pxt-calliope/olddocs/lessons/strobe-light/quiz-answers.md

strobe light quiz answers

Learn how to create a blinking images with a for loop.

This is the answer key for the strobe light quiz.

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 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 where the LED is lighted. Explain why the LED is lighted there.

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 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 where the LED is lighted. Explain why the LED is lighted there.

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 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.

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)