What is BIOS?
The Basic Input Output System, or BIOS, is the foundation of the personal computer’s operation. It is the program that is executed first when the computer is powered up, and it is used by DOS and other programs to access each piece of hardware inside the computer. The bootup program, however, isn’t the only code in the computer that is called BIOS. In fact, the BIOS that executes when the PC is turned on is typically called the Motherboard BIOS, because it is located on the motherboard. Until recently, this BIOS was fixed in a ROM chip and could not be reprogrammed to fix bugs and enhance the features. Today, the Motherboard BIOS is in an electronically reprogrammable memory chip called Flash EPROM, but it is still the same old BIOS. Anyway, the Motherboard BIOS walks through system memory to find other hardware in the system that also contains code foundational to its use (other BIOS code). For example, your VGA card has its own BIOS physically located on the VGA card itself—it’s usually called the Video BIOS or VGA BIOS. Your hard and floppy disk controller has a BIOS that is also executed at boot time. People often will both refer to these collective programs as the BIOS and refer to a specific individual BIOS as the BIOS. Neither reference is incorrect.
With all that said, you should know that BIOS is not DOS—BIOS is the lowest-level software functionality available on the PC. DOS “sits on top of ” the BIOS and calls the BIOS regularly to perform routine operations that you might mistakenly attribute to being a “DOS” function. For example, you might use DOS function 40 hex to write data to a file on the hard disk. DOS actually performs this task by ultimately calling the hard disk BIOS’s function 03 to actually write the data to the disk.
Cross Reference:
XIV.6: What are interrupts?
No comments:
Post a Comment