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Article #97 (145 is last):
Newsgroups: freenet.sci.comp.atari.library
From: aa399 (Len Stys)
Subject: INFO: GDOS
Date: Mon Jul  2 16:25:59 1990








              EVERYTHING YOU EVER WANTED TO KNOW ABOUT GDOS (AND MORE)

                                by Douglas N. Wheeler


          WHAT IS GDOS?

               GDOS is  an extension  to GEM which adds new capabilities to
          your ST.  GDOS is available with many  commercial Atari programs,
          as well  as to  registered Atari  developers ($500 if it is to be
          distributed with a  product,  free  if  it  is  not  going  to be
          distributed).
          The three primary new capabilities are:

               1.  The ability to use multiple fonts in various point sizes
          on the screen, printer, and other output devices.

               2.  Allows the creation of metafiles, which are standardized
          files intended to be usable by many different applications.  This
          allows files created in one program to be used in another.

               3.  Support for various output  devices with  resolutions up
          to 32,767 x 32,767 (including emulation of this resolution on the
          screen).  This allows  graphics  to  be  printed  at  the highest
          resolution of the output device.


          HOW TO USE GDOS

               In theory,  using GDOS  is as  simple as putting GDOS.PRG in
          your AUTO folder and booting the computer.   In practice, though,
          a series  of conditions must be met.  The most important of these
          conditions is that there must be a valid  ASSIGN.SYS file present
          in the root directory of the boot disk.
               The following is a typical ASSIGN.SYS file.

          PATH=C:\GDOS.SYS
          ;
          01p SCREEN.SYS  ; default screen
          ;
          02p SCREEN.SYS  ; low resolution
          ATSS10.FNT      ; fonts
          ATSS12.FNT
          ATSS18.FNT
          ATSS24.FNT
          ATTP10.FNT
          ATTR10.FNT
          ATTR12.FNT
          ATTR18.FNT
          ATTR24.FNT
          ;
          03p SCREEN.SYS  ; medium resolution
          ATSS10CG.FNT
          ATSS12CG.FNT





          ATSS18CG.FNT
          ATSS24CG.FNT
          ATTP10CG.FNT
          ATTR10CG.FNT
          ATTR12CG.FNT
          ATTR18CG.FNT
          ATTR24CG.FNT
          ;
          04p SCREEN.SYS  ; high resolution
          ATSS10.FNT
          ATSS12.FNT
          ATSS18.FNT
          ATSS24.FNT
          ATTP10.FNT
          ATTR10.FNT
          ATTR12.FNT
          ATTR18.FNT
          ATTR24.FNT
          ;
          21 FX80.SYS  ; Epson 9-pin dot-matrix printer
          ATSS10EP.FNT
          ATSS12EP.FNT
          ATSS18EP.FNT
          ATSS24EP.FNT
          ATTP10EP.FNT
          ATTR10EP.FNT
          ATTR12EP.FNT
          ATTR18EP.FNT
          ATTR24EP.FNT
          ;
          31r META.SYS  ; metafile driver
          ATSS10MF.FNT
          ATSS12MF.FNT
          ATSS18MF.FNT
          ATSS24MF.FNT
          ATTP10MF.FNT
          ATTR10MF.FNT
          ATTR12MF.FNT
          ATTR18MF.FNT
          ATTR24MF.FNT

               As  you  can  see,  I  have  divided  the file into distinct
          groups.  The first line of  the ASSIGN.SYS  file is  used to tell
          GDOS where  the fonts  and device drivers are located.  This line
          must always start with PATH= which is followed  by a  pathname of
          up to 64 characters locating the fonts and drivers.
               Following the  path identifying  line is  the list of device
          drivers and their associated  fonts.   Each group  is composed of
          four parts.  First if a number representing the type of device:

               01-10  Screen drivers
               11-20  Plotter drivers
               21-30  Printer drivers
               31-40  Metafile drivers





