1. Introduction to The Whole Numbers

Introduction

As we know, we use 1, 2, 3, 4,... when we begin to count. They come naturally when we start counting. Hence, mathematicians call the counting numbers as Natural numbers. 
    
    Predecessor and successor
    Given any natural number, you can add 1 to that number and get the next number i.e. you get its successor. The successor of 16 is 16 + 1 = 17. 
    Similarly, if we substract 1 from that number we get predecessor of that number, the predecessor of 20 is 20 – 1 = 19. 

Whole Numbers

The numbers 1, 2, 3, ...., are called natural numbers or counting numbers. Let us add one more number, i.e., zero (0), to the collection of natural numbers. Now the numbers are 0, 1, 2, 3, ..... These numbers are called whole numbers.