pxt-calliope/docs/reference/js/lessons/column/quiz.md

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2016-03-26 00:47:20 +01:00
# cascade quiz
Learn how to create a blinking LED script with a for loop. #LED #screen #plot #docs
## Name
## Directions
Use this activity document to guide your work in the [light column cascade tutorial](/microbit/js/light-column-cascade/tutorial).
Answer the questions below while working on or after you finish the tutorial. Pay attention to the dialogs!
## 1. What is a for loop?
## 2. Consider the following code
```
for (let i = 0; i < 5; i++) {
for (let j = 0; j < 5; j++) {
led.plot(i, j)
}
}
```
If the rectangle below represents a board that is 5 LEDs wide and 5 LEDs tall, place an X approximately all the locations where the LED is lighted. Explain why the LED is lighted there.
![](/static/mb/empty-microbit.png)
## 3. Consider the following code
```
for (let i1 = 0; i1 < 3; i1++) {
for (let j1 = 0; j1 < 3; j1++) {
led.plot(i1, j1)
}
}
```
If the rectangle below represents a board that is 5 LEDs wide and 5 LEDs tall, place an X approximately all the locations where the LED is lighted. Explain why the LED is lighted there.
![](/static/mb/empty-microbit.png)
## 4. Consider the following code
```
for (let i2 = 0; i2 < 2; i2++) {
for (let j2 = 0; j2 < 2; j2++) {
led.plot(i2, j2)
}
}
```
If the rectangle below represents a board that is 5 LEDs wide and 5 LEDs tall, place an X approximately where the LED is lighted. Explain why the LED is lighted there.
![](/static/mb/empty-microbit.png)
******************************
## KEY
## Directions
Answer the questions below while working on or after you finish the tutorial.
## 1. What is a for loop?
Answers will vary. In general, for loop refers to the code that repeats for a fixed number of times. We specify the LED using x, y coordinates.
## 2. Consider the following code
```
for (let i3 = 0; i3 < 5; i3++) {
for (let j3 = 0; j3 < 5; j3++) {
led.plot(i3, j3)
}
}
```
If the rectangle below represents a board that is 5 LEDs wide and 5 LEDs tall, place an X approximately where the LED is lighted. Explain why the LED is lighted there.
![](/static/mb/lessons/cascade-0.png)
This code turns on specific LED. Plot turns on the specified LED on the LED screen. We specify the LED using x, y coordinates. The code lights on the LEDs
x - the x coordinate or horizontal position (0,1,2,3,4)
y - the y coordinate or vertical position (0,1,2,3,4)
## 3. Consider the following code
```
for (let i4 = 0; i4 < 3; i4++) {
for (let j4 = 0; j4 < 3; j4++) {
led.plot(i4, j4)
}
}
```
If the rectangle below represents a board that is 5 LEDs wide and 5 LEDs tall, place an X approximately where the LED is lighted. Explain why the LED is lighted there.
![](/static/mb/lessons/column-0.png)
This code turns on specific LED. Plot turns on the specified LED on the LED screen. We specify the LED using x, y coordinates.
x - the x coordinate or horizontal position (0,1,2)
y - the y coordinate or vertical position (0,1,2)
## 4. Consider the following code
```
for (let i5 = 0; i5 < 1; i5++) {
for (let j5 = 0; j5 < 1; j5++) {
led.plot(i5, j5)
}
}
```
If the rectangle below represents a board that is 5 LEDs wide and 5 LEDs tall, place an X approximately where the LED is lighted. Explain why the LED is lighted there.
![](/static/mb/lessons/column-1.png)
This code turns on specific LED. Plot turns on the specified LED on the LED screen. We specify the LED using x, y coordinates.
x - the x coordinate or horizontal position (0,1)
y - the y coordinate or vertical position (0,1)