//Draw black text on the existing text to erase it.
    textout_ex(
             screen,//Specify bitmap on the screen
             font,//Use a default font
             "HELLO WORLD",//Specify the text to display
             x,//x-coordinate for text
             y,//y-coordinate for text
             makecol(0,0,0),//Color text black
             -1 );//Transparent text background.