private void button1_Click(object sender, EventArgs e)
        {
            //when button is clicked, open file dialog
            OpenFileDialog ofd = new OpenFileDialog();
            ofd.Filter = "GB ROMs|*.gb";

            // if user selects a file, get the file name and display it in the label get only the name, not the path
            if (ofd.ShowDialog() == DialogResult.OK)
            {
                label1.Text = ofd.SafeFileName;
            }

            // get the map from the pointer
            // pointers are : 0x9800 to 0x9BFF for map 1 and 0x9C00	0x9FFF for map 2

            const int map1 = 0x9800;
            const int map2 = 0x9C00;

            // transform the data into a 2D array and display it in the textbox