CONCEPT OF THE NUMBER "0"

The idea of appending the thing called "0" to our number system, giving it a symbol and using it, was a real step for human intellect. Why? Because it is not a number. It is something different. It is like adding an orange to a basket of apples and calling it an apple. It is an unusual thing to do that a person wouldn't ordinarily think of doing. Before the invention of using a "0" the number system consisted of just the positive integers and something constructed from the integers, fractions, for working with continuous quantities. We know what an integer is just as we know what a dog is, a cat is or a human is. We have an intuitive knowledge of what it is and to add something completely different to the set of integers and call it an integer and treat it as an integer is unorthodox and strange and who would think of doing it? The concept of "0" is "nothing". Who would think of giving "nothing" a symbol and a name and appending it to the set of integers and considering as an integer?