int r1 = 4;
int r2 = 3;
int r3 = 2;

int c1 = 5;
int c2 = 6;
int c3 = 7;

void setup() {
  // put your setup code here, to run once:
pinMode(r1, OUTPUT);
pinMode(r2, OUTPUT);
pinMode(r3, OUTPUT);

pinMode(c1, INPUT);
pinMode(c2, INPUT);
pinMode(c3, INPUT);

Serial.begin(9600);
}

void loop() {
  // put your main code here, to run repeatedly:
digitalWrite(r1, HIGH); //send 5v to row1
if(digitalRead(c1) == HIGH){  //check collumn1 for input
  Serial.println("btn1");
}
if(digitalRead(c2) == HIGH){  //check collum2 for input
  Serial.println("btn2");
}
if(digitalRead(c3) == HIGH){  //check collumn3 for input
  Serial.println("btn3");
}
digitalWrite(r1, LOW);  //closes the row1 voltage

digitalWrite(r2, HIGH); //send 5v to row2
if(digitalRead(c1) == HIGH){  //check collumn1 for input
  Serial.println("btn4");
}
if(digitalRead(c2) == HIGH){  //check collum2 for input
  Serial.println("btn5");
}
if(digitalRead(c3) == HIGH){  //check collumn3 for input
  Serial.println("btn6");
}
digitalWrite(r2, LOW);  //closes the row2 voltage

digitalWrite(r3, HIGH); //send 5v to row3
if(digitalRead(c1) == HIGH){  //check collumn1 for input
  Serial.println("btn7");
}
if(digitalRead(c2) == HIGH){  //check collum2 for input
  Serial.println("btn8");
}
if(digitalRead(c3) == HIGH){  //check collumn3 for input
  Serial.println("btn9");
}
digitalWrite(r3, LOW);  //closes the row3 voltage
}