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The BIOS as Driver for DOS

One of the original functions of the BIOS was as an interface between the OS (DOS, in those days) and the PC's low-level hardware. The idea was simple: Future versions of the PC might use different low-level hardware than that in the original PC, so if the OS called BIOS routines to access hardware, the OS would not need to be rewritten for every minor hardware variant in existence. Because most non-DOS OSs are 32-bit, though, they can't use the BIOS in this way—or, to be more precise, they can, but only at the cost of serious performance degradation. Instead, modern OSs use drivers—special low-level programs that access hardware on behalf of the OS. Fortunately, most hardware components for which the BIOS was written use fairly standardized designs, so few specialized drivers are required to get an OS functioning at least minimally. As time has gone on, though, more and more new devices have been invented, such as CD-ROM drives, small computer system interface (SCSI) host adapters, scanners, and so on. Each of these items requires a special driver, often even in DOS.

The end result is that one of the BIOS's original functions is of little importance with most modern OSs. This does not mean that you can do away with the BIOS, however, because it serves other vital functions.

 

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