Your First Variable

Part of the First Circuits section of Coddy's Arduino journey. Lesson 10 of 22.

A variable is a named box that holds a value. This line makes one:

int waitTime = 300;

int is the type: the box holds a whole number (an integer). waitTime is its name, and 300 is the value put in it. You can then write the name wherever you would write the number:

delay(waitTime);   // waits 300 ms

Change the value in one place, and every line that uses the name follows.

Make the variable at the top of the sketch, above setup(). A variable made inside setup() only exists inside setup(), so loop() could not use it.

A name is made of letters, digits and _, with no spaces, and upper and lower case count: waitTime and waittime are two different names. Serial.println(waitTime) prints the value, 300; Serial.println("waitTime") prints the word.

Challenge

Easy

Blink the LED on pin 13 with a variable:

at the top, make int waitTime = 300;
use waitTime in both delay() calls
in setup(), print the value of waitTime

Press Run, then Check. Try changing 300 to another number and run it again.

Try it yourself

// make the variable here

void setup() {
  pinMode(13, OUTPUT);
  Serial.begin(9600);
  // print the variable
}

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

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

All lessons in First Circuits

1Hello, Board

Blink an LED Setup and Loop Change the Blink Speed An LED of Your Own Two LEDs Taking Turns Comments in Your Sketch

4Decisions

Decisions with if Choosing with if and else Comparing Values Combining Conditions Read a Button

2Talking to Your Computer

Hello, Serial Monitor Print Versus Println Printing NumbersYour First VariableCounting Up When an Int Runs Out

3Math on the Board

Named Constants Arithmetic Operators Integer Division Decimals with float A Blink That Speeds Up

Practice on your own: Arduino playground