               41-50  Camera drivers
               51-60  Tablet drivers

          The Atari STs have four built-in device drivers, they are:

               01   Default screen  (used when  an application doesn't care
          about the screen resolution)
               02  Low resolution screen
               03  Medium resolution screen
               04  High resolution screen

               Immediately following the device number may be a "load flag"
          of either  "p" or "r".  A "p" indicates that the device driver is
          "p"ermanent and does not need to be loaded by GDOS.   Because the
          ST has  it's screen  drivers built  into ROM, there will be a "p"
          after devices  01-04.   An "r"  indicates that  the device driver
          should be kept "r"esident, causing GDOS to load the device driver
          immediately and hold it  in  memory.    If  a  load  flag  is not
          present,  GDOS   will  only   load  the  device  driver  when  an
          application opens (accesses) that device.
               After the device number and load flag is the filename of the
          device driver  as it  appears in the disk directory.  In the case
          of ROM-resident drivers, the filename is only a place-holder (but
          must be present).  Keep in mind that the device driver must be in
          the folder specified in the path line.
               On the lines following those three items is a list  of fonts
          associated with  that device  (again, these  are the filenames as
          they appear in the indicated path of the disk).
               You may have noticed a  few  lines  with  semicolons  (;) in
          them.   GDOS will  treat any  text on  a line  to the  right of a
          semicolon as a comment and will ignore it.
               Some ASSIGN.SYS files have  a  device  00  (00p SCREEN.SYS).
          This  can  help  prevent  incompatibilities between GDOS and some
          older (pre-GDOS) programs.  On the  other hand,  including it can
          cause other  problems.   It is  suggested you leave it out unless
          absolutely necessary.


          EDITING/CREATING ASSIGN.SYS

               Now, why would you  want  to  change  your  ASSIGN.SYS file?
          Well, if  you have  just one program which uses GDOS, and you are
          happy with the fonts you have, then there is no  reason to change
          it.   But, now  that GDOS is beginning to be used more on the ST,
          many of us are  acquiring a  collection of  GDOS applications and
          fonts.  By editing or creating a new ASSIGN.SYS, you could create
          a "universal" ASSIGN.SYS and font/driver folder  to be  used with
          all of these programs!
               Luckily, the ASSIGN.SYS file is a standard text (ASCII) file
          which may be edited with most  text editors  and word processors.
          The  only  requirement  is  that  the  file  does not contain any
          formatting codes.   This  can usually  be accomplished  in a word
          processor  by  turning  document  mode off, or selecting "Save as
          text" (check  your word  processor manual  for exact instructions





          for  doing  this).    If  you  are  using  a text editor, such as
          MicroEmacs or  Tempus,  there  shouldn't  be  any  special saving
          techniques.
               Starting at  the top, the first thing you may want to change
          is the PATH= line at the  beginning of  the ASSIGN.SYS  file.  By
          changing this line, you can put your fonts and printer drivers on
          another disk or hard drive partition (instead of your boot disk).
          If  you  are  using  floppies,  keep  in mind that this directory
          (folder) must be present when an application accesses  any of the
          GDOS devices.   Also,  to speed booting, this directory should be
          present when GDOS is loaded.
               Below is a list  of my  recommended configurations  based on
          what arrangement of disk drives is being used.

               One floppy drive:
                    Boot disk (drive A) with:
                         AUTO folder containing GDOS.PRG
                         GDOS.SYS folder containing the fonts and drivers
                         ASSIGN.SYS with PATH=A:\GDOS.SYS
                         Any  GDOS  application(s)  (you may wish to create
                              separate   boot   disks    for    each   GDOS
                              application)

               Two floppy drives:
                    Boot disk (drive A) with:
                         AUTO folder containing GDOS.PRG
                         ASSIGN.SYS with PATH=B:\GDOS.SYS
                    Font/driver disk (drive B) with:
                         GDOS.SYS folder containing fonts and drivers
                    Application disk (drive A after booting GDOS) with:
                         Any  GDOS  application(s)  (you may wish to create
                              separate  application  disks  for  each  GDOS
                              application)

