CS110 Computing Principles Lab 1
Broadcast, Animations, and Music!
Learning Goals
Resources
User Interface Detective Work
Broadcast
Wrap Up
Let's open up Scratch! You will see a screen like the one shown below. Explore the aspects of the user interface highlighted in red. Play around for a while and see if you can figure out the major components of the interface. In the next step, you will make your first project and explore further.
For your first project, make a quick song! You will find the following blocks in the Sound tab useful; feel free to change the default numbers as you see fit:
While you are working on it, try to figure out how to connect and disconnect blocks, and how to remove a piece from inside a long script. Also, what do you think is the difference between these two blocks?
and 
Hint: Try to use many copies of one of the blocks in a row, and hear the result. Do this for each block.
As we explore Scratch and as we learn new ideas in computer science, you will be seeing a few words and terms that you may not understand. We will always try to define new vocabulary in our Lingo List. Below, we show some terms that we will use for the various items in Scratch. Keep thinking of more as the class continues!
Scratch Lingo
| Tabs (for blocks) |  |
| Tabs (per sprite) |  |
| Blocks |  |
| Script |  |
| Sprite |  and  |
| Costume (Each sprite can have multiple costumes.) |  |
| Stage |  |
More Computer Science Lingo
Experiment with a short Scratch play
Scripts - Try to make these scripts in Scratch! You will find that the Cat and the Duck have completely separate script areas. Click on each character to see their script area. Once you are done, press the green flag to start the short play.
A note about style: You will notice that we chose to name the messages that were broadcast so that it would help us keep track of what we were doing and what messages we were sending. We recommend that you do this in your projects!
Hints
1. To choose a new sprite from a library of existing sprites, click on the icon below the stage that looks like a folder.
2. Try to figure out what the commands (whose images are on the left) and buttons (whose images are on the right) do. These will be helpful to get the characters to face each other.
Exercise - Once you have this working, change the script of the "play" so that each character says an additional line.
It can be helpful to see which block is executing at each time. Click Edit and then Start Single Stepping to highlight the block that is executing when you run the scripts.
Once you are done, click Edit and then Stop Single Stepping to stop the single-stepping process.
1. Without trying this in Scratch, try to answer the following question:
What does the following set of scripts for the Cat do when you click on the "When I receive Turn1" script?
Choose one answer.
Test Yourself: Different Ways to Broadcast
1. How many times will you hear the meow sound when you run the script below?
2. How many times will you hear the meow sound when you run the script below?
3. How many times will you hear the note 60 play when you click on the green flag?
4. How many times will you hear the note 60 play when you click on the green flag?
5. How many times will the sound meow be played when we click the green flag?
6. How many times will the sound meow be played when we click the green flag?
By this point, you have probably figured out how to save your Scratch projects, but you can also save individual Sprites separately.
To save (or export) a Sprite, right-click on the sprite and select export this sprite. To load (or import) a Sprite, click on the icon with a folder next to New Sprite (circled in yellow in the image below) and select the Sprite that you want to add to your project.
Try to make an electric keyboard! The code below shows a start:
Hint: You might want to print or draw a piano keyboard or a computer keyboard to keep track of how you have mapped keys to notes. We have provided a few images below that you can print out to work with.
Challenge: Add additional functionality, perhaps by adding scripts for other keys on the computer keyboard, so that your electric keyboard can change Volume, Instrument, and/or Tempo.
Get Familiar With Scratch - The main idea behind this homework is to get more comfortable with Scratch, so play around and try new things! Be sure to make a note if there is anything that seems confusing, and ask your lab assistants about it later. Activities