Determine the BIOS function with one illustration

BIOS stands for Basic Input Output System. It is a set of programs to provide most basic low-level services like services keyboard, serial port, disks, display, printer and bootstrap. BIOS programs are stored in a ROM. When power is switched on ROM-BIOS takes over the control of a computer. Initially ROM-BIOS programs for power-on-self test are executed. These tests check that whether computer is in proper working order after this test, process of loading the operating system into main memory is known as booting. ROM-BIOS comprises a program known as bootstrap loader, this directs CPU to read from the disk a specific program termed as boot and to load it into main memory.

BIOS function calls are found stored in system and video BIOS ROMs. These BIOS ROM function directly control I/O devices, without or with DOS loaded into a system.

INT10H: This is a BIOS interrupt is often known as video services interrupt as it directly controls the video display in a system. INT10H instruction uses a register AH to select video services provided by this interrupt. Video BIOS ROM is located on the video board and varies from one video card to another.

 INT11H: This function used to determine the type of equipment installed in system.

 INT12H:Memory size is returned by INT 12 H instructions.

 INT13H: This call controls diskettes and also fixed or hard disk drives attached to system.

 INT14H: This call controls the serial COM ports attached to computer.