Remember: An event, like a tap, can send a message, and everyone who is listening can act on it. One signal starts everyone together.
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Read the story, then answer.
One signalThe Tinker Club is putting on a show for the whole school. Tavi runs the lights, Mina plays the music and Bo opens the curtain. But at practice, Bo opens the curtain far too soon, and then the music starts before the lights come on. What a muddle! Ms. Okoro holds up a little brass bell and says, "When the bell rings, you start. The ring is your signal." In coding, something that happens is called an event, and an event can send a message. Each helper listens for the same message, and the message is start. On the big day, Tavi taps a start button. Ding! The message flies out, the lights come on, the music begins, and the curtain swishes open right on time.
1
Tavi taps the start button. What is the event?
The curtain openingThe music playingThe tap on the button
2
An event can send a , and everyone listening can act.
messagesongcurtain
3
A timer running out can be an event.
TrueFalse
4
Circle every event.
A key pressA lamp that is already onA mouse clickA sleeping robotA timer running out
5
Tavi's rule is below. The message start is sent. What does Tavi do?
Plays the musicOpens the curtainSwitches on the lights
6
Each helper must guess when to begin.
TrueFalse
Send and hear
7
Join each helper to the job they do when they hear start.
1Tavi
2Mina
3Bo
4Ms. Okoro
Arings the bell, the signal
Bplays the music
Cswitches on the lights
Dopens the curtain
8
Put the chain in order, from the first thing that happens.
The lights, music and curtain begin
Tavi, Mina and Bo hear it
Ms. Okoro rings the bell
The ring is the signal
9
Tavi's rule runs the lights, Mina's the music and Bo's the curtain. Tavi taps the button, and the message start is sent. Who does not act?
MinaTaviBo
10
Mix-up to fix: Bo's rule listens for the wrong message. Which change fixes it?
Change Bo's rule to: when start is heardTap the button twiceChange Tavi's rule to: when stop is heard
11
Stretch: Tavi taps start once. The one message reaches Tavi, Mina and Bo, and things begin.
12
Pick three jobs, like a light, a song and a bow. Write the one signal that starts them, and the three jobs.
13
Draw the start button and an arrow to each of the three helpers.
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Answer key · Set A
The Tinker Club show
1The tap on the button The tap is something that happens, so it is the event. The music and the curtain happen because of it.
2message The event sends the message start, and the helpers who listen can act.
3True A tap, a key press, a click or a timer can all be events.
4A key press, A mouse click, A timer running out A key press, a click and a timer running out each happen. A lamp that is already on and a sleeping robot do nothing until something wakes them.
5Switches on the lights Tavi listens for start, and when start comes she switches on the lights.
6False One signal can start everyone at once. Guessing makes a muddle.
71-C, 2-B, 3-D, 4-A Each helper has a job, and the bell is the signal at practice.
84, 3, 1, 2 First something happens, then the message goes out, then the listeners hear it, and then they act.
9Bo Bo listens for stop, not start, so he does not hear the message that was sent.
10Change Bo's rule to: when start is heard Every helper must listen for the same message, and here the message is start.
113 The lights, the music and the curtain all begin from one message.
12Your own words: a grown-up reads it.
Mark each answer, count the right ones and write the score on the sheet.