INT 15 - BIOS(Basic Input/Output System) A set of standardized calls giving low-level access to the hardware. The BIOS is the lowest software layer above the actual hardware and serves to insulate programs (and operating systems) which use it from the details of accessing the hardware directly. - JOYSTICK SUPPORT (XTIBM PC XT after 1982/11/8,ATIBM PC AT,XT286IBM PC XT/286,PSIBM PS/2, any model) AH = 84h DX = subfunction 0000h read joystick switches Return: AL bits 7-4 = switch settings 0001h read positions of joysticks Return: AX = X position of joystick A BX = Y position of joystick A CX = X position of joystick B DX = Y position of joystick B Return: CF set on error AH = status (see #00496) CF clear if successful Notes: if no game port is installed, subfunction 0000h returns AL=00h (all switches open) and subfunction 0001h returns AX=BX=CX=DX=0000h a 250kOhm joystick typically returns 0000h-01A0h SeeAlso: AH=84h"V20-XT-BIOS"