The BIOS system (Basic Input/Output System), more precisely its successor UEFI (Unified Extensible Firmware Interface) is located on the motherboard (MoBo) of a computer. It retains the data stored on it, even if no electricity is supplied. It reads the actual operating system and allows some presettings regarding the hardware resources. For example, you can optimise the central processing unit (CPU). The most common procedure is to select the data medium from which the desired operating system is to be booted. In addition, the UEFI can be used to activate or deactivate peripheral devices and to adjust the direct memory access (DMA).

CPU

IO-CPU-RAM

DMA

IO-DMA-RAM

The UEFI setup programme can be called up directly after switching on the computer with one of the function buttons F1, F2, F8, F10, F12, Del or Esc. Depending on the manufacturer, the assignment of the key for calling the setup program varies; the correct function key is shown briefly when the computer is switched on.