gharring@enprt.Wichita.NCR.COM (Gary Harrington) (09/13/89)
I've gotten a couple requests for information on GhostScript. Although
I'm no expert on it, I do have a working copy running on my PC. Following
are some excerpts from the READ.ME and .DOC files that came with my copy:
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Copyright (C) 1987, 1988 by Aladdin Enterprises. All rights reserved. ***
Licensed to the Free Software Foundation, Inc.
Ghostscript is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY. No author or distributor accepts responsibility
to anyone for the consequences of using it or for whether it serves
any particular purpose or works at all, unless he says so in writing.
Refer to the Ghostscript General Public License for full details.
Everyone is granted permission to copy, modify and redistribute
Ghostscript, but only under the conditions described in the
Ghostscript General Public License. A copy of this license is
supposed to have been given to you along with Ghostscript so you can
know your rights and responsibilities. It should be in a file named
COPYING. Among other things, the copyright notice and this notice
must be preserved on all copies.
In other words, go ahead and share Ghostscript, but don't try to stop
anyone else from sharing it farther. Help stamp out software
hoarding!
******** An overview of GhostScript ********
GhostScript is the name of a set of software that provides:
- An interpreter for the GhostScript language, which very
closely resembles the PostScript (TM) language, which in turn bears a
considerable resemblance to Forth; and
- A set of C procedures (the GhostScript library) that
implement the graphics capabilities that appear as primitive
operations in the GhostScript language.
The GhostScript language interpreter is written entirely in C. The
library is written in C, with some assembly-language accelerators for
some platforms. Currently, GhostScript runs on two platform
families:
- IBM PC and compatibles with EGA or compatible graphics
(256K frame buffer required) under MS-DOS 3.1, and
- DEC VAXStation II/GPX under Ultrix with X Windows version 11.
It is very likely that GhostScript will run under other versions of
MS-DOS, and other versions of Unix that support X11, but it has not
been tested in these environments. The VAXStation implementation has
very poor performance, because problems in the X implementation
required very inefficient workarounds: sources at DEC say this is
because the color version of X11 is not well debugged, and the
monochrome version should be more reliable. (GhostScript does not
require color hardware, but will use it if it is present.)
This file applies to version 1.0 of GhostScript, 10 August 1988.
******** Language comparison ********
The GhostScript language bears a very strong resemblance to the PostScript
(TM) language: in fact, unless otherwise noted, it conforms exactly to
PostScript language description (as presented in the April 1986 printing
of the PostScript reference manual published by Addison-Wesley).
******** Graphics comparison ********
The current definition of framedevice only knows about the EGA (in the
MS-DOS implementation) or the X 11 library (in the Ultrix implementation).
******** How to use the current GhostScript interpreter ********
The file name of the GhostScript interpreter is gs.exe (MS-DOS) or gs
(Unix). To run it, you also need the initialization file ghost.ps, and,
in the likely event that you are going to display text, the files
gfonts.ps and romout.ps.
To invoke the interpreter, give the command
gs <filename1> ... <filenameN>
The interpreter will read in the files in sequence and execute them.
After doing this, it listens to the keyboard for further input. Each
line (i.e. characters up to a <return>) is interpreted separately. To
exit from the interpreter, type quit<return>. Control-C is also safe.
The interpreter recognizes the following four command line switches. For
a description of these, see the file GHOSTINT.DOC. They are:
-Dxxx Turn on debugging printout.
-E Disable the normal PostScript handling of errors;
-Mn Force the interpreter's allocator to acquire additional
memory in units of nK.
-Tname:rsize
Trace a procedure within the interpreter.
******** The GhostScript library ********
GhostScript is actually two programs: a language interpreter, and a
graphics library. The library provides, in the form of C procedures, all
the graphics functions of the language, i.e., approximately those
facilities listed in section 6.2 of the PostScript manual starting with
the graphics state operators. In addition, the library provides some
lower-level graphics facilities that offer higher performance in exchange
for less generality.
PostScript is a trademark of Adobe Systems, Incorporated.
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The GhostScript I have outputs only to an EGA screen. Now, presumably, since
GhostScript is Public Domain, anyone is free to take the interpreter and
add other drivers of their own, like PRINTER drivers! This seems to be
what many of us really want, PostScript to dot-matrix or HP LaserJet printer.
For the small job I need it for, I can't justify the $169 purchase of
GoScript, which is the commercial PostScript to printer program.
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Gary Harrington Gary.Harrington@Wichita.NCR.COM
NCR Corporation
Wichita, Kansas