using an if statement to display binary numbers

if_statement.ino

int led1 = 9;
int led2 = 10;
int led4 = 11;
int led8 = 12;
//...etc

void setup() {
  pinMode(led1, OUTPUT);
  pinMode(led2, OUTPUT);
  //...etc
}

void loop() {
  displayNumber(4);
  //Try this!! (comment out the line above, uncomment the line below)
  // displayNumber(millis()/1000); //millis() is a function that returns the number of milliseconds since the program started (powered on the arduino, reset, or uploaded code)

  //what happens? Why?
}

//this is a better way of doing the number display. 
//read this:
// http://www.toptechboy.com/arduino/lesson-14-if-statements-and-conditionals-in-arduino/
// and this about if and if-else loops. Or ask your dad how they work!
// https://learn.sparkfun.com/tutorials/digital-sandbox-arduino-companion/7-if-this-then-that
//it is still an additional FUNCTION, but this time we can give it an ARGUEMENT in the parenthasees like so. 
//and when we CALL it in the loop FUNCTION above, it will PASS that ARGUEMENT into the FUNCTION and it will
//become the VARIABLE 'n'. 
//try encorporating this code into your code. and using this if statement to display numbers instead.

void displayNumber(int n) {
  if(n == 0) {
    digitalWrite(led1, 0);
    digitalWrite(led2, 0);
    digitalWrite(led4, 0);
    digitalWrite(led8, 0);
  } else if(n == 1) {
    digitalWrite(led1, 1);
    digitalWrite(led2, 0);
    digitalWrite(led4, 0);
    digitalWrite(led8, 0);
  } else if(n == 2) {
    digitalWrite(led1, 0);
    digitalWrite(led2, 1);
    digitalWrite(led4, 0);
    digitalWrite(led8, 0);
  }
  //...etc
}


// This is how it was....
// .....


// void one() {
//   digitalWrite(led1, 1);
//   digitalWrite(led2, 0);
//   digitalWrite(led4, 0);
//   digitalWrite(led8, 0);
// }
// 
// void two() {
//   //...etc
// }