Loops

This video goes over the different types of loops and what they do. Feel free to watch it over and over and over and…

Loops let you repeat parts of our code over again. You can have them repeat for a certain number of times or until something else happens.

One kind of loop is while loops. They’re similar to if statements but instead of running the code once, it will keep looping until the condition you set is false:

while( condition )
{
    // then repeat code
}

While loops can be used with variables to create test programs:

int A = 0;
while( A < 8 )
{
    A = A + 1;
}

What’s going on in the code above:

• A’s initial value is 0.
• 1 will be added to A while A is less than 8.
• Once A is not less than 8, the loop will be exited.
• It only checks after it has finished ALL of the code in the loop!

int A = 0;
while( A < 8 )
{
    A = A + 10;
    A = A - 9;
}

What’s going on in the code above:

• A’s initial value is 0.
• The code adds 10 to A, which would cause A to be greater than 8.
• However, the loop will not stop because 9 is subtracted from A before the code checks to see if A is greater than 8.

This is the pseudocode:

1. Check if A is less than 8
2. Add 10 to A  (A is 10)
3. Subtract 9 from A (A is 1)
4. Check if A is less than 8
5. Add 10 to A  (A is 11)
6. Subtract 9 from A (A is 2)
7. Check if A is less than 8
8. Repeat

Here is a full example program:

int A = 0;

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

void loop() {
    while(A < 5)
    {
    A = A + 1;

    Serial.println("in the while loop");
    delay(100);
    } 
    A = 0; 
    Serial.println("not in the while loop");
    delay(100);
}

This is the pseudocode:

• Set the serial monitor baud rate at 9600.
• Check if the variable, A, is less than 5.
• Add 1 to A (A is 1).
• Print “in the while loop” on the serial monitor.
• Delay 100 milliseconds.
• Repeat until A is greater than 5.
• When A is greater than 5, exit the while loop.
• Set A to 0.
• Print “not in the while loop” on the serial monitor.
• Delay 100 milliseconds.
• Repeat!

The output would look something like this:

• in the while loop
• in the while loop
• in the while loop
• in the while loop
• in the while loop
• not in the while loop
• in the while loop
• in the while loop
• in the while loop
• in the while loop
• in the while loop
• not in the while loop
• etc.

Another type of loop is for loops, which repeat for a specific amount of times. Look at the example below!

for( int i = 0; i < 5; i++)
{
    // code to repeat
}

This for loop has three important parts in its parentheses:

1. The variable keeps track of how many times your code has been looped through. You can name your variable whatever you want, but the standard for for loops is to name it “i”.
2. The condition will repeat as long as everything is still true, just like a while loop. In this case, the condition is if i is less than 5.
3. The last part of the for loop is to add 1 to i. ++ is the same thing as i = i +1. Anything that changes the value of a variable will be done at the end of your loop.

This is the pseudocode:

1. 1. Create i (i is 0)
   2. Check if i is less than 5
   3. Run code
   4. Add 1 to i (i is 1)
   5. Check if i is less than 5
   6. Run code
   7. Add 1 to i (i is 2)
   8. Check if i is less than 5
   9. Repeat

Here’s an example of a full for loop code:

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

void loop() {
    for (int i = 0; i < 5; i++)
    {
    Serial.println(i);
    delay(100);
}

    Serial.println("Out of the for loop");
    delay(100);
}

This is the pseudocode:

• Set the serial monitor’s baud rate at 9600.
• Check if i is less than 5 (i is 0).
• Add 1.
• Print i’s value on the serial monitor (1).
• Delay by 100 milliseconds.
• Repeat until i is greater than 5.
• When i is greater than 5, exit the for loop.
• Print “Out of the for loop” on the serial monitor.
• Delay by 100 milliseconds.

This is what the serial monitor should look like:

• 0
• 1
• 2
• 3
• 4
• Out of the for loop