               Hard drive (booting from floppy):
                    Boot disk (drive A) with:
                         AUTO folder containing hard drive boot program and
                              GDOS.PRG
                         ASSIGN.SYS with PATH=C:\GDOS.SYS
                    Hard drive partition C with:
                         GDOS.SYS folder containing fonts and drivers
                    Any hard drive partition with:
                         Any GDOS application(s) (may be on any partition)

               Hard drive (autobooting):
                    Hard drive partition C with:
                         AUTO folder containing GDOS.PRG
                         GDOS.SYS folder containing fonts and drivers
                         ASSIGN.SYS with PATH=C:\GDOS.SYS
                    Any hard drive partition with:
                         Any GDOS application(s) (may be on any partition)

               Of  course,   these   are   only   suggestions,   and  other
          configurations   may   be   better  for  different  applications.





          Hopefully you should now be able to create  other set-ups without
          too much  difficulty.   There are  a few  "musts" that have to be
          observed:
               1.   GDOS.PRG must be in the AUTO folder of the boot disk.
               2.   ASSIGN.SYS must be in  the root  directory of  the boot
          disk.
               3.   The PATH=  line in the ASSIGN.SYS file must contain the
          complete pathname of the folder containing the fonts  and drivers
          (GDOS.SYS  is  Atari's  current name for this folder--previously,
          Atari called it GEMSYS.  You may, of course, choose  any name you
          like).
               4.   The fonts  and drivers  must be in the right place when
          an application tries to open a device.

               Adding a new device driver or new fonts is very simple.  All
          you  have  to  do  is  put  the device driver and/or fonts in the
          correct folder (as defined  by PATH=)  then add  the filenames to
          the ASSIGN.SYS file.


          A BIT ABOUT FONTS

               One question  about GDOS fonts that people ask is, "when are
          the fonts loaded?"  Many people are under the impression that all
          the fonts  are loaded when GDOS is initially loaded.  This is not
          true (and cannot be done).   An "r"  load flag  in the ASSIGN.SYS
          file  will  cause  GDOS  to  load only the device driver, not the
          fonts.  Fonts are loaded only after an application opens a device
          and asks  for the  fonts to  be loaded.   At that time, GDOS will
          attempt to load all the fonts for that  device.   If there  is an
          error (can't  find the  find, not  enough memory, etc.) GDOS will
          skip over  that font  and continue  with the  next one.   When an
          application is  through with the fonts, it can "unload" the fonts
          to free up that memory.
               Another fact that many people don't  understand is  that the
          font filename  is irrelevant   to GDOS.  Each font has a "header"
          consisting of various parameters, some of these are:  point size,
          font name,  and a  font ID which is used to identify fonts of the
          same type (i.e. all swiss fonts have the same ID).  Another thing
          to  note  is  that  GDOS  does  not  handle line spacing, this is
          handled by  the application  regardless of  the actual  size of a
          given font.   Some  programs use the point size to determine line
          spacing, and others use the actual height of  the font  (yes, the
          point size can be set different from the actual size).
               For  those  of  you  creating  your  own fonts (with GEMFED,
          FONTZ!, or any other way), you must assign a unique font ID (from
          0 to 32,767) to each of your fonts, and all font of the same type
          (i.e. Times), but of different size, must have the same  ID.  You
          should also  note that  some GDOS applications can only use fonts
          with an ID between 0 and 255.  Because of  this, it  is advisable
          to keep your font IDs in that range.
               Another thing you must know when creating your own fonts, is
          the resolution  of the  devices you  are creating  the fonts for.
          The  following  is  a  list  of  most  of the currently available





          devices and their resolution.

