IBMBIO.COM

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IBMBIO.COM is a filename used by the boot loader for several DOS operating systems. It serves the same purpose as IO.SYS in MS-DOS, and it is part of PC-DOS, DR DOS, and earlier versions of MS-DOS.

In the PC bootup sequence, the first sector of the boot disk is loaded into memory and executed. If this is the DOS boot sector, it loads the first three sectors of IBMBIO.COM into memory and transfers control to it. IBMBIO.COM then:

1. Loads the rest of itself into memory.
2. Initializes each default device driver in turn (console, disk, serial port, et cetera). At this point, the default devices are available.
3. Loads the DOS kernel and calls its initialization routine. The kernel is stored in IBMDOS.COM.

[edit] See also

IBMDOS.COM