Hi, how can program runnig on CPU (mostly OS) acess other PC hardware? Such as Graphic card, HDD and so? From what I read, In DOS, this was done using BIOS calls, specifically INT instruction. But, int instruction should only jump to the certain space in RAM. So, how can some program stored in RAM acess other computer HW, when CPU can acess only RAM, and reeive interrupts? And, does windows use int instructions as well, or is there any new way to communicate with HW? Thanks.