int i; // counter variable 
int count=0;
int SW1=3;  //Set SW1 to Pin 3
int SW2=4;  //Set SW2 to Pin 4

void setup(){
 DDRB = DDRB | B00001111;    // set direction bits for pins 8 to 10
 
 Serial.begin(9600); 
 pinMode(SW1,INPUT);
 pinMode(SW2,INPUT);
 digitalWrite(SW1, HIGH); //enable pullup. Switch connected to ground
 digitalWrite(SW2, HIGH); //enable pullup. Switch connected to ground
} 

void loop(){ 
  while (digitalRead(SW1)==LOW) // check if COUNT_UP switch is released
  {
    count++;
    if (count>15){  //restart after 7
     count=0;
    }
    // 3 bits manipulated 0 to 7
    PORTB = PORTB & B11110000;  // clear out bits 2 -4, leave pins 0 and 1 untouched (xx & 11 = xx)
    PORTB = PORTB | count;   // combine the port information with the new information for LED pins 
    Serial.print("count=");
    Serial.println(count);
    Serial.print("PORTB in BINary=");
    Serial.println(PORTB, BIN); // debug to show masking 
    delay(200); 

  }
  while (digitalRead(SW2)==LOW) // check if COUNT_DOWN switch is released
  {
    count--;
    if (count<0){  //restart after 7
     count=15;
    }
    // 3 bits manipulated 0 to 7
    PORTB = PORTB & B11110000;  // clear out bits 2 -4, leave pins 0 and 1 untouched (xx & 11 = xx)
    
    PORTB = PORTB | count;   // combine the port information with the new information for LED pins 
    Serial.print("count=");
    Serial.println(count);
    Serial.print("PORTB in BINary=");
    Serial.println(PORTB, BIN); // debug to show masking 
    delay(200); 

  }
  delay(200);
}