led driver

/*
Drive a seven segment display using HCF4511


*/

//Declaration of Arduino pins used as HCF4511 inputs
const int A = 2;
const int B = 3;
const int C = 4;
const int D = 5;

void setup() {
  pinMode(A0, INPUT);
  pinMode(A, OUTPUT); //LSB
  pinMode(B, OUTPUT);
  pinMode(C, OUTPUT);
  pinMode(D, OUTPUT); //MSB

}

int count = 0; //the variable used to show the number

void loop() {
  if (digitalRead(A0) == LOW) //if button is pressed
  {
    count++;
    delay(200); //the delay prevent from button bouncing
    if (count == 10) //we want to count from 0 to 9!
      count = 0;
    to_BCD(); //convert to binary
  }

  if (count == 10)
    count = 0;

}

void to_BCD()
{
  if (count == 0) //write 0000
  {
    digitalWrite(A, LOW);
    digitalWrite(B, LOW);
    digitalWrite(C, LOW);
    digitalWrite(D, LOW);
  }

  if (count == 1) //write 0001
  {
    digitalWrite(A, HIGH);
    digitalWrite(B, LOW);
    digitalWrite(C, LOW);
    digitalWrite(D, LOW);
  }

  if (count == 2) //write 0010
  {
    digitalWrite(A, LOW);
    digitalWrite(B, HIGH);
    digitalWrite(C, LOW);
    digitalWrite(D, LOW);
  }

  if (count == 3) //write 0011
  {
    digitalWrite(A, HIGH);
    digitalWrite(B, HIGH);
    digitalWrite(C, LOW);
    digitalWrite(D, LOW);
  }

  if (count == 4) //write 0100
  {
    digitalWrite(A, LOW);
    digitalWrite(B, LOW);
    digitalWrite(C, HIGH);
    digitalWrite(D, LOW);
  }

  if (count == 5) //write 0101
  {
    digitalWrite(A, HIGH);
    digitalWrite(B, LOW);
    digitalWrite(C, HIGH);
    digitalWrite(D, LOW);
  }

  if (count == 6) //write 0110
  {
    digitalWrite(A, LOW);
    digitalWrite(B, HIGH);
    digitalWrite(C, HIGH);
    digitalWrite(D, LOW);
  }

  if (count == 7) //write 0111
  {
    digitalWrite(A, HIGH);
    digitalWrite(B, HIGH);
    digitalWrite(C, HIGH);
    digitalWrite(D, LOW);
  }

  if (count == 8) //write 1000
  {
    digitalWrite(A, LOW);
    digitalWrite(B, LOW);
    digitalWrite(C, LOW);
    digitalWrite(D, HIGH);
  }

  if (count == 9) //write 1001
  {
    digitalWrite(A, HIGH);
    digitalWrite(B, LOW);
    digitalWrite(C, LOW);
    digitalWrite(D, HIGH);
  }
}