Millennium Time Capsule/AC2000.BIN/disks/ac10disk/atozbook/g.txt

Text File | 1998-06-10 | 25KB | 586 lines

                             "The Atari A to Z"
                              by Mark S Baines
                      Copyright (c) 1998 Mark S Baines
                             All Rights Reserved


       YOU MUST READ "READ_ME.NOW" BEFORE YOU LOOK AT ANY OF THIS FILE
*****************************************************************************


G


G
Giga


Gate
A control junction of a transistor and a basic logic circuit, such as an AND
gate.


Gateway
A computer that acts as an interface between two different communications
networks often using different communications protocols and thus a convenient
route from one to the other.


GDOS
Graphic Device Operating System. The part of GEM contained as a separate
executable file (e.g. GDOS.PRG). It contains device-independent functions for
font and graphics screen display and printing, allows the creation of
metafiles and provides support for various output devices up to a resolution
of 32,767 x 32,767. It allows graphics to be printed at the highest resolution
of the output device. The program must be in the AUTO folder and loaded at
boot-up where it reads an ASSIGN.SYS file in the root directory which
associates the font names found in this file with a device driver and ID
number. Once this is done, an application can open a physical or virtual
workstation with an appropriate device ID and load in the fonts corresponding
to that ID via a vst_load_font() call. An open physical workstation looks into
each entry of the ASSIGN.SYS information structure for the device ID.

Workstations have different device IDs, which by convention are:

  Table G1: GDOS Devices and ID Numbers

  Device type       Device ID numbers
  Screen (VDI)      01-10  control graphic hardware
  Plotter           11-20  translates graphics to plotter commands
  Printer           21-30  process graphics data for printers
  Metafile          31-40  create vector graphic .GEM files
  Camera            41-50
  Graphics tablet   51-60
  Memory            61-90  create a monochrome image in memory
  IMG               91-99  saves images as an .IMG file

In the VDI, a device ID of 1 is used as the default. On the ST-TT this could
lead to problems depending on what resolution the computer is in. If a
physical workstation was opened with an ID of 1, an application could get
fonts that were designed for medium resolution on a high resolution screen,
for instance. Therefore other IDs are assigned:

  Table G2: GDOS Screen Drivers Devices and Resolution

  Device      Resolution
  ID Number
  01          Default
  02          ST low resolution
  03          ST medium resolution
  04          ST high resolution
  05          Falcon (any resolution)
  06          TT medium resolution
  07
  08          TT high resolution
  09          TT low resolution
  10

The device ID number can be derived from adding two to the returned value from
calling the Getrez() function:

  device_id = Getrez() + 2;

At present, only ten device IDs are catered for.

Only one ASSIGN.SYS file is needed if it contains all the fonts required by
each screen resolution and other device ID, e.g.

  path=c:\gemsys   ; path of folder containing fonts and drivers
  01p screen.sys   ; Default workstation ID number
  02p screen.sys   ; ST low resolution screen driver and fonts
  SLSS10.FNT       ; Swiss screen font 10 point
  SLSS14.FNT
  SLTR10.FNT       ; Times screen font 10 point
  SLTR14.FNT
  03p screen.sys   ; ST medium resolution screen driver and fonts
  SMSS10.FNT
  SMSS14.FNT
  SMTR10.FNT
  SMTR14.FNT
  04p screen.sys   ; ST high resolution screen driver and fonts
  SHSS10.FNT
  SHSS14.FNT
  SHTR10.FNT
  SHTR14.FNT
  08p screen.sys   ; TT high resolution screen driver and fonts
  STHSS10.FNT
  STHSS14.FNT
  STHTR10.FNT
  STHTR14.FNT

The screen aspect ratio for high and low resolution are similar enough for the
same fonts to be used for both of them.

The path= directive must be the first non-comment line in the file. If it is
not, then GDOS will use the current path as the default. The path name must be
no longer than 64 characters long or it will be truncated and not match what
was intended.

There are two mandatory parts to an ASSIGN.SYS file. The workstation ID from
between 0 to 32,767 and the name of the driver file associated with that ID.
In the above typical example, the file screen.sys is the VDI screen driver and
the p following the device ID stands for 'permanent' and means that the driver
is always present at boot-up from the ROM. A r following the device ID
signifies that a driver is to be loaded when GDOS is initialized from the path
contained at the head of the ASSIGN.SYS file. The driver is to remain
'resident' in memory. If none of these two are specified, then the driver is
loaded up when the physical workstation is opened and removed from memory
later.

