Just like digital files work in your RAM so do they work in the CMOS of the BIOS.The ROM BIOS containes all of the digital circuits necessary to detect and control the various components of the computer.The BIOS flash file is like a text file that places values or switch positions in the ROM modules.When you flash your BIOS you are recording these settings into the BIOS CMOS.There is also something that is pre BIOS that is the inner workings of the chip itself.The ROM BIOS is really big!It is the virtual transistors that make it possible for DC digital control.