Copyright (C) 1989, 1990, 1991, 1993 Aladdin Enterprises.  All rights reserved.

This file is part of Ghostscript.

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.

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

This file, make.doc, describes how to install Ghostscript, and how to
build Ghostscript executables from source.

For an overview of Ghostscript and a list of the documentation files, see
README.

********
******** Installing Ghostscript
********

To install the interpreter, you need:
	- The interpreter executable:
		- On MS-DOS and VMS systems, gs.exe.
		- On MS-DOS systems, if you are using the Watcom compiler,
		  the DOS extender, dos4gw.exe.
		- On Unix systems, gs.
	- The interpreter initialization files:	gs_*.ps.
	- The font map: Fontmap.
	- The default font: uglyr.gsf.

See use.doc for a description of the search algorithm used to find these
files.

You do not need any of these files when using the library; however, the
library currently provides no way to install fonts.  This is obviously
ridiculous and will be fixed sometime in the future.

********
******** Building Ghostscript from source
********

Ghostscript is generally distributed in the form of a compressed tar file.
When unpacked, this file puts all the Ghostscript files in a directory
called gs.  Ghostscript is also available in the form of PC-compatible ZIP
files.

Ghostscript is described by a collection of several makefiles:

	gs.mak - a generic makefile used on all platforms (except VMS).
	devs.mak - a makefile listing all the device drivers.
	*.mak - the makefiles for specific platforms.

You may need to edit the platform-specific makefile if you wish to change
any of the following options:

	- The default search path(s) for the initialization and font files
(macro GS_LIB_DEFAULT);

	- The debugging options (macro TDEBUG);

	- The set of device drivers to be included (DEVICE_DEVS
	and DEVICE_DEVS1..9 macros);

	- The set of optional features to be included (FEATURE_DEVS macro).

The platform-specific makefile will include comments describing all of
these items except the DEVICE_DEVS options.  The DEVICE_DEVS options are
described in devs.mak, even though the file that must be edited is the
platform-specific makefile.

The makefiles distributed with Ghostscript define these options as
follows:

	- GS_LIB_DEFAULT: on Unix systems, /usr/local/lib/ghostscript
and /usr/local/lib/ghostscript/fonts; on MS-DOS systems, C:\GS.

	- TDEBUG: no debugging code included in the build.

	- DEVICE_DEVS*: platform-specific, see below.

	- FEATURE_DEVS: platform-specific.

There are also platform-specific options described below under the
individual platforms.  See the "Options" section near the beginning of the
relevant makefile for more information.

If you are including a dot-matrix printer driver, you may wish to
customize the default resolution parameters in devs.mak.

To build the interpreter, you need all the .h and .c files (and .asm files
for MS-DOS) included in the distribution, as well as the makefiles.

The command
	make clean
removes all the files created by the build process (relocatables,
executables, and miscellaneous scratch files).  If you want to save the
executable, you should move it to another directory first.

********
******** How to build Ghostscript from source (MS-DOS version) ********
********

To find out what devices the makefiles distributed with Ghostscript
select for inclusion in the executable, find the lines in the
appropriate makefiles of the form
	FEATURE_DEVS=<list of features>
and
	DEVICE_DEVS=<list of devices>
	(similarly DEVICE_DEVS1... up to DEVICE_DEVS9)
The relevant makefiles are:
	Turbo C: tc.mak
	Turbo C++/Borland C++, MS-DOS: bc.mak
	Borland C++, MS Windows: bcwin.mak
	Microsoft C/C++ 7.0, MS-DOS: msc.mak
	Watcom C/386, MS-DOS: watc.mak
The options were chosen to strike a balance between RAM consumption
and likely usefulness.  (Turbo C is limited to 640K and does not
support code overlaying; Borland C++ is limited to 640K, but supports
code overlaying under MS-DOS; Watcom C/386 is not limited to 640K.)

To build Ghostscript, you need MS-DOS version 3.3 or later, and a
(Borland) Turbo C/C++, Borland C/C++, Microsoft C/C++ (version 7), or
Watcom C/386 development system.  Details are given below.

As noted above, the default configuration generates an executable that
assumes the directory where 'make' was run should be the final default
directory for looking up the Ghostscript initialization and font files.

To build the Ghostscript executable, all you need to do is give the
command
	make
You must have COMMAND.COM in your path to build Ghostscript.

There is a special 'make' target that simply attempts to compile all the
.c files in the current directory.  Some of these compilations will fail,
but the ones that succeed will go considerably faster, because they don't
individually pay the overhead of loading the compiler into memory.  So a
good strategy for building the executable for the first time, or after a
change to a very widely used .h file, is:
	make begin
and then
	make
to do the compilations that failed the first time.

Note: if you get the Ghostscript sources from a Unix 'tar' file and unpack
the file on a MS-DOS machine, the files will all have linefeed instead of
carriage return + linefeed as the line terminator, which may make the C
compiler unhappy.  I don't know the simplest way to fix this: just reading
each file into an editor and writing it back out again may be sufficient.
You will probably have to do this to the .c, .h, and .bat files.

