Working with 7-Segment Display

const int A = 2;
const int B = 3;
const int C = 4;
const int D = 5;
const int E = 6;
const int F = 7;
const int G = 8;
const int DP = 9;

void setup()
{
  pinMode (A, OUTPUT);
  pinMode (B, OUTPUT);
  pinMode (C, OUTPUT);
  pinMode (D, OUTPUT);
  pinMode (E, OUTPUT);
  pinMode (F, OUTPUT);
  pinMode (G, OUTPUT);
  pinMode (DP, OUTPUT);
}

void loop()
{
  zero();
  delay (1000);
  one();
  delay (1000);
  two();
  delay (1000);
  three();
  delay (1000);
  four();
  delay (1000);
  five();
  delay (1000);
  six();
  delay (1000);
  seven();
  delay (1000);
  eight();
  delay (1000);
  nine();
  delay (1000);
}

void zero()
{
  digitalWrite (A, LOW);
  digitalWrite (B, LOW);
  digitalWrite (C, LOW);
  digitalWrite (D, LOW);
  digitalWrite (E, LOW);
  digitalWrite (F, LOW);
  digitalWrite (G, HIGH);
  digitalWrite (DP, HIGH);
}

void one()
{
  digitalWrite (A, HIGH);
  digitalWrite (B, LOW);
  digitalWrite (C, LOW);
  digitalWrite (D, HIGH);
  digitalWrite (E, HIGH);
  digitalWrite (F, HIGH);
  digitalWrite (G, HIGH);
  digitalWrite (DP, HIGH);
}

void two()
{
  digitalWrite (A, LOW);
  digitalWrite (B, LOW);
  digitalWrite (C, HIGH);
  digitalWrite (D, LOW);
  digitalWrite (E, LOW);
  digitalWrite (F, HIGH);
  digitalWrite (G, LOW);
  digitalWrite (DP, HIGH);
}

void three()
{
  digitalWrite (A, LOW);
  digitalWrite (B, LOW);
  digitalWrite (C, LOW);
  digitalWrite (D, LOW);
  digitalWrite (E, HIGH);
  digitalWrite (F, HIGH);
  digitalWrite (G, LOW);
  digitalWrite (DP, HIGH);
}

void four()
{
  digitalWrite (A, HIGH);
  digitalWrite (B, LOW);
  digitalWrite (C, LOW);
  digitalWrite (D, HIGH);
  digitalWrite (E, HIGH);
  digitalWrite (F, LOW);
  digitalWrite (G, LOW);
  digitalWrite (DP, HIGH);
}

void five()
{
  digitalWrite (A, LOW);
  digitalWrite (B, HIGH);
  digitalWrite (C, LOW);
  digitalWrite (D, LOW);
  digitalWrite (E, HIGH);
  digitalWrite (F, LOW);
  digitalWrite (G, LOW);
  digitalWrite (DP, HIGH);
}

void six()
{
  digitalWrite (A, LOW);
  digitalWrite (B, HIGH);
  digitalWrite (C, LOW);
  digitalWrite (D, LOW);
  digitalWrite (E, LOW);
  digitalWrite (F, LOW);
  digitalWrite (G, LOW);
  digitalWrite (DP, HIGH);
}

void seven()
{
  digitalWrite (A, LOW);
  digitalWrite (B, LOW);
  digitalWrite (C, LOW);
  digitalWrite (D, HIGH);
  digitalWrite (E, HIGH);
  digitalWrite (F, HIGH);
  digitalWrite (G, HIGH);
  digitalWrite (DP, HIGH);
}

void eight()
{
  digitalWrite (A, LOW);
  digitalWrite (B, LOW);
  digitalWrite (C, LOW);
  digitalWrite (D, LOW);
  digitalWrite (E, LOW);
  digitalWrite (F, LOW);
  digitalWrite (G, LOW);
  digitalWrite (DP, HIGH);
}

void nine()
{
  digitalWrite (A, LOW);
  digitalWrite (B, LOW);
  digitalWrite (C, LOW);
  digitalWrite (D, LOW);
  digitalWrite (E, HIGH);
  digitalWrite (F, LOW);
  digitalWrite (G, LOW);
  digitalWrite (DP, HIGH);
}