First of all, let me describe what a stack is. Based on the name, it should be a relatively familiar concept.

Let’s assume that we have four books with the following riveting titles:

A

B

C

D

At the moment, these books are strewn out all over the floor and we want to stack them up neatly.

Four books are lying all over the place.

1 of 5

Now we have a nice neat stack of books! If we want to retrieve a book from this stack, we can take the book on top. Taking a book from the bottom is a bit precarious and we don’t want to topple the entire stack. Therefore, we’ll take down the top book on the stack and read it or do whatever we want to do with it.

Let’s say we want to take Book A. Right now, it is at the bottom of the stack, so we need to take Book D, put it down, then do the same for Book C and Book B, and then we can access Book A.

This is the main idea of a stack. The data structure stack is very similar to a physical stack that you’d most likely be familiar with. The stack data structure allows us to place any programming artifact, variable or object on it, just as our example stack allowed us to put books in it.