Borland environment
-------------------

To compile Ghostscript with the Borland environment, you need either Turbo
C (version 2.0 or later) or Turbo C++ or Borland C++ (version 1.0 or
later); specifically, the compiler, 'make' utility, and linker.  You also
need either the Borland assembler (version 1.0 or later) or the Microsoft
assembler (version 4.0 or later).  Before compiling or linking, you should
execute
	echo !include "tc.mak" >makefile
(for Turbo C and MS-DOS), or
	echo !include "bc.mak" >makefile
(for Turbo C++ or Borland C++ and MS-DOS), or
	echo !include "bcwin.mak" >makefile
(for Turbo C++ or Borland C++ and Microsoft Windows), or

Besides the source files and the makefiles, you need:
	turboc.cfg (the flags and switches for Turbo C)
	gs.tr (the linker commands for the interpreter)
	*.bat (a variety of batch files used in the build process)

There are extensive comments in the aforementioned .mak files
regarding various configuration parameters.  If your configuration is
different from the following, you should definitely read those
comments and see if you want or need to change any of the parameters:
	- The compiler files are in c:\tc (for Turbo C) or c:\bc (for
Turbo C++ or Borland C++) and its subdirectories.
	- You are using the Borland assembler (tasm).
	- You want an executable that will run on any PC-compatible,
regardless of processor type (8088, 8086, V20, 80186, 80286, V30, 80386,
80486) and regardless of whether a math coprocessor (80x87) is present.

NOTE: Borland C++ 3.0 has two problems that affect Ghostscript (these
problems are fixed in Borland C++ 3.1):

	- The assembler, tasm, often crashes when attempting to
assemble gdevegaa.asm.  If this happens, try again, or use another
assembler (e.g., an older version of tasm) if you have one, or set
USE_ASM=0 in the makefile.

	- The math library for Microsoft Windows, mathwl.lib, has a
bug that causes floating point numbers to print incorrectly.  Contact
Borland for a corrected version.

If you are compiling Ghostscript with Turbo C++ 1.0, remove the
`.swap' directive from bc.mak, and use the -s switch on the `make'
command line.  (All later versions of the Borland environment
recognize this directive.)

Note that although the Microsoft Windows version of Ghostscript will
run under Windows 3.0, it uses routines from the Windows 3.1 SDK, so
you need the Windows 3.1 SDK and header files to compile it.  In
practice, this means that you need Borland C++ 3.1; Borland C++ 3.0
doesn't include the necessary headers.

Microsoft environment
---------------------

To compile Ghostscript with the Microsoft environment, you need
Microsoft C/C++ 7.0 or later with its associated `nmake' utility and
linker.  Before compiling or linking, you should execute
	echo !include msc.mak >makefile

Besides the source files and the makefiles, you need:
	gs.tr (the linker commands for the interpreter)
	*.bat (a variety of batch files used in the build process)

We have found the Microsoft `nmake' program to be very unreliable; it
may crash partway through the build process with a variety of error
messages, or no error message.  

We have not been able to test the Microsoft compiler in a wide
variety of configurations, because it is so much slower than the
Borland compiler (about 5 times) and because there is apparently no
way to get it to write its error messages to a file.  If you
encounter problems with the Microsoft environment, please contact
Aladdin Enterprises.

Watcom environment
------------------

To avoid annoying messages from the DOS extender, add the line
	set DOS4G=quiet
to your autoexec.bat file. 

To compile Ghostscript with the Watcom C/386 compiler, you need to create
a makefile by executing

	echo !include watc.mak >makefile

To build Ghostscript, execute

	wmake -u

********
******** How to build Ghostscript from source (Unix version) ********
********

The makefile distributed with Ghostscript selects the following devices
for inclusion in the build:
	Display: X Windows driver.
	File output: pbm, pbmraw, pgm, pgmraw, ppm, and ppmraw drivers.

Before compiling or linking, you should execute

	ln -s unix-cc.mak makefile
or	ln -s unix-gcc.mak makefile
or	ln -s unix-ansi.mak makefile

(if your Unix system doesn't support symbolic links, omit the -s switch)
depending on whether your C compiler is a standard Kernighan & Ritchie C
compiler, gcc being used in ANSI mode, or an ANSI C compiler other than
gcc respectively.  (If you want to use gcc in non-ANSI mode, use
unix-cc.mak and define the CC macro to refer to gcc.)

The unix-*.mak files are actually generated mechanically from *head.mak,
*tail.mak, gs.mak, and devs.mak.  If for some reason your copy of
Ghostscript doesn't include the unix-*.mak files, invoke the
	tar_cat
shell script to construct them.

If the X11 client header files are located in some directory which your
compiler does not automatically search, you must change the XINCLUDE macro
the makefile to include a specific -I switch.  See the comment preceding
XINCLUDE in the makefile.

The only important customization of the