Counting Up

Part of the First Circuits section of Coddy's Arduino journey. Lesson 11 of 22.

A variable can change while the sketch runs. This line adds 1 to count:

count = count + 1;

Read it right to left: take what is in count, add 1, and store the result back in count. In C++, = means "store", not "is equal to". count++; is a short way to write the same thing.

Writing count + 1; on its own works out the sum and throws it away: nothing is stored.

Where you make the variable matters. Made at the top, it keeps its value from one loop() to the next. Made inside loop(), it is made again, starting from 0, every time loop() starts.

int count = 0;   // at the top: made once

void loop() {
  count = count + 1;
  Serial.println(count);   // 1, then 2, then 3...
}

Challenge

Easy

Make the board count:

at the top, make int count = 0;
in loop(), add 1 to count, print it, then wait 500 ms

The Serial monitor should show 1, 2, 3 and so on, two numbers a second. Press Run, then Check.

Try it yourself

// make count here

void setup() {
  Serial.begin(9600);
}

void loop() {
  // add 1 to count, print it, wait 500 ms
}

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 Numbers Your First VariableCounting UpWhen 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