Loop with condition

#include <TimerOne.h>
//the pins of 4-digit 7-segment display attach to pin2-13 respectively
int a = 2;
int b = 3;
int c = 4;
int d = 5;
int e = 6;
int f = 7;
int g = 8;
int machine = 9;

int d4 = 10;
int d3 = 11;
int d2 = 12;
int d1 = 13;

long n = 0;// n represents the value displayed on the LED display. For example, when n=0, 0000 is displayed. The maximum value is 9999.
long m = 0;
int x = 100;
int y = 60;

int del = 5;//Set del as 5; the value is the degree of fine tuning for the clock
int count = 0;//Set count=0. Here count is a count value that increases by 1 every 0.1 second, which means 1 second is counted when the value is 10
int seconds = 0, minutes = 0, hours = 0;

void setup()
{
  pinMode(d1, OUTPUT);
  pinMode(d2, OUTPUT);
  pinMode(d3, OUTPUT);
  pinMode(d4, OUTPUT);
  pinMode(a, OUTPUT);
  pinMode(b, OUTPUT);
  pinMode(c, OUTPUT);
  pinMode(d, OUTPUT);
  pinMode(e, OUTPUT);
  pinMode(f, OUTPUT);
  pinMode(g, OUTPUT);
  pinMode(machine, INPUT);


  Timer1.initialize(100000); // set a timer of length 100000 microseconds (or 0.1 sec - or 10Hz => the led will blink 5 times, 5 cycles of on-and-off, per second)
  Timer1.attachInterrupt( add ); // attach the service routine here
}

void loop()
{
  int digit_value_1;
  int digit_value_2;
  int digit_value_3;
  int digit_value_4; 
  if (digitalRead(machine) == HIGH)
  {
    // 1. Load number 1

    digit_value_1 = seconds % 10;
    digit_value_2 = (seconds / 10) % 10;

    // 2. Load number 2

    digit_value_3 = (minutes) % 10;
    digit_value_4 = (minutes / 10) % 10;
    }

    //3. Update number to display
    pickDigit(0);//Light up 7-segment display d1
    pickNumber(digit_value_1);// get the value of thousand
    delay(del);//delay 5ms

    pickDigit(1);//Light up 7-segment display d2
    pickNumber(digit_value_2);// get the value of hundred
    delay(del);//delay 5ms

    pickDigit(2);//Light up 7-segment display d3
    pickNumber(digit_value_3);//get the value of ten
    delay(del);//delay 5ms

    pickDigit(3);//Light up 7-segment display d4
    pickNumber(digit_value_4);//Get the value of single digit
    delay(del);//delay 5ms

    delay(1);//loop delay update every 1 ms
}

void pickDigit(int x) //light up a 7-segment display
{
  switch (x)
  {
    case 0:
      digitalWrite(d1, HIGH); digitalWrite(d2, LOW); digitalWrite(d3, LOW); digitalWrite(d4, LOW);
      break;
    case 1:
      digitalWrite(d1, LOW); digitalWrite(d2, HIGH); digitalWrite(d3, LOW); digitalWrite(d4, LOW);
      break;
    case 2:
      digitalWrite(d1, LOW); digitalWrite(d2, LOW); digitalWrite(d3, HIGH); digitalWrite(d4, LOW);
      break;

    case 3:
      digitalWrite(d1, LOW); digitalWrite(d2, LOW); digitalWrite(d3, LOW); digitalWrite(d4, HIGH);
      break;

    default:
      digitalWrite(d1, LOW); digitalWrite(d2, LOW); digitalWrite(d3, LOW); digitalWrite(d4, LOW);
      break;
  }
}

void pickNumber(int x)
{
  switch (x)
  {
    case 0:
      zero();
      break;
    case 1:
      one();
      break;
    case 2:
      two();
      break;
    case 3:
      three();
      break;
    case 4:
      four();
      break;
    case 5:
      five();
      break;
    case 6:
      six();
      break;
    case 7:
      seven();
      break;
    case 8:
      eight();
      break;
    case 9:
      nine();
      break;
    default:
      zero();
      break;
  }
}

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

void zero() //display 0
{
  digitalWrite(a, LOW);
  digitalWrite(b, LOW);
  digitalWrite(c, LOW);
  digitalWrite(d, LOW);
  digitalWrite(e, LOW);
  digitalWrite(f, LOW);
  digitalWrite(g, HIGH);
}

void one() //display 1
{
  digitalWrite(a, HIGH);
  digitalWrite(b, LOW);
  digitalWrite(c, LOW);
  digitalWrite(d, HIGH);
  digitalWrite(e, HIGH);
  digitalWrite(f, HIGH);
  digitalWrite(g, HIGH);;
}

void two() //display 2
{
  digitalWrite(a, LOW);
  digitalWrite(b, LOW);
  digitalWrite(c, HIGH);
  digitalWrite(d, LOW);
  digitalWrite(e, LOW);
  digitalWrite(f, HIGH);
  digitalWrite(g, LOW);
}
void three() //display 3
{
  digitalWrite(a, LOW);
  digitalWrite(b, LOW);
  digitalWrite(c, LOW);
  digitalWrite(d, LOW);
  digitalWrite(e, HIGH);
  digitalWrite(f, HIGH);
  digitalWrite(g, LOW);
}

void four() //display 4
{
  digitalWrite(a, HIGH);
  digitalWrite(b, LOW);
  digitalWrite(c, LOW);
  digitalWrite(d, HIGH);
  digitalWrite(e, HIGH);
  digitalWrite(f, LOW);
  digitalWrite(g, LOW);
}

void five() //display 5
{
  digitalWrite(a, LOW);
  digitalWrite(b, HIGH);
  digitalWrite(c, LOW);
  digitalWrite(d, LOW);
  digitalWrite(e, HIGH);
  digitalWrite(f, LOW);
  digitalWrite(g, LOW);
}

void six() //display 6
{
  digitalWrite(a, LOW);
  digitalWrite(b, HIGH);
  digitalWrite(c, LOW);
  digitalWrite(d, LOW);
  digitalWrite(e, LOW);
  digitalWrite(f, LOW);
  digitalWrite(g, LOW);
}

void seven() //display 7
{
  digitalWrite(a, LOW);
  digitalWrite(b, LOW);
  digitalWrite(c, LOW);
  digitalWrite(d, HIGH);
  digitalWrite(e, HIGH);
  digitalWrite(f, HIGH);
  digitalWrite(g, HIGH);
}

void eight() //display 8
{
  digitalWrite(a, LOW);
  digitalWrite(b, LOW);
  digitalWrite(c, LOW);
  digitalWrite(d, LOW);
  digitalWrite(e, LOW);
  digitalWrite(f, LOW);
  digitalWrite(g, LOW);
}

void nine() //display 9
{
  digitalWrite(a, LOW);
  digitalWrite(b, LOW);
  digitalWrite(c, LOW);
  digitalWrite(d, LOW);
  digitalWrite(e, HIGH);
  digitalWrite(f, LOW);
  digitalWrite(g, LOW);
}

void add()
{
  if (count < 10)
  {

    count ++;
  }

  else
  {
    count = 0;
    if (seconds < 59) seconds++;

    else
    {
      seconds = 0;
      if (minutes < 59)minutes++;

      else
      {
        minutes = 0;
        if (hours < 23)hours++;
        else hours = 0;
      }
    }
  }

}