Discuss BIOS function call with one example.
BIO stands for Basic Input Output System: This is a set of programs to give most basic low-level services as services keyboard, serial port, disks, printer, display and bootstrap. Basic input and output programs are stored in a ROM. While power is switched on ROM-BIOS takes the control of a computer. Initially, ROM-BIOS programs for power-on-self test are executed. These tests check whether the computer is in appropriate working order after such test, the process of loading the operating system in main memory is termed as booting. ROM-BIOS contains a program termed as bootstrap loader, this directs CPU to read with the disk a specific program termed as boot and to load it in main memory.
BIOS function calls are found stored into the system and video BIOS ROMs. This BIOS ROM function directly controls the I/O devices, along with or without DOS loaded in a system.
INT10H: It is a BIOS interrupt is often termed as the video services interrupt since it directly controls the video display into a system. The INT10H instruction uses a register AH to choose video services given by this interrupt. The video BIOS ROM is situated on the video board and varies from one video card to the other.
INT11H: This function used to determine the type of equipment installed into the system.
INT12H: The memory size is returned through the INT 12 H instructions.
INT13H: such call controls the diskettes and also hard or fixed disk drives attached to the system.
INT14H: Such call controls the serial COM ports attached to the computer.