Implement a 4-bit binary counter

How do you plan to solve it?

Initially, create an array of GPIO pins (arrled) of output LED. Assign increment and decrement button as input pullup. Assign initial value of 'value' as 0.

Create a function placeValue() to assign output of ith pin based on ith bit of value.

Initialize all pins. In loop function, check condition of button pressed. If increment button is pressed, increase the value by 1 and if decrement button is pressed, decrement the value by 1. If value is at max (15) or min (0), assign it to 0 or 15 respectively.

Call function placeValue to assign GPIOs based on updated value.

int bit_len = 4;
int arrled[4] = {8,9,10,11};
int inc = 2;
int dec = 3;
int value = 0;

void placeValue(int value){
  for(int i=0; i<bit_len; i++){
    digitalWrite(arrled[i],((value>>i)&1));
  }
  Serial.begin(9600);
}

void setup() {
  // put your setup code here, to run once:
  for(int i=0; i<4; i++){
    pinMode(arrled[i], OUTPUT);
  }
  pinMode(inc, INPUT_PULLUP);
  pinMode(dec, INPUT_PULLUP);
}

void loop() {
  // put your main code here, to run repeatedly:
  
  if(digitalRead(inc) == 0){
    value++;
    if(value==16)
      value = 0;
  }
  if(digitalRead(dec) == 0){
    value--;
    if(value == -1)
      value = 15;
  }
  placeValue(value);
  Serial.println(value);
  delay(150);

}

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