BIOS

Today , every computer has BIOS as connector from hardware to software. We can say the function of BIOS here is very important too such like CPU , Motherboard , Ram , Harddisk Drive in computer system.

Because of that , i think we have to know what is BIOS exactly mean, and for that i have a little explanation about BIOS bellow here .

In computing, the BIOS is an acronym that stands either for the Basic Input/Output System or for Built In Operating System (see Acronym definition). The latter term dates from the late 1970s and early 1980s when the PCs of the day normally contained a comprehensive operating system in their ROMs. The latter acronym is still much used in conjunction with gadgetry containing dedicated computers, such as modern cameras, white-wear, etc. The underlying technology is very similar, being little more than a matter of size.

BIOS refers, in part, to the firmware code (a type of boot loader) run by a PC when first powered on. The primary function of the BIOS is to identify and initialize system component hardware (such as the video display card, hard disk, and floppy disk) and some other hardware devices. This is to prepare the machine into a known low capability state, so other software programs stored on various media can be loaded, executed, and given control of the PC.This process is known as booting, or booting up, which is short for bootstrapping.

The BIOSes of IBM PC class machines are coded programs embedded on a chip that recognize and control various devices that make up x86 personal computers, and provide a small library of basic Input/Output functions that can be called to operate and control the peripherals such as the keyboard, primitive (800 x 600) display functions and so forth.

Computers designed to run Windows ME or Windows 2000, or later, supersede this basic monitor functionality by taking over direct control of the interrupt table and replacing the monitor routines with faster and more robust low-level modules that, unlike the BIOS function set, are re-entrant. Various BIOS functions in ROM were left in control in earlier Windows versions, and the BIOS only comes into play today in the alternate shell Cmd.exe, or if the machine is booted into a legacy DOS version

The term first appeared in the CP/M operating system, describing the part of CP/M loaded during boot time that interfaced directly with the hardware (CP/M machines usually had a simple boot loader in ROM, and nothing else). Most versions of DOS have a file called "IBMBIO.COM" or "IO.SYS" that is analogous to the CP/M disk BIOS. The term was also known as Binary Input/Output System and Basic Integrated Operating System.

Among other classes of computers, the generic terms boot monitor, boot loader or boot ROM were commonly used. Some Sun and Macintosh PowerPC computers used Open Firmware for this purpose. There are a few alternatives for Legacy BIOS in the x86 world: Extensible Firmware Interface, Open Firmware (used on the OLPC XO-1) and corebot.

Prior to the early 1990s, BIOSes were stored in ROM or PROM chips, which could not be altered by users. As its complexity and need for updates grew, and re-programmable parts became more available, BIOS firmware was most commonly stored on EEPROM or flash memory devices. According to Robert Braver, the president of the BIOS manufacturer Micro Firmware, Flash BIOS chips became common around 1995 because the electrically erasable PROM (EEPROM) chips are cheaper and easier to program than standard erasable PROM (EPROM) chips. PROM chips may be erased by prolonged exposure to ultraviolet light, which accessed the chip via the window. Chip manufacturers use PROM blasters to reprogram EPROM chips. EEPROM chips come with the additional feature of allowing a BIOS reprogramming via higher-than-normal amounts of voltage.BIOS versions are upgraded to take advantage of newer versions of hardware and to correct bugs in previous revisions of BIOSes.

The first flash chips attached to the ISA bus. Starting in 1997, the BIOS flash moved to the LPC bus, a functional replacement for ISA, following a new standard implementation known as "firmware hub" (FWH). Most BIOS revisions created in 1995 and nearly all BIOS revisions in 1997 supported the year 2000. In 2006, the first systems supporting a Serial Peripheral Interface (SPI) appeared, and the BIOS flash moved again......... Continue

Data and source mostly taken from Wikipedia.