Topic       : The ATARI Compendium
Author      : Scott Sanders / JAY Software
Version     : 1.25 (20/6/2003)
Subject     : Documentation
Nodes       : 1117
Index Size  : 32614
HCP-Version : 6
Compiled on : Atari
@charset    : UTF-8
@lang       : en
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@help       : %About
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                                  Atari GEM


AES

The AES is responsible for window and menu control, messaging services, and
object rendering and manipulation.

VDI

The VDI consists of a series of drivers which provide device-independent
access to the display screen and external output devices such as printers
and plotters through GDOS. All graphic primitive operations are accomplished
with the VDI. The AES, for instance, uses the VDI to render its objects
on screen.

GDOS

GDOS is a disk-loadable subsystem of the VDI. The term GDOS can refer to
original GDOS, FONTGDOS, or SpeedoGDOS. It controls loadable device drivers
and fonts. The original GDOS was limited to bitmap fonts and did not have
the bezier capabilities of FONTGDOS or SpeedoGDOS.

FONTGDOS

FONTGDOS is essentially a newer, faster GDOS with bezier rendering functions
present. FONTGDOS is otherwise completely backwardly compatible with GDOS.

SpeedoGDOS

SpeedoGDOS, named for the Speedo™ font format created by Bitstream,
Inc., adds outline font rendering capability to the basic features of
GDOS. SpeedoGDOS also includes a sophisticated caching system to promote
the fastest rendering possible.

Two versions of outline GDOS exist. The original version (referred to as
Font Scaling Module (FSMGDOS) ), based on QMS/Imagen fonts, was never
officially released. Nonetheless, a small number of users still use
FSMGDOS and differences between them are noted.

LINE-A

LINE-A is a special set of routines that provide an assembly language
interface to routines and variables belonging to the VDI and XBIOS. It is
so named because instruction opcodes beginning with the hexadecimal number
$A utilize a special microprocessor exception which point to the LINE-A
routines in ROM.

LINE-A is the only operating system component that has become out of date
and incompatible. Atari recommends that software developers avoid using
LINE-A as it will be supported less and less as hardware advancements make
its use more incompatible. LINE-A is documented briefly in this reference
for completeness.

Desktop

The 'Desktop' is a independent GEM application burned into ROM. It
facilitates program launching and file manipulation as well as providing
a graphical shell for user-interaction.

XCONTROL

XCONTROL (Extensible Control Panel) is a desk accessory application that
provides access to multiple modules called CPX's (Control Panel Extensions)
which are used to control system configuration and other related functions.
A special section in this reference discusses the creation of CPX's and the
utility functions provided by the XCONTROL shell accessory.