               Low resolution screen    45 x 45 (horizontal  dpi x vertical
          dpi)
               Medium resolution screen  91 x 45
               High resolution screen  91 x 91
               9-pin dot-matrix printer  120 x 144
               24-pin printer  180 x 180 or 360 x 360 (NEC P-series only)
               Laser printer  150 x 150 (some) or 300 x 300

               (dpi figures for the screen are approximate)

               As you  can see,  most of  these devices have square (round)
          pixels.  This allows for sideways  printing using  the same fonts
          as for  vertical (normal)  printing.  A notable exception to this
          is  with  the  9-pin  dot-matrix  printers,  which  will  distort
          characters when printing them sideways.  Different drivers handle
          this  differently,  they  either  ignore  the   fact  (and  print
          distorted characters  sideways), or they print the left and right
          sides of a horizontal page on two separate  vertical pages, which
          must then be taped together.  The first method is the easier (and
          faster) of the two,  but the  second method  will produce correct
          characters,  and  the  taping  isn't  too bad if you are going to
          photocopy the final product.
               It would be possible to create  separate fonts  for sideways
          printing. but  so far  this has  not been done.  Also, some Epson
          printers have a 144 x 144  dpi mode  (double plotter  mode) which
          could  be  utilized.    This  would  not only allow non-distorted
          sideways printing, but offers  slight  higher  resolution  in the
          horizontal axis.


          FONT FILENAMES

               As I  stated earlier,  font filenames  are not used by GDOS.
          To us humans, though,  consistent filenames  can greatly simplify
          things.   With the  official release  of GDOS  (late 1987), Atari
          adopted a standardized way  of naming  font files.   Here  I will
          explain Atari's idea and add a few extensions.
               A font  filename like  ATSS10EP.FNT may  look meaningless to
          someone who doesn't know how the filename was derived, but is, in
          fact, very functional.
               The   first   and   second  characters  (AT)  indicates  the
          creator/distributor of the font (in this case Atari).   Atari has
          suggested that these characters be "AT" for all fonts used on the
          Atari; this seems meaningless to me,  as I  don't have  any fonts
          for any  other computers  on my  ST disks (why would I?).  I feel
          these two characters can be put  to  better  use  to  specify the
          creator or distributor of the font.
               The third  and fourth characters (SS) identify the typestyle
          (in  this  case  sans  serif).    These  should  be  unique  to a
          particular rendition of a typeface.
               The fifth  and sixth  characters (10) specify the point size
          of the font.  This should  be the  point size  as printed  on the





          device the  font was  designed for,  not the pixel height.  Also,
          sizes less than 10  should  have  a  leading  zero  (i.e.  06) to
          maintain the overall structure.
               The seventh  and eighth  characters (EP)  specify the device
          for which the font  was designed  (in this  case the  Epson 9-pin
          driver).  If there are no seventh and eighth characters, the font
          is assumed to be for the high-resolution screen.
               The filename extender on all fonts will be .FNT.
               Although not  many companies/individuals  have produced GDOS
          fonts  for  the  ST  (yet),  I  recommend that all font filenames
          follow this convention to avoid confusion.  I also suggest  a few
          standard identifiers:

          Creator/distributor:
               AT - Atari
               MG - Migraph*
               TW - Timeworks*
               NC - Neocept*

          Typestyles:
               SS - Sans Serif (Atari's Swiss)
               TR - Times Roman (Atari's Dutch)
               TP - Typewriter (Atari)
               DB - Dingbats (Timeworks' Bullets)*
               DL - Drury Lane (Timeworks)*
               MA - Madison (Timeworks)*
               RK - Rockface (Timeworks)*
               RA - Ravinia (Timeworks)*
               CL - Camelot (Neocept)*

          Device:
               (none) - Monochrome graphics (high/low resolution screen)
               CG - Color graphics (medium resolution screen)
               EP - Epson 9-pin dot-matrix printer (120 x 144)
               SP - Star NB-15 24-pin dot-matrix printer (180 x 180)
               LB - Atari SMM804 9-pin dot-matrix printer (120 x 144)
               LS - Standard laser printer (300 x 300)
               MF - Metafile
               MG - Monochrome graphics (high/low resolution)*
               NC - NEC P-series 24-pin dot-matrix printer (360 x 360)*
               LL - Low resolution laser printer (150 x 150)*
               LQ - Epson LQ-series 24-pin printers (180 x 180)*

               * indicates unofficial representations which I suggest in an
          effort to standardize font filenames, and  to simplify  the whole
          matter.

