Atari ST series

CHAPTER 1
gram, (which provides the desktop
metaphor for working with the disk
filing system). The VDI and GEM AES
were subjects of earlier books in this
series by the same author. These
books are also available from COM
PUTE! Books.
BIOS The Basic Input/Output System (BIOS)
is a collection of low-level I/O routines
that are not necessarily specific to the
ST hardware. They include routines to
communicate with character-oriented
devices like the keyboard, screen, and
printer, and to communicate with disk
drives on the sector level. They also
include routines to check which disk
drives are available, if a disk has been
removed from the drive, and so on.
XBIOS XBIOS, the extended Basic Input/Out
put System is a set of hardware-spe
cific I/O-related routines. There are
routines for finding and changing the
address of screen display memory, for
setting the hardware color registers,
for waiting for the vertical blanking
interval, and for accessing the sound
chip. There are also routines for com
municating with the 68901 Multi-Func
tion Peripheral (MFP) chip.
GEMDOS (or BDOS) This is a set of functions used to im
plement the higher level disk filing
system, which closely follows the
model of MS-DOS. These routines al
low the user to access the disk device
on the file level, rather than directly
reading specific physical sectors on
the disk. They allow the user to per
form functions like reading the disk
directory, creating or deleting a subdi
rectory, deleting a file, renaming a
file, and so on. The GEMDOS also
contains miscellaneous routines for
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