CS Unplugged

CS Unplugged

Computer science with no computer. Every activity here is a printable worksheet or pair game you can do on your own or with a partner: for a brain break, a day the computers are down, or extra practice on one idea.

Many of these are classic unplugged activities, shared under Creative Commons licenses or in the public domain, rewritten as ready-to-print worksheets so a teacher can hand them out and a student can work through them alone. Inspired by, and partly adapted from, CS Unplugged (not affiliated); each adapted sheet credits its source at the bottom.

Warning: 9/27/2026: This is a work in progress. I have only reviewed a few of these worksheets. I expect to make many changes, fixes, and improvements in the next 2 to 12 months. Locations where you can find other free unplugged material are listed at the bottom of this page.

All activities

ActivityMSHSSoloPairMin
Algorithms
Battleships: Searching ✓ ✓ 20
Marching Orders ✓ ✓ 25
The Paper Othello Player ✓ ✓ ✓ 30
The Paper That Never Loses ✓ ✓ ✓ 30
Trace a Search ✓ ✓ 20 New set
Treasure Island ✓ ✓ 30
Binary
Binary Battleship ✓ ✓ ✓ 25 New set
Binary Battleship: 16 by 16 ✓ ✓ 35 New set
Binary Puzzles ✓ ✓ ✓ 30 New set
Count the Dots: binary numbers ✓ ✓ ✓ ✓ 30
Secret Messages in ASCII ✓ ✓ 20 New set
Secret Messages in Binary ✓ ✓ ✓ 20 New set
Secret Messages in Hex ✓ ✓ 20 New set
Secret Messages: Only Four Clues ✓ ✓ 20 New set
Boolean logic
Creature Sorting ✓ ✓ ✓ 30 New set
Creature Sorting: Real if Statements ✓ ✓ 15
Codes and ciphers
Caesar Cipher: cracking it with letter frequency ✓ ✓ ✓ 30 New set
Caesar Cipher: hiding a message in plain sight ✓ ✓ ✓ ✓ 30 New set
Vigenère Cipher: one keyword, many shifts ✓ ✓ ✓ ✓ 30 New set
Computer architecture
Little Man Computer: branches and loops ✓ ✓ 20 New set
Little Man Computer: tracing a program ✓ ✓ 20 New set
Little Man Computer: write your own ✓ ✓ 25
Data compression
You Can Say That Again! Text Compression ✓ ✓ 25 New set
Data representation
Pixel Pictures ✓ ✓ ✓ 30 New set
Pixel Pictures: how much do you save? ✓ ✓ 20
Spit-Not-So: A Word Game With a Secret ✓ ✓ 20
Graphs
The Muddy City ✓ ✓ 30 New set
The Poor Cartographer ✓ ✓ 30 New set
Tourist Town ✓ ✓ 30 New set
Lists
Trace it: lists and loops ✓ ✓ 35
Logic puzzles
Solo Battleship ✓ ✓ 20 New set
Modulo
Check Digits: catching typos with modulo ✓ ✓ 20 New set
Clocks That Wrap Around: the modulo idea ✓ ✓ 20 New set
Modulo in Real Programs ✓ ✓ ✓ 20 New set
Robot programs
Robot grid 1: moves and turns ✓ ✓ ✓ 30 New set
Robot grid 2: loops and procedures ✓ ✓ 30 New set
Robot grid 3: sensing with CAN_MOVE ✓ ✓ 30 New set
Searching
Binary Search Trees: Find the Number ✓ ✓ ✓ 20 New set
Build a Tree ✓ ✓ ✓ 15 New set
The Hidden Number Tree ✓ ✓ ✓ 20
Sorting
Beat the Clock: A Sorting Network ✓ ✓ 25 New set
Strategy games
Nim: the binary secret ✓ ✓ ✓ 25 New set
Nim: the take-away game ✓ ✓ ✓ 30
The Swap Puzzle ✓ ✓ ✓ 20

Sequenced

Short tracks that build from one activity to the next. Do them in order.

Middle school

How computers store information. Everything on a computer is 0s and 1s. Start with numbers, then work up to letters, pictures, and catching errors.

  1. Count the Dots: binary numbers 30 min
  2. Binary Battleship 25 min
  3. Pixel Pictures 30 min

Finding things fast. Search a messy list one item at a time, then a sorted list by jumping to the middle. Count the difference.

  1. Battleships: Searching 20 min
  2. Trace a Search 20 min

Heuristics. Play against a program written on paper. First one that never loses, then one that can, and find out why.

  1. The Paper That Never Loses 30 min
  2. The Paper Othello Player 30 min

Modulo: clock math. Counting around a clock that wraps back to zero, then the same idea as the % operator in code.

  1. Clocks That Wrap Around: the modulo idea 20 min
  2. Modulo in Real Programs 20 min

Binary search trees. A tree where everything smaller goes left and bigger goes right. Search one, play the hidden-number game, then build your own.

  1. Binary Search Trees: Find the Number 20 min
  2. The Hidden Number Tree 20 min
  3. Build a Tree 15 min

Graph puzzles. Towns, streets, and maps: pave the fewest roads, place the fewest ice cream vans, and color a map with the fewest colors.

  1. The Muddy City 30 min
  2. Tourist Town 30 min
  3. The Poor Cartographer 30 min

Computers follow instructions. Give exact instructions to a partner who has to follow them to the letter, then follow a map that works just like a simple machine.

  1. Marching Orders 25 min
  2. Treasure Island 30 min

High school

Python on paper. Read code the way a computer does, one line at a time, before you ever run it.

  1. Trace it: lists and loops 35 min

The AP robot. The grid-and-robot questions from the AP CSP exam, from simple moves up to programs that sense walls. Then make as many new sets as you want.

  1. Robot grid 1: moves and turns 30 min
  2. Robot grid 2: loops and procedures 30 min
  3. Robot grid 3: sensing with CAN_MOVE 30 min

Logic and codes. True and false, hidden messages, and a game you can always win once you know its binary secret.

  1. Creature Sorting 30 min
  2. Creature Sorting: Real if Statements 15 min
  3. Caesar Cipher: hiding a message in plain sight 30 min
  4. Caesar Cipher: cracking it with letter frequency 30 min
  5. Nim: the take-away game 30 min
  6. Nim: the binary secret 25 min

Little Man Computer. A whole computer on paper: 100 mailboxes, one calculator, ten instructions. Trace programs, then write your own.

  1. Little Man Computer: tracing a program 20 min
  2. Little Man Computer: branches and loops 20 min
  3. Little Man Computer: write your own 25 min

Modulo in the real world. Where % shows up in programs, then how check digits catch typos in barcodes and book numbers.

  1. Modulo in Real Programs 20 min
  2. Check Digits: catching typos with modulo 20 min

For teachers

Every sheet with a New set button can make as many fresh versions as you need; the set number prints on the sheet so you can reprint the same one. Answer keys are hidden from students: use the Show answer key link at the bottom of a sheet (or add ?key=1 to its address), then print.

Other unplugged resources

Sources this section draws on, and more places doing unplugged computer science. Many of their activities are teacher-led (whole-class games, magic tricks) rather than print-and-use.