Stacks (last-in, first-out) in Intro to Computing - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a stack in computing?

A stack is a way to store items where the last item added is the first one to be removed. This is called Last-In, First-Out (LIFO). Imagine a stack of plates: you add plates on top and take plates from the top.

beginner

What does 'Last-In, First-Out' (LIFO) mean?

It means the last item you put in is the first one you take out. Like a stack of books, you add new books on top and remove the top book first.

beginner

Name two main operations of a stack.

1. Push: Add an item to the top of the stack.<br>2. Pop: Remove the item from the top of the stack.

intermediate

What happens if you try to pop from an empty stack?

This is called 'underflow'. It means there is nothing to remove because the stack is empty.

beginner

Give a real-life example of a stack.

A stack of trays in a cafeteria. You put trays on top and take trays from the top, so the last tray placed is the first one taken.

What operation adds an item to the top of a stack?

A Push

B Pop

C Peek

D Insert

Push means adding an item to the top of the stack.

If you have a stack with items A, B, C (C on top), which item will be removed first?

A A

B B

C C

D None

The last item added (C) is removed first in a stack.

What is the term for trying to remove an item from an empty stack?

A Overflow

B Underflow

C Stacking

D Push error

Underflow happens when you try to pop from an empty stack.

Which of these is NOT a stack operation?

A Push

B Pop

C Peek

D Sort

Sort is not a basic stack operation.

Stacks follow which order principle?

A Last-In, First-Out

B First-In, First-Out

C Random Access

D First-In, Last-Out

Stacks follow Last-In, First-Out (LIFO) order.

Explain how a stack works using a real-life example.

Think about how you add and remove items from a pile.

Describe what happens step-by-step when you push and then pop items from a stack.

Imagine adding and removing books from a stack.