Neon-komputadór

BIOS (Basic Input/Output System)

Although it seems to be distant and far too deeply embedded for user concerns, some understanding of a computer's BIOS is essential concept to understanding the computer as a whole. It really is the link between the hardware and software of a system and includes a very important component which most users have had some experience with - device drivers. What confuses people is that the core of the BIOS is a nonvolatile ROM component on the motherboard, but this isn't all of what it consists of. BIOS, a general term, includes all drivers in a system that act as an interface between the hardware and the software in the system. It includes the motherboard BIOS, BIOS ROM on adapter cards, and BIOS loaded into the computer's memory from disk (device drivers).

If one things of a computer in a series of layers (and we'll return to this conceptual model in the next chapter) the following is illustrative. The key features to understand is that applications talk to operating systems via an Application Program Interface, operating systems talk to hardware via BIOS and device drivers. Whilst the interaction between the operating system and the BIOS is the same, the connection between the BIOS and the hardware differs (as different machines have different hardware).

The BIOS on the motherboard contains the device drives for the most basic components of the system; the keyboard, the floppy drive, the hard disk drive, the input/output ports and so forth. Obviously, most of these become operational soon after the computer is turned on. The same applies for some adapter card BIOS ROM, such as video adaptors, SCSI adaptors, Network adaptors, and IDE expansion adaptors.

BIOS is related to, but distinct from, the CMOS RAM in a computer system. The latter is a Real-Time Clock/Non-Volatile Memory chip made from CMOS (complementary metal-oxide semiconductor). Basically, it's a very low power chip that runs on a battery in the system (that should last about five years) rather than the power supply.