01-09-2012, 12:53 PM
Basic Input Output Service
BIOS_Level_Programming.ppt (Size: 144.5 KB / Downloads: 116)
Contains system data used by the ROM BIOS service routines.
Serves as a standardized communication interface between the computer’s hardware and the operating system.
BIOS
Is a small ROM chip on the PC’s motherboard.
A basic software program containing all BIOS functions is permanently stored in the ROM.
This software functions as a basic operating system.
Is responsible for starting the PC.
This hardware integrated with software is also referred to as firmware.
BIOS History
Intel developed the 8086 and 8088 in the end of the 70s.
IBM decided to make an affordable computer out of the 8088.
Microsoft created the operating system (DOS).
DOS(Disk Operating System) Fundamentals
Consisted of two parts
The BIOS itself is one part of the operating system.
The other part consists of the operating system program files.
Program files consist of
Utilities
A kernel that is loaded into the main memory when the computer boots.
Cloning
IBM introduced the complete PC with the operating system in 1981.
IBM owned copyrights to the BIOS.
IBM published all the assembly language source code for the IBM PC/XT BIOS.
Peter Norton wrote the landmark book Inside the IBM-PC.
Microsoft made DOS available to other licensees.
Clones
Compaq developed a BIOS by 1983. Also introduced their own PC.
Phoenix Technologies released a BIOS package (IBM-compatible BIOS and a version of DOS).
Manufacturers of today, such as AMI, Award and MR-BIOS, all developed their own source code for an IBM-compatible BIOS.
Functions of the BIOS
When you first turn on your PC
Your PC requires information
to detect PC components
To find the operating system(floppy disk, hard drive, or a CD-ROM)
This information is stored in the BIOS
Plug and Play
After all hardware components have been found and checked, Plug and Play goes to work.
Interrupts and DMA channels of the plug-in cards in the ISA and PCI buses are queried and distributed.
Onboard hardware, located on motherboard and in its ISA/PCI slots, are configured for operation.
Bootstrap Loader
BIOS next accesses the first sector of the hard drive, alos termed the boot sector, and starts the “bootstrap loader”
A small program that knows the file structure of the storage medium and can call the operating system’s start routine.
An Interpreter
In old operating systems (DOS 6.2), the BIOS acts as a mediator (or interface) between the hardware and the software.
New operating systems, circumvent the BIOS and communicate directly with the hardware through the appropriate drivers.
Microsoft Kernels
Kernel of a Microsoft operating system consists of
Msdos.sys
Io.sys
MSDOS.sys controls the keyboard input and the screen output.
IO.sys communicates with the BIOS and contains the actual program code of the operating system and a process control for the hardware.