//button matrix row / collumn pins
int r1 = 2;
int r2 = 3;
int c1 = 4;
int c2 = 5;
//led pins
int rled = 6;
int gled = 7;
int bled = 8;
int yled = 9;

void setup() {
  // put your setup code here, to run once:
// button settup
pinMode(r1, OUTPUT);
pinMode(r2, OUTPUT);
pinMode(c1, INPUT);
pinMode(c2, INPUT);
// led settup
pinMode(rled, OUTPUT);
pinMode(gled, OUTPUT);
pinMode(bled, OUTPUT);
pinMode(yled, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
digitalWrite(r1, HIGH);      // 1st row
if (digitalRead(c1)) {
  digitalWrite(rled, HIGH);
} else {digitalWrite(rled, LOW);}
if (digitalRead(c2)) {
  digitalWrite(gled, HIGH);
} else {digitalWrite(gled, LOW);}
digitalWrite(r1, LOW);

digitalWrite(r2, HIGH);      // 2nd row
if (digitalRead(c1)) {
  digitalWrite(bled, HIGH);
} else {digitalWrite(bled, LOW);}
if (digitalRead(c2)) {
  digitalWrite(yled, HIGH);
} else {digitalWrite(yled, LOW);}
digitalWrite(r2, LOW);
}