From Power-Up to the Main Function

There are three steps from power-up to the main function, and they are designated to load the operating system (OS) from a boot disk and prepare for the main function. The first step is to load the BIOS (Basic Input/Output System), build the interrupt vector table, and start interrupt service routines in real address mode. The second step is to load the OS program from the boot disk into the memory using the interrupt service routines. The third step is to complete any other preparation to run the 32-bit main function. This chapter describes how these three steps work in the computer.