Comments may be included in the ASSIGN.SYS file and must begin with a
semicolon (;). Anything following this will be ignored.

A file name must be specified for all drivers and if a file name extender is
not specified, then .SYS will be assumed. The last entry in the ASSIGN.SYS
file should not be followed by a new line.

Typically, the ASSIGN.SYS file will contain a list of GDOS bit-mapped printer
fonts which match the relevant screen fonts in a DTP program, for instance.
For this, a printer driver of the type to specifically match the printer in
use has to be defined followed by the list of fonts. The format is the same
format as with the screen fonts above.

  21 printer.sys   ; Printer is LaserJet 4: 600 dpi
  LPSS10.FNT       ; Laser printer Swiss fonts
  LPSS14.FNT
  LPSS20.FNT
  LPSS28.FNT
  LPTR10.FNT       ; Laser printer Times fonts
  LPTR20.FNT
  LPTR14.FNT
  LPTR28.FNT
  22 necp6.sys     ; Alternative 360 dpi printer driver
  NCSS10.FNT       ; 24-pin printer Swiss fonts
  NCSS14.FNT
  NCSS20.FNT
  NCSS28.FNT
  NCTR10.FNT       ; 24-pin printer Swiss fonts
  NCTR20.FNT
  NCTR14.FNT
  NCTR28.FNT
  31r meta.sys     ; Metafile driver
  61r memory.sys   ; Memory driver

Here, two printer drivers have been given device IDs of 21 and 22. The font
files following them are specific to that driver and some programs allow the
driver to be changed so that different printers can be used with the same set
up. Some programs, like Timeworks Publisher v1 requires that the fonts be
listed in the font ID number order. Only special programs, such as Fontkit can
show what these are and allow them to be changed.

The Metafile driver normally is device 31 and is required if metafiles (.GEM
vector image files) are to be created and printed out. The Memory driver
creates a monochrome image of the page to be printed in memory. In addition,
there are image drivers which create an .IMG file instead of sending the data
to a printer.

The best version of GDOS is Release 1.1. A PD replacement written in Germany
called AMCGDOS provides good results. Replacements for GDOS were introduced in
1992. See FONTGDOS, FSMGDOS, SpeedoGDOS, ASSIGN.SYS, EXTEND.SYS.


GDP
Generalized Drawing Primitive. Ten basic drawing functions of the VDI such as
circle, rectangle, arc etc.


GEM
Graphics Environment Manager. A graphics oriented operating system front-end
developed by Digital Research Inc. In 1982, DRI developed the Graphics System
Extension GSX as an extension to its operating systems. In 1984, it introduced
the Virtual Device Interface VDI and by combining these graphical and
operating system technologies with an icon-based graphics environment, GEM was
developed in 1985. It is a true device-independent, WIMP environment
consisting of two major subsystems, the VDI and the AES. These basically
comprise of a library of routines and functions which can be used by programs
to draw windows, handle menus and operate dialog boxes and mouse responses.
GEM allows the same programming routines to be made on different computers
that support it with the end result being the same.

Originally, GEM was an extension to DOS for the PC and a competitor to a
similar environment on the Apple Macintosh. The screen, which looked very
similar to that of a Mac's, was entirely the work of an application called the
GEM Desktop which ran under the GEM interface. Users had the option of running
a GEM application without the aid of the Desktop, but since DRI bundled a free
GEM Desktop with every application, there was no need to. Unlike the
Macintosh, a user could launch DOS applications from the GEM Desktop. Most of
them could be assigned icons, and there was even a "Launch DOS Commands" menu
item. When a DOS application was started, GEM saved the Desktop and, when the
DOS application ended, returned to the Desktop. This was considered much
better than the DOS shells then available, and users were willing to use GEM
despite a lack of applications.

When the Tramiels took over Atari they wanted a new computer based on the new
Motorola 68000 processor and a graphical front end. Jack Tramiel went to
Digital Research and obtained GEM support. GEM was popular at this time, being
packaged with all Amstrad PCs and Apricot also decided to use GEM. However,
Apple bought a lawsuit against DRI charging them with a copyright violation of
the "look and feel of a Macintosh". DRI didn't feel they could afford the risk
of losing the case and substantial amounts of money defending it and came to
an out-of-court agreement. DRI made some changes to GEM, the Desktop and
removed the Trash Can icon. However, this only applied to the PC version of
GEM, Apple seemingly not considering the ST a threat although part of the
agreement between DRI and Apple meant that development work on GEM ceased for
the Atari range.