               In many  cases, the creator/distributor is not important, in
          which  case  the  first  four  characters  can  be  used  for the
          typestyle.   You will  also notice  that I have listed typestyles
          from various companies, I have done this because I recommend that
          you rename  all of the font you currently have to match the above
          conventions, this will save you a lot of confusion in  the future
          when you  may have ten times as many fonts.  One thing to note if





          you  create  a  master  ASSIGN.SYS  file,  is  that  although the
          Timeworks Swiss  and Dutch fonts are different from Atari's, they
          use the same font IDs.  GDOS could get very confused if  you have
          two  fonts  with  the  same  ID  and  point  size.    My personal
          recommendation is to replace Timeworks' Swiss and Dutch  fonts in
          the 10, 12, 18, and 24 point sizes with the ones from Atari, as I
          feel these are much  more professional  and true  to the original
          Helvetica and Times Roman typefaces.
               Because the  font filename convention has changed since GDOS
          was first made available, it is  helpful to  know the  old format
          (which  is  still  being  used  in  many  cases).    The old font
          filenames were laid out as follows:

               cccrttpp.FNT

               ccc  -    Creator/distributor (for screen fonts,  i.e. MIG =
          Migraph)  or  Device  (for  other  fonts,  i.e. EPS = Epson 9-pin
          printer)
               r    -    Resolution (i.e. L = low res, H=high res)
               tt   -    Typeface (i.e. SS = sans serif, as above)
               pp   -    Point size (as above)


          METAFILES

               Metafiles are theoretically ideal graphics files (keeping in
          mind that text is represented graphically) which can be exchanged
          between different GDOS applications.   Metafiles  are those files
          with a  .GEM extender.  Metafiles are "ideal" in the respect that
          they are  resolution independent.   They  are simply instructions
          for the  computer to recreate a page on any output device at that
          device's highest resolution.   This  is  accomplished  by storing
          commands  for  drawing  lines,  circles,  rectangles, text, etc.,
          unlike most picture files (.NEO, PI?, etc.) which  store the dots
          making up an image.
               Unfortunately,  the  metafile  standard  is  not  being used
          consistently yet.   This  results in  programs not  being able to
          read metafiles  created by  another application.   In most cases,
          the fault lies with the program trying to load the  metafile, not
          the creator.   Many  different parameters  may be  present in the
          header of a metafile, but only a few of these are required.
               Many applications expect (and  need)  some  of  the optional
          parameters to  be present  to properly  represent the  image.  As
          such, they have difficulty loading files  which don't  have these
          parameters.    Currently  Easy-Draw  (version  2.3)  is  the most
          capable of the available GDOS  applications,  and  can  read just
          about any metafile.
               Some of  the more  recent GDOS applications are allowing the
          use of GEM  image  files  (those  ending  in  .IMG).    These are
          bit-mapped  images  similar  to  those  created by the various ST
          paint  programs  (but  without  the  screen  size  and resolution
          limitations).    As  is  the  case  with other paint files, these
          images may be jagged or blocky when printed on a  high resolution
          device.





