Conditions

To let the program make decisions, we can use the if statement.

The if statement lets us check if an expression is true or false, and execute code based on the result. Here's an example...

int a = 1;

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

void loop() {
  Serial.println(a);
  if (a == 10) {
    Serial.println("Bang!");
  }
  a = a + 1;
  delay(1000);
}

if (a == 10) : This checks if a is equal to 10. When making a comparison, we use double equal == (Single equal = is used when assigning a value). If the expression is true, the Arduino will run the code inside the curly brackets.

else

We can also tell the Arduino to execute a different set of code if the expression is false...

int a = 1;

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

void loop() {
  Serial.println(a);
  if (a == 10) {
    Serial.println("Bang!");
  } else {
    Serial.println("Whizz...");
  }
  a = a + 1;
  delay(1000);
}

else if

We can also use else if to make multiple comparisons...

int a = 1;

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

void loop() {
  Serial.println(a);
  if (a == 10) {
    Serial.println("Bang!");
  } else if (a == 9) {
    Serial.println("Almost there.");
  } else {
    Serial.println("Whizz...");
  }
  a = a + 1;
  delay(1000);
}

Comparison Expressions

There are multiple types of expressions that we can use...

Combining Expressions

Two or more expressions can also be evaluated together using the && (AND) and || (OR) operators.

Exercise

Add conditions to the below program, so that it displays "Low" if the value of a is less than 10, "High" if the value of a is greater than 10, and "Correct" if it is exactly 10.

int a = 1;

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

void loop() {
  Serial.println(a);

  // Write your code here.
  // Don't change the other lines.

  a = a + 1;
  delay(1000);
}