Interaction between the CPU and the human user

The human interfaces to the Application that is running, such as word, excel, calculator, etc. The program is controlled by the operating system. The programs gets access to resources such as printers and CD-rom, by permission from the OS - using software called a "driver". The CPU, in its most native state (such as when a new blank hard drive is installed), uses the BIOS (Basic Input/Output System) to get time/date information and to read the hard and floppy drives.