               A very  important fact about images in metafiles is that the
          metafile does not actually contain a  copy  of  the  image.   The
          metafile only  contains the  filename of the image on disk.  This
          means that you must not remove the disk containing an image while
          the  metafile  is  being  printed,  and every time you print that
          metafile, the image must be in the same disk (or you will have to
          change your  file).   If GDOS  can't find the image, it will just
          skip over it.  Be warned.
               For all  you programmers,  currently some  programs (such as
          OUTPUT.PRG and  OUTPRINT.PRG) have  difficulty handling metafiles
          with large coordinates.  Try  to  keep  the  coordinate  space as
          small as  possible while still maintaining enough for good output
          quality.


          MISCELLANEOUS COMMENTS

               If you are using the Timeworks Desktop Publisher  ST (TDTP),
          you must  run the  FONTWID.APP program  each time  you modify the
          ASSIGN.SYS file.  Another important  fact  is  that  the relative
          widths  of  the  Timeworks  fonts  are not the same for different
          devices.  What this means is that if  you create  a document with
          TDTP installed for use with an Epson 9-pin printer, then load the
          file into TDTP installed for use with a  laser printer,  the text
          will be  re-flowed.   This may  result in  different page breaks,
          lost text, extra white  space, etc.   The  best solution  to this
          problem is  to create  the document with a TDTP installed for the
          device which will create the final copy.  Another idea  is to use
          Atari's fonts  (if you have them--they are not public domain), as
          the relative sizes between devices is very close (there still may
          be a few differences, but can be fixed readily).
               It should  also be noted that Timeworks' ASSIGN.SYS files is
          a mess.  Apparently they list all the  fonts they  have available
          for all  their device  drivers in one ASSIGN.SYS file.  I suggest
          you create your own based on the information presented here.

               For those of you  who have  seen a  lot of  DEGAS Elite GDOS
          fonts floating around, don't get too excited.  For those to print
          properly (even blocky), you must have matching printer  fonts for
          the  screen  fonts.    GEMFED  or  FONTZ!  greatly  simplify this
          process, but if you intend to create a  complete set  of fonts in
          four or five sizes, you will have a lot of work ahead of you.

               Anyone  creating   fonts  for  the  general  public  (either
          commercial or public domain), try to  remember that  not everyone
          is using  the same kind of monitor or printer you are.  If at all
          possible, create fonts for all the devices I have listed above.

               For those of you creating fonts  with FONTZ!,  you should be
          aware  that  scaling  fonts  may  change  the aspect ratio of the
          characters.  I'll say it again:  Creating high quality fonts is a
          lot of work.  Period.

               One thing  I didn't  mention are  metafile fonts.  These are





          not really  fonts,  but  merely  width  tables  designed  to keep
          correct character spacing in a file when used with different GDOS
          applications.  They are rarely used  and, in  most cases,  can be
          eliminated without any loss of quality.

               Because GDOS  has gone through many revisions, there is some
          confusion over which is the  latest.    When  GDOS  is  loaded, a
          message is  displayed on  the screen  saying it is installed, and
          the  version  number.    The  original   GDOS  displayed  "GEMVDI
          Installed".    After  that,  it  switched  to  "GDOS  Version 1.x
          Installed".  The most common were  1.1, 1.2,  1.3, 1.5,  and 1.8.
          The  newest   revisions  of   GDOS  display   "GDOS  RELEASE  1.x
          Installed", with 1.1 being the newest (1.0 is still widely used).
          As you  can see, it is very important to read the boot-up message
          when determining which  revision  you  are  using.    Also,  as a
          sidenote, if  you can't get RELEASE 1.0 or 1.1, you should try to
          avoid Version 1.8, which had some problems.

               To  prevent  problems  with  some  of   the  device  drivers
          available,  fonts  should  be  listed  in  the ASSIGN.SYS file in
          ascending order by font ID.   Some device  drivers will  not find
          fonts which are listed out of ID order.

               Some  of  the  GDOS  fonts  available  have  the  entire  ST
          character  set  defined,  including  greek,  hebrew,   and  other
          character (most  are unused by the average person).  As you might
          imagine, these take up space, usually, more than 50% of  the font
          file!   So, if  you're running  out of  memory (especially with a
          Mega ST2 and SLM804), you can use FONTZ!  to strip  out the upper
          characters.  Do this by setting the upper ASCII value to 127.

