Hour of Code · Unplugged activity
Programming on a Map
20 min
Move a character across a grid using only direction commands, and discover what an algorithm really is.
What it teaches
Sequencing and algorithms. A computer only does exactly what it is told, in order. Here you are the programmer and a classmate is the computer: you write a precise list of steps, they follow it to the letter. When the character misses the goal, you have found a bug, and fixing it is debugging.
What you'll need
- A printed 5x5 grid (or draw one on paper or a whiteboard).
- A start square, a goal (a carrot), and one obstacle to avoid.
- Four command words: Up, Down, Left, Right.
How to run it
- 1
Place the character on the start square and the carrot on another square. Add one obstacle square between them.
- 2
One student is the programmer: they write a list of commands (for example: Right, Right, Up, Up) to move the character step by step.
- 3
A second student is the computer: they read the list out loud and move the character exactly one square per command, no guessing.
- 4
If the character hits the obstacle or misses the carrot, that is a bug. Find the wrong command, fix it, and run the program again.
- 5
Swap roles and make it harder: more obstacles, a longer path, or a rule that the character may only turn, never move diagonally.
Try it now
The character starts bottom-left and the carrot is two squares right and two squares up, with an obstacle directly between them on the diagonal. Can you write a command list that reaches the carrot without crossing the obstacle? (One answer: Right, Right, Up, Up. Another: Up, Up, Right, Right. Both work; there is rarely only one correct algorithm.)
Talk about it
Ask the class: what happens if two commands are swapped? Real programs break the same way. Precise order is everything.
Developed by alphaPlan Center.
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