int a = 6; 
int b = 7; 
int c = 9; 
int d = 2; 
int e = 3; 
int f = 5; 
int g = 4; 
int dp = 8; 
int BUTTON = 10;

void setup() {
  pinMode(BUTTON, INPUT);
  pinMode(a, OUTPUT);
  pinMode(b, OUTPUT);
  pinMode(c, OUTPUT);
  pinMode(d, OUTPUT);
  pinMode(e, OUTPUT);
  pinMode(f, OUTPUT);
  pinMode(g, OUTPUT);
  pinMode(dp, OUTPUT);

  displayTest();
  clearDisplay();
}

void loop() {
  int BUTTONstate = digitalRead(BUTTON);
  if(BUTTONstate == LOW) 
  {
    displayE();  
  } else {
    clearDisplay();
  }
  delay(50);
}

void displayTest(void)
{
  clearDisplay();
  delay(500);
  displayAll();  
  delay(500);
  clearDisplay();
}

void displayE(void) 
{
  digitalWrite(a,HIGH);
  digitalWrite(f,HIGH);
  digitalWrite(g,HIGH);
  digitalWrite(e,HIGH);
  digitalWrite(d,HIGH);
} 

void clearDisplay(void) 
{ 
  digitalWrite(a,LOW);
  digitalWrite(b,LOW);
  digitalWrite(g,LOW);
  digitalWrite(c,LOW);
  digitalWrite(d,LOW);  
  digitalWrite(e,LOW);  
  digitalWrite(f,LOW);  
  digitalWrite(dp,LOW);  
}

void displayAll(void) 
{ 
  digitalWrite(a,HIGH);
  digitalWrite(b,HIGH);
  digitalWrite(g,HIGH);
  digitalWrite(c,HIGH);
  digitalWrite(d,HIGH);  
  digitalWrite(e,HIGH);  
  digitalWrite(f,HIGH);  
  digitalWrite(dp,HIGH);  
}