b'CODE TO NOTETo declare a standard input, use the line INTERNAL PULL-UPpinMode(pin, INPUT);. If you would like to use RESISTOR: one of the RedBoards built-in pull-up 20k resistors, it would look like this:pinMode(pin, INPUT_ pinMode(pin, INPUT_PULLUP);. The advantage PULLUP); of external pull-ups is being able to choose a more exact value for the resistor.DIGITAL INPUT: Check to see if an input pin is reading HIGH (5V) or LOW (0V). Returns TRUE (1) or FALSE (0) digitalRead(pin); depending on the reading.This is another logical operator. The is equal to IS EQUAL TO: symbol == can be confusing. Two equals signs are the same as asking, Are these two values equal to one if(digitalRead(pin) ==another? Contrarily, one equals sign means assigning LOW) a particular value to a variable. Dont forget to add the second equals sign if you are comparing two values.CODING CHALLENGESCHANGE THE KEY OF EACH BUTTON: Use the frequency table in the comment section at the end of the code to change the notes that each button plays.PLAY MORE THAN THREE NOTES WITH IF STATEMENTS: By using combinations of buttons, you can play up to seven notes of the scale. You can do this in a few ways. To get more practice with if statements, try adding seven if statements and using the Boolean AND&&operator to represent all of the combinations of keys.PLAY MORE THAN THREE NOTES WITH BINARY MATH: You can use a clever math equation to play more than three notes with your three keys. By multiplying each key by a different number, then adding up all of these numbers, you can make a math equation that produces a different number for each combination of keys.45 : circuit 2b'