:

Characteristics of Objects

The first item in this list is too restrictive. For example, you can think of your bank account as an object, but it is not made of material (although you and the bank may use material in keeping track of your account, your account exists independently of this material.) Although it is not material your account has properties (the balance, interest rate, owner) and you can do things to it (deposit money, cancel it) and it can do things (charge for transcactions, appreciate interest.)

The last three items on the list seem clear enough. In fact, they have names:

This is a somewhat ordinary description of what an object is like. Do not be surprised if other notes and books have a different list. When you start writing object-oriented software you will find that it is hard to decide exactly what your objects are.

QUESTION 3:

Consider a tube of four yellow tennis balls.