               Many  people  who  have  seen  printouts  of  GDOS text have
          complained that the text is blocky.   This  blockiness is usually
          the result  of font  scaling.  If a device driver does not have a
          font available in  the  requested  size,  it  will  use  the next
          smaller size, or it may double the size of a smaller font.  It it
          uses the next smaller size, the  text will  look strange, because
          it  will  have  the  spacing  of  the  requested  size,  with the
          character size of  the  actually  used  size.    When  doubling a
          smaller font, blockiness will occur, and even then, the requested
          size may not be obtained.  The best  solution to  this problem is
          to be  aware of what size fonts are available, and only use those
          in your files.

               Currently there are rumors of a future version of GDOS which
          supports scalable  outline (or  vector) fonts.  It's important to
          realize that  GDOS does  not create  the characters.   The device
          drivers are  responsible for  creating the actual characters, and
          could be rewritten to support outline fonts without  any (or very
          minor) changes to GDOS.

               Ever since  GDOS was  released for  the ST, people have been
          complaining, saying that GDOS  was supposed  to be  included with
          the ST.   While  Atari may  have planned that originally, I don't





          believe Atari ever stated publicly that GDOS was  to be included.
          Keep in mind that much of the early ST documentation was based on
          the IBM version of GEM, and reflects DRI's handling of  GDOS, not
          Atari's.
               Also, at  this time,  Atari has no plans to incorporate GDOS
          into the TOS ROMs.


          GLOSSARY

               Aspect Ratio - The relation of width to height.  Maintaining
          a constant  aspect ratio  ensures the same proportions regardless
          of size.

               Device (Graphics Device) - Anything used to create some form
          of output, usually on a video screen or printed on paper or film.

               Device Driver  - A computer program used to control a device
          as specified by a "master" application.

               Font - A typeface of a given style and point size.

               GDOS - Graphics Device Operating System; an extension to the
          Atari ST's operating system allowing for the use of various fonts
          and graphics devices.

               GEM - Graphics Environment Manager; the portion of  the ST's
          operating  system  which  is  responsible  for most of the visual
          aspects of the ST.

               Header - A portion of  a  file  (usually  at  the beginning)
          containing various parameters describing the file.

               Line Spacing - The distance between successive line of text,
          usually measured in points.

               Parameter -  A number  or other  symbol used  to represent a
          given attribute (dimension, color, direction, size, mode, etc.)

               Pixel -  Picture element;  a single dot, usually one of many
          used to create a complete image on a  video screen  or printed on
          paper or film.

               Point  -  A  typographical  unit  of  measure; approximately
          1/72".


          COPYRIGHTS, TRADEMARKS, ETC.

               This document is copyright 1988 by  Douglas N.  Wheeler, all
          rights reserved.

               This  document  may  be  reproduced  for  non-commercial use
          without further permission.  For commercial  reproduction, please





          contact the author.

               Any  questions  or  comments  about  this  document  can  be
          directed to:

               Douglas N. Wheeler
               PSC 3 Box 6096
               Travis AFB, CA  94535
               (707) 437-3786
               GEnie address D.N.WHEELER.

               This   document   mentions   several  commercial/copyrighted
          products.   In each  case, it  is to be understood that the names
          are trademarks of their  respective companies  and are  used here
          only as  references.   I am  in no  way connected, either through
          employment or otherwise, to any of these companies.

               I cannot be held responsible for any damages  resulting from
          the use  or misuse of the information contained in this document.
          This  document   was  created   for  the   purpose  of  providing
          information, it is up  to the reader to accept responsibility for
          the results of the use of this information.

               I'd like  to  thank  Paul  Mazurek,  from  Migraph,  for his
          comments and suggestions for this document.

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