// Code for 3 7-segment displays (approx. 1 second timer)
// Are there better ways to do this?  Yes.

int seg[] = {6, 7, 8, 9, 10, 11, 12};
int sel[] = {3, 4, 5};

int a = 0;
int b = 0;
int c = 0;
int n = 0;

void setup() {
  pinMode(seg[0], OUTPUT);
  pinMode(seg[1], OUTPUT);
  pinMode(seg[2], OUTPUT);
  pinMode(seg[3], OUTPUT);
  pinMode(seg[4], OUTPUT);
  pinMode(seg[5], OUTPUT);
  pinMode(seg[6], OUTPUT);
  pinMode(sel[0], OUTPUT);
  pinMode(sel[1], OUTPUT);
  pinMode(sel[2], OUTPUT);
}

void writeDigit(int pos, int val) {
  digitalWrite(sel[0], (pos==0)?HIGH:LOW);
  digitalWrite(sel[1], (pos==1)?HIGH:LOW);
  digitalWrite(sel[2], (pos==2)?HIGH:LOW);
  digitalWrite(seg[0], (val==0||val==2||val==6||val==8)?LOW:HIGH);
  digitalWrite(seg[1], (val==1||val==4||val==7||val==9)?HIGH:LOW);
  digitalWrite(seg[2], (val==2)?HIGH:LOW);
  digitalWrite(seg[3], (val==5||val==6)?HIGH:LOW);
  digitalWrite(seg[4], (val==1||val==4)?HIGH:LOW);
  digitalWrite(seg[5], (val==1||val==2||val==3||val==7)?HIGH:LOW);
  digitalWrite(seg[6], (val==0||val==1||val==7)?HIGH:LOW);
}

void loop() {
  writeDigit(0, a);
  delay(3);
  writeDigit(1, b);
  delay(3);
  writeDigit(2, c);
  delay(4);
  n++;
  if (n == 100) {
    n = 0;
    c++;
    if (c == 10) { c = 0; b++; }
    if (b == 10) { b = 0; a++; }
    if (a == 10) { a = 0; }
  }
}