Push / Pop

Overview

Push and pop are the two fundamental operations that define how a stack behaves. Both operations work only at the top of the stack. Push adds a new element to the top, and pop removes the element currently at the top.

Push Operation

Pushing means placing a new value on top of the stack. The new element becomes the most recent item, and the previous top element moves just below it. Because stacks only allow adding at the top, the push operation is simple and efficient.

How Push Works

When a value is pushed onto the stack, the stack grows upward. No shifting of elements is required, and no part of the structure besides the top is affected. This makes push very fast in most implementations.

Pop Operation

Popping means removing the element currently on top of the stack. Only the most recent element can be removed. After a pop, the element below the removed one becomes the new top of the stack.

How Pop Works

During a pop, the top element is returned and then removed from the stack. Nothing else needs to shift. The operation is fast because the stack always knows which element is at the top.

Why Push and Pop Are Efficient

Both operations work only at a single fixed position: the top. Because no other elements are moved or examined, push and pop are both quick and predictable, making stacks ideal for tasks that require controlled order and fast access to the most recent value.