GEM.CNF
An ASCII text configuration file loaded at boot-up and processed by the AES
when running under MultiTOS. It is used to set some AES system and environment
variables and to execute GEM programs.

The AES variable names must be in upper case and no spaces are allowed between
them, the '=' character and the following values.

  Table G3: AES System Variables in the GEM.CNF File

  Variable        Meaning
  AE_FONTID=<n>   ID of the font to be used as the system font (default is 1),
                  e.g. AE_FONTID=1
  AE_PNTSIZE=<n>  Point size of font to be used as system font (default is
                  13), e.g. AE_PNTSIZE=13
  AE_SREDRAW=<n>  AES redraws screen before a program launch (default is 1 =
                  yes, 0 = no), e.g. AE_SREDRAW=1
  AE_TREDRAW=<n>  AES redraws screen after program exit (default is 1 = yes, 0
                  = no), e.g. AE_TREDRAW=1
  AE_LANG=<n>     Language used in Desktop (0 = English, 1 = German, 2 =
                  French, 4 = Spanish, 5 = Italian), e.g. AE_LANG=0
  SHELL=<path>    Launch an alternative Desktop or CLI shell,
                  e.g. SHELL=c:\neodesk\neoload.prg

Command names must be in lower case with a single space between the command
and the following value.

There are only two commands. run <path> which will execute a program, such as
run c:\utils\uis_iii.prg. The command setenv name=val is used to set
environment variables such as those you might otherwise have installed in an
alternative Desktop, AUTO folder program or CPX module. Examples might be:

  setenv USER=msbaines
  setenv CLIPBRD=C:\CLIPBRD

GEM.CNF also contains some specific environment variables which can be
installed in MINT.CNF instead, although they are best configured in GEM.CNF.
They are preceded with the command setenv.

  Table G4: AES Environment Variables in the GEM.CNF File

  Variable        Meaning
  ACCEXT=<list>   Comma-separated list of extensions to be recognized as
                  accessories,
                  e.g. setenv ACCEXT=ACC,ACX
  ACCPATH=<paths> Comma-separated list of folders to locate accessories. The
                  boot device root is always searched,
                  e.g. setenv ACCPATH=C:\,C:\ACC
  TOSEXT=<list>   Comma-separated list of extensions to be recognized as TOS
                  programs,
                  e.g. setenv TOSEXT=TOS,TTP
  GEMEXT=<list>   Comma-separated list of extensions to be recognized as GEM
                  programs,
                  e.g. setenv GEMEXT=PRG,PRX,APP,GTP,NPG
  TOSRUN=<path>   Path of TOS handler program, running TOS programs in a
                  windowed shell,
                  e.g. setenv TOSRUN=C:\MULTITOS\MINIWIN.APP
  SHPRINT=<path>  Program run by Desktop to print files,
                  e.g. setenv SHPRINT=C:\MULTITOS\LPR.APP
  SHSHOW=<path>   Program run by Desktop to show files,
                  e.g. setenv SHSHOW=D:\EVEREST\EVEREST.PRG
  DESKCOPY=<path> Program run by Desktop for file copies, moves and renames,
                  e.g. setenv DESKCOPY=C:\UTILS\KOBOLD.PRG
  DESKFMT=<path>  Programs run by Desktop to format and copy disks,
                  e.g. setenv DESKFMT=C:\UTILS\FORMAT.PRG
  PATH=<paths>    Comma-separated list of folders to search for resources for
                  executed programs,
                  e.g. setenv PATH=,C:\MULTITOS,C:\,C:\UTILS


GEM Desktop
The main screen of the Atari TOS/GEM range of computers containing the menu
bar, disk icons and a trash can icon. Onto this, directory windows can be
opened to perform disk housekeeping functions or to launch programs. The
NewDesk Desktop introduced with TOS 2 and 3 contains more icons, such as
printer and program icons.


GEMDOS
Graphics Environment Manager Disk Operating System. That part of TOS which is
the hardware independent part of GEM. It consists of very similar functions to
those of MS-DOS where even the function numbers are the same. Not all the MS-
DOS functions are used, in the area of file management; only the UNIX
compatible ones are implemented and those in MS-DOS that were retained for
compatibility with CP/M are missing, as are those that specifically refer to
Intel chip functions. GEMDOS calls (as well as the BIOS and XBIOS) have the
function number and the parameters placed on the stack and not passed in the
registers as with MS-DOS. GEMDOS calls are made with a TRAP #1 exception.
GEMDOS functions are concerned with disk management, memory allocation and
process management facilities traditionally available in any operating system.
It has to be noted that of all the functions available under TOS as a whole,
this is the most bugged and/or troublesome section although that has improved
with new TOS versions.

