What is a BIOS file?BIOS is the shortcut for Basic Input/Output System - B, I, O, S - that's where the name comes from! Most computers have a BIOS in ROM (Read Only Memory), or in Flash ROM. Unlike for CD ROMs and cartridges, this memory is built-in, and it cannot be removed from the computer. The computer also gas other built-in memory: RAM. But, RAM does 'forget' its content when the computer is switched off. Only ROM can memorize data and program code even when it is off! In fact, a BIOS ROM really contains such program code, and never forgets it!
The program code is used to boot the computer every time when it is switched on. What does that mean? It means that it initializes the computer, and, after initialization it will usually search for attached disk drives or cartridges, and then tries to load the actual operating system (Windows is an example) or, in case of gaming consoles, it loads a game (for example: Super Mario!).
But that is not all. Many BIOSes also include functions which can be used to Input/Output data to or from the hardware! The operating system and games can use these functions to access the hardware, for example, to write text on the screen, or even to read or write data from any attached disk drives!
Special thanks to: http://nocash.emubase.de/gbabios.htm