AH = 05 AL = new page number, see VIDEO PAGES for PCjr only: AL = 80h to read CRT/CPU page registers 81h to set CPU page register BL = CPU page register 82h to set CRT page register BH = CRT page register 83h to set CPU and page registers BH = CRT page register BL = CPU page register on return: (PCjr only) BH = CRT page register BL = CPU page register