GEMDOS functions have a consistent set of prefixes for their naming:

  Table G5: GEMDOS Function Name Prefixes

  Prefix   Meaning
  C        Direct console, printer and auxiliary I/O e.g. Cconin()
  D        Directory and disk management e.g. Dgetpath()
  F        File management and manipulation e.g. Fopen()
  M        Memory management e.g. Malloc()
  P        Process creation and termination e.g. Pexec()
  S        System inquiry and manipulation e.g. Super()
  T        Time and date functions e.g. Tgetdate()


GEMDOS errors
GEMDOS will occasionally return non-fatal and non-processor exception error
messages from a program to the Desktop or other shell program. They may appear
in an alert box or written to the screen. See BIOS errors.

  Table G6: GEMDOS Errors

  Name            No   Meaning
  EOK              0   Operation was successful, no error
  EINVFN         -32   Invalid function number
  EFILNF         -33   File not found
  EPTHNF         -34   Path not found
  ENHNDL         -35   Too many files open (no more handles left)
  EACCDN         -36   Access denied
  EIHNDL         -37   Invalid handle number
  ENSMEM         -39   Insufficient memory
  EIMBA          -40   Invalid memory block address
  EDRIVE         -46   Invalid drive specification
  ENSAME/EXDEV   -48   Cross device rename (not the same drive)
  ENMFIL         -49   No more files
  ELOCKED        -58   Record is locked - (file locking and network)
  ENSLOCK        -59   No such lock (unlock an unlocked record)
  E_RANGE        -64   Range error
  ENAMETOOLONG   -64   Range error (file name component too long)
  EINTRN         -65   Internal error
  EPLFMT         -66   Invalid program load format
  EGSBF          -67   Setblock failure due to growth restrictions
  EBREAK         -68   KAOS: CTRL-C user break
  EXCPT          -69   KAOS: 68000 exception
  EPTHOV         -70   Path overflow
  ELOOP          -80   Too many symbolic links
  EMOUNT        -200   Mount point crossed (indicator)
  ELINK         -300   Data is symbolic link


GEM metafile
A file with a .GEM file name extender containing vector graphics data produced
by an object-oriented drawing program, such as Easydraw. The file is
resolution independent and therefore capable of being printed on any device at
its highest output. The file also has the advantage of taking up far less
storage space than an equivalent bitmapped file. See Drawing program, Bitmap
image.


GEMSYS
Traditionally, the name of the folder where GEM GDOS fonts are stored.


General-purpose language
A programming language that can be used for a variety of purposes, such as
PL/1.


Generate
To produce program object code or machine code from source code, the act of a
compiler, for instance. Also, to produce a string from a macro.


Generation
A term used to indicate the technological state of development of computers.
Current computers are of the 'third generation'. Also, the relation of a file
in a hierarchy of files, each one being updated from the previous one. Three
generations are normally maintained, being the 'grandfather', 'father' and
'son'. At each update the grandfather files are replaced by the new son files,
the other two sets becoming a generation older.


Genlock
The ability of one video source to be time coincident with another. This
synchronization allows a computer video image to be freely mixed with a TV
broadcast video image. All STs had the ability to synchronize their video
output with an external source. This is controlled by bit 0 at $00FF820A.
However, to do this reliably, the system clock must also be phase-locked with
the input sync signals. No way to do this was provided in the ST which meant
that the only Genlock devices available are internal modifications. The STE
allows Genlocking by grounding pin 3 (GPO) on the monitor connector and then
injecting the clock signal into pin 4 (Mono Detect). The internal frequency of
this clock is 32.215905 MHz for NTSC and 32.084988 MHz for PAL systems. On the
Falcon, pin 14 VSYNC, can be programmed as in input (when pin 16 External Sync
Enable is held high) where a low-level will hold the vertical timing generator
in a rest condition. This is typically used by external Genlocking devices.
HSYNC cannot be programmed as an input but horizontal locking is achieved with
a phase locked loop controlling the external video clock in pin 15. An
external video source can drive a clock input into this pin synchronous with
the external video dot clock. The Falcon will use this signal as a master
video clock when selected in software. The maximum frequency this input can be
driven is 32 MHz.


