LedMatrix.h

#ifndef LEDMATRIX_H
#define LEDMATRIX_H

#include "Arduino.h"

class LedMatrix {
	int _rows[8];
	int _cols[8];

public:
	LedMatrix(int rows[], int cols[]) {
		for(int i=0; i<8; i++) {
			_rows[i] = rows[i];
			_cols[i] = cols[i];
		}
	}

	void begin() {
		for(int i=0; i<8; i++) {
			pinMode(_rows[i], OUTPUT);
			pinMode(_cols[i], OUTPUT);
		}
	}

	// displays a single (row, column) "pixel"
	// 0 indexed
	// assumes the screen was just cleared
	void display(int row, int column) {
		digitalWrite(_rows[row], LOW);
		digitalWrite(_cols[column], HIGH);
		for(int i=0; i<8; i++) {
			if(i != column) digitalWrite(_cols[i], LOW);
		}
	}

	void clear() {
		for(int i=0; i<8; i++) {
			digitalWrite(_rows[i], HIGH);
			digitalWrite(_cols[i], HIGH);
		}
	}
};

#endif

main.cpp

// as connected on https://www.arduino.cc/en/Tutorial/BuiltInExamples/RowColumnScanning
int rows[] = { 2, 7, A5, 5, 13, A4, 12, A2 };
int cols[] = { 6, 11, 10, 3, A3, 4, 8, 9 };

LedMatrix matrix(rows, cols);

void setup() {
	matrix.begin();
}

void loop() {
	matrix.clear();
	matrix.display(3, 5);
	delay(500);
}