Conditionals

If you would like an explanation on if statements, watch this video. Else, move on to the steps below or another lesson.

If statements let our code make decisions. We use them all the time in our lives! For example:

• If it is sunny, I will go outside.
• If I am thirsty, I will drink some water.
• If my cat is clawing me, then I will stop pulling on its tail.

if (condition)
{
    //then action
}

The condition (inside of the parentheses) is the “if” part, and inside of the curly braces is the “then” part. The first part of one of our examples would look like this:

if (it is sunny)
{
    //then I will go outside
}

Now that you know what an if statement is, you can write an actual program using variables and if statements. Create variable A with a value of 12 and an if statement to see if it’s larger than 10. If it is, variable A will be set to 10.

int A = 12; if (A > 10){    
    A = 10}

Now you can add an else statement, which will be performed if the if statement turns out to be false:

if (condition)
{
    //happens if condition is true
}
else
{
    //happens if condition is false
}

Create an else statement so A will be set to 1 if it is not larger than 10. Your code should look like this:

int A = 12;
if (A > 10)
{
    A = 10;
}
else
{
    A = 1;
}

You can combine everything together into an else if statement:

int A = 3;

if (A > 10)
{
    A = 10;
}
else if (A < 5)
{
    A = 1;
}
else
{
    A = 9;
}

The pseudocode, or the description of what the computer is reading, is:

• If A is greater than 10 it will equal 10.
• If A is not greater than 10 and less than 5, it will equal 1.
• If A is not greater than 10 and not less than 5, it will equal 9

For these conditions you have several comparison options using mathematical symbols:

• Greater than: >
• Less than: <
• Greater than or equal to: >=
• Less than or equal to: <=
• Equal to: ==
• Not equal to: !=

Create your own code, or try this one out:

int A = 1; // create A

void setup() {
    Serial.begin(9600); // starts the serial monitor
}
 
void loop() {
    // prints out the value of A
    Serial.print("A = ");
    Serial.println(A);

    if( A > 10) // if A is greater than 10
    {
        A = 0; // set A to 0
    }
    else if( A == 1) // otherwise if A equals 1
    {
        A = 3; // set A to 3
    }
    else // otherwise
    {
    A = A + 1; // add one to A
    }

    delay(100);
}

When you run this code on the serial monitor, it should output:

• A = 1
• A = 3
• A = 4
• A = 5
• A = 6
• A = 7
• A = 8
• A = 9
• A = 10
• A = 11
• A = 0
• A = 1
• A = 3
• A = 4
• etc.

Since A is set to 1, the computer will go to the else if part and add 1. A will then become 3. 1 will keep being added to A until A is greater than 10. Once that happens, A will be set to 0 and the cycle will be repeated.