Comparing Values

Part of the First Circuits section of Coddy's Arduino journey. Lesson 20 of 22.

A condition compares two values. C++ has six ways:

== is equal to
!= is not equal to
< is less than, > is more than
<= is less than or equal to, >= is more than or equal to

A common mistake is writing = where you mean ==. One = stores a value; two compare.

if (count == 5) { ... }   // is count 5?
if (count = 5) { ... }    // stores 5 in count!

The second line compiles, and it is a trap: it puts 5 into count, and since 5 is not 0, the board treats it as true. The braces run every time, and count is reset to 5 each time round.

Challenge

Easy

The starter counts up every 300 ms and prints each number. Make the LED on pin 13 light on one number only:

if count is equal to 5, turn the LED on
else, turn it off

The LED should light while the monitor shows 5, and stay off for every other number. Press Run, then Check.

Try it yourself

int count = 0;

void setup() {
  pinMode(13, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  count = count + 1;
  Serial.println(count);
  // LED on when count is 5, off otherwise
  delay(300);
}

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 elseComparing ValuesCombining Conditions Read a Button

2Talking to Your Computer

Hello, Serial Monitor Print Versus Println Printing Numbers Your First Variable Counting 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