Get
To obtain or fetch a data item from memory or other storage.


Ghost outline
An outline of an icon, file name or window used to show its current position
as it is dragged to a new location on the Desktop.


GIF
Graphics Interchange Format. A bitmap graphics format from CompuServe which
aims to maintain the correct colours of on-screen images when transferred
between different computers. Such files have the .GIF file name extender.


Giga - G
A billion (one thousand million) or 10^9.


Gigabyte
A thousand million bytes which in computing is 2^30 or 1,073,741,824 bytes or
1,024 megabytes.


GIGO
Garbage In Garbage Out. Term used to emphasize the fact that a computer can
only produce good results from good (accurate) inputs.


GIOS
Graphic Input/Output System. GEM's input/output system containing all the
device-specific input and output functions for devices connected to the ST-
Falcon range. It is the interface between GDOS and the other devices, such as
printers and the screen.


Global
With respect to the total rather than to a part. Also, in programming, a
variable or function defined in one section of a program and available to any
other function and holding its value throughout execution.


GLUE
The Atari custom chip that 'glues' all the others together on the ST. It
usually comes in a 68-pin PLCC package like the MMU. It generates the 2 MHz
timing frequency for the PSG chip and 500 kHz for the keyboard and MIDI
interface from an 8 MHz clock signal, the interrupt signal, the Bus Error
signal, HSYNC, VSYNC, BLANK and DE video signals and it decodes the address
range taking in the 23 address lines. On the STE and TT the GLUE and MMU chips
were amalgamated into a single MCU chip. See MCU.


Glytch
On disks and tape, where the magnetization pattern of one track crosses over
onto another making the reading of the data difficult. Sometimes wrongly used
to describe an error or bug.


Gopher
A menu-based system for searching for information and resources through the
Internet. It differs from WWW in not being hypertext-based. The term is
derived from the phrase 'go for' and was developed at the University of
Minnesota, the Gopher State. See Internet, WAIS, WWW.


Golf ball printer
A printer using a small sphere with characters embossed on it which when
pressed against a ribbon prints the character onto paper. Effectively replaced
by the daisywheel.


Grabbing
The action of selecting an icon in a WIMP system and moving it to another
location. Under GEM, point at an icon, press and hold the left mouse button
and move it or 'drag' it to another location. The act of selecting an icon is
'grabbing' whilst its movement across the screen is 'dragging'.


Grandfather
A term applied to the second update of a file. See Generation.


Graph
A two-dimensional representation of numeric values consisting of lines or
curves superimposed on a grid.


Graphic
A meaningful two-dimensional representation of elements such as lines and dots
as printed on a display device, e.g. a character, picture, icon.


Graunch
Term applied to a hardware failure (originally a disk head crash).


Greeking
A method of representing text on screen, typically in a DTP program, by a
series of horizontal lines or other pattern when a font is too small to be
displayed properly at the screen's low resolution.


Grid
A series of parallel perpendicular intersecting lines to which screen objects
can be snapped into place for accurate alignment, such as in a DTP frame, CAD,
drawing or painting program.


Ground
The connection of circuit elements in an AC mains system to earth.


Group
A number of items present together or considered as a unit.


GSX
Graphics System Extension. An early developmental project of Digital Research
into graphics system software which was considered an extension to their
operating systems. It was combined with the VDI to form the basis of GEM in
1985. See GEM.


GTP
Gem Takes Parameters. The file extension for GEM programs that can accept
command parameters before being launched in the same way as .TTP programs.


Guard band
On magnetizable disks, a group of unused tracks that mark the inner and outer
limits of the recordable surface.


Guard tone
A band of unused frequencies (usually 550 Hz) used to separate adjacent speech
or data bands in a frequency-division multiplexed system.


Guard zone
A length of track on a magnetic disk that is left unrecorded between two
adjacent sectors to ensure that data is never overwritten because of
inaccuracies in the alignment of the read/write heads and the positioning of
the sector marks.


GUI
Graphic User Interface. An operating system front-end that is graphics-based
allowing the user to control the computer through icons and a mouse. The aim
behind GUIs is to make the use of the computer intuitive to the user without
the steep learning process of struggling with command words and parameters
when using a command line interface. This development has been taken further
with WIMP environments. GUIs, such as Windows on the PC are not necessarily
full WIMP environments like GEM and that on the Mac.


Gulp
A group of several bytes.


G
44 entries
EOF