The big ideaAn event, like a tap, can send a message that makes other things happen.
How it works
Something that happens is called an event. A tap, a key press, a click or a timer can be an event.
An event can send a message, and everyone who is listening can act on it.
Each helper listens for the same message. Here the message is start.
One signal starts everyone at once, so nobody has to guess.
When the message start comes.
Example 1: A bell is a signal
At practice, Ms. Okoro holds up a little brass bell.
When the bell rings, the helpers start. The ring is the signal.
Ding! Tavi's lights glow on, right on time.
Example 2: An event sends a message
Tavi makes a start button on a screen.
When the button is tapped, the tap is the event.
The event sends the message start.
Example 3: Listening
Tavi's rule says: when start is heard, switch on the lights.
The message start is sent.
Tavi hears it, so the lights come on.
A helper listens for the message start.
Example 4: Everyone acts
Mina listens for start too, and so does Bo.
The music begins and the curtain swishes open.
One message reaches all three helpers.
Words to know
event
Something that happens, like a tap.
message
What an event sends, like start.
signal
A message that tells everyone to begin.
listen
To wait for a message so you can act on it.
Watch out
The event is what happens, like the tap. The lights and the music happen because of it.
A lamp that is already on, a quiet room, a picture on the wall and a sleeping robot are not events, because nothing happens.
Every helper must listen for the same message, or one will miss it.
With no signal, everyone guesses, and that makes a muddle.
Try it
Is a mouse click an event?
Is a quiet room an event?
A key press starts the music. Which is the event, the press or the music?
Why use one signal for everyone?
Answers: 1. Yes · 2. No · 3. The key press · 4. So everyone starts together
Try at homePick three jobs, like a light, a song and a bow. Agree on one signal, like a clap or a bell. When the grown-up gives the signal, every job begins together. Then try it without a signal and see the muddle.
For grown-upsPlay the Mission: pick three jobs, like a light, a song and a bow, and agree on one signal, like a clap or a bell. When you give the signal, every job begins together. Then try it without a signal and see the muddle.
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