setup() and loop() execution model in Arduino - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define the setup function that runs once.

Arduino

void [1]() {
  // initialization code here
}

Drag options to blanks, or click blank then click option'

Asetup

Bstart

Cloop

Dmain

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'loop' instead of 'setup' for initialization.

The setup() function runs once when the Arduino starts. It is used to initialize settings.

2fill in blank

medium

Complete the code to define the loop function that runs repeatedly.

Arduino

void [1]() {
  // code to run repeatedly
}

Drag options to blanks, or click blank then click option'

Arepeat

Bsetup

Cloop

Dmain

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'setup' instead of 'loop' for repeated code.

The loop() function runs over and over after setup() finishes. It contains the main code that keeps running.

3fill in blank

hard

Fix the error in the code to ensure the loop function runs repeatedly.

Arduino

void setup() {
  // initialization
}

void [1]() {
  // repeated code
}

Drag options to blanks, or click blank then click option'

Astart

Bloop

Crun

Dbegin

Attempts:

3 left

💡 Hint

Common Mistakes

Naming the loop function incorrectly.

The Arduino expects a function named loop() to run repeatedly. Using any other name will not work.

4fill in blank

hard

Fill both blanks to create a program that blinks an LED on pin 13.

Arduino

void [1]() {
  pinMode(13, [2]);
}

void loop() {
  digitalWrite(13, HIGH);
  delay(1000);
  digitalWrite(13, LOW);
  delay(1000);
}

Drag options to blanks, or click blank then click option'

Asetup

BOUTPUT

CINPUT

Dloop

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'INPUT' instead of 'OUTPUT' for pin mode.

The setup() function runs once to set pin 13 as an output using OUTPUT. The loop() function then blinks the LED.

5fill in blank

hard

Fill all three blanks to create a program that reads a button on pin 2 and turns on an LED on pin 13 when pressed.

Arduino

void [1]() {
  pinMode(13, [2]);
  pinMode(2, [3]);
}

void loop() {
  int buttonState = digitalRead(2);
  if (buttonState == HIGH) {
    digitalWrite(13, HIGH);
  } else {
    digitalWrite(13, LOW);
  }
}

Drag options to blanks, or click blank then click option'

Asetup

BOUTPUT

CINPUT

Dloop

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up INPUT and OUTPUT pin modes.

The setup() function sets pin 13 as OUTPUT for the LED and pin 2 as INPUT for the button. The loop() reads the button and controls the LED accordingly.

Practice

1. What is the main purpose of the setup() function in an Arduino program?

easy

A. To stop the Arduino program

B. To run code repeatedly forever

C. To reset the Arduino board

D. To run code once at the start to prepare the Arduino

Solution

1. Step 1: Understand the role of setup()

   The setup() function runs only once when the Arduino starts. It is used to prepare things like pin modes or initial settings.

2. Step 2: Compare with other options

   loop() runs repeatedly, so To run code repeatedly forever is incorrect. Options A and D describe actions not done by setup().

3. Final Answer:

   To run code once at the start to prepare the Arduino -> Option D

4. Quick Check:

   setup() runs once = C [OK]

Hint: Remember: setup() runs once, loop() runs forever [OK]

Common Mistakes:

• Thinking setup() runs repeatedly
• Confusing setup() with loop()
• Believing setup() resets the board

2. Which of the following is the correct way to declare the loop() function in Arduino?

easy

A. int loop() {}

B. void loop() {}

C. void loop(void) {}

D. loop() void {}

Solution

1. Step 1: Recall Arduino function syntax

   Arduino functions like loop() are declared with return type void and empty parentheses: void loop() {}.

2. Step 2: Check each option

   void loop() {} matches correct syntax. int loop() {} wrongly uses int return type. void loop(void) {} is valid C++ but less common in Arduino examples. loop() void {} has incorrect order.

3. Final Answer:

   void loop() {} -> Option B

4. Quick Check:

   Standard Arduino loop syntax = A [OK]

Hint: Use 'void loop()' exactly as Arduino expects [OK]

Common Mistakes:

• Using wrong return type like int
• Swapping order of function name and return type
• Adding parameters inside loop()

3. What will be the output on the Serial Monitor when running this Arduino code?

void setup() {
  Serial.begin(9600);
  Serial.println("Start");
}

void loop() {
  Serial.println("Looping");
  delay(1000);
}

medium

A. Start and Looping printed once each

B. Only Looping printed repeatedly

C. Start printed once, then Looping printed every second

D. No output because Serial.begin() is missing

Solution

1. Step 1: Analyze setup() output

   Serial.begin(9600) starts serial communication. Serial.println("Start") prints "Start" once at the beginning.

2. Step 2: Analyze loop() output

   loop() prints "Looping" every 1000 milliseconds (1 second) repeatedly.

3. Final Answer:

   Start printed once, then Looping printed every second -> Option C

4. Quick Check:

   setup() once, loop() repeats = B [OK]

Hint: setup() prints once, loop() repeats output [OK]

Common Mistakes:

• Thinking loop() runs once
• Missing Serial.begin() call
• Ignoring delay causing fast prints

4. Identify the error in this Arduino code:

void setup() {
  pinMode(13, OUTPUT);
}

void loop() {
  digitalWrite(13, HIGH);
  delay(1000);
  digitalWrite(13, LOW);
  delay(1000)
}

medium

A. Missing semicolon after delay(1000) in loop()

B. pinMode should be in loop(), not setup()

C. digitalWrite cannot be used with pin 13

D. delay() cannot be used inside loop()

Solution

1. Step 1: Check syntax line by line

   In loop(), the line delay(1000) is missing a semicolon at the end.

2. Step 2: Verify other parts

   pinMode is correctly placed in setup(). digitalWrite works with pin 13. delay() is allowed in loop().

3. Final Answer:

   Missing semicolon after delay(1000) in loop() -> Option A

4. Quick Check:

   Syntax error = missing semicolon [OK]

Hint: Check every line ends with a semicolon [OK]

Common Mistakes:

• Placing pinMode in loop() unnecessarily
• Assuming digitalWrite can't use pin 13
• Thinking delay() is disallowed in loop()

5. You want to blink an LED connected to pin 9 exactly 5 times when the Arduino starts, then stop blinking. Which code correctly uses setup() and loop() to do this?

hard

A. Use a counter in setup() to blink 5 times; leave loop() empty

B. Blink 5 times inside loop() without a counter

C. Blink 5 times inside loop() using a counter, then stop blinking

D. Blink 5 times inside setup(), then keep blinking in loop()

Solution

1. Step 1: Understand blinking 5 times only once

   Since blinking 5 times is a one-time task, it should be done in setup() which runs once.

2. Step 2: Keep loop() empty to stop further blinking

   Leaving loop() empty prevents repeated blinking after the initial 5 times.

3. Final Answer:

   Use a counter in setup() to blink 5 times; leave loop() empty -> Option A

4. Quick Check:

   One-time task in setup() = A [OK]

Hint: One-time actions go in setup(), repeated in loop() [OK]

Common Mistakes:

• Blinking in loop() without stopping
• Not using a counter to limit blinks
• Putting one-time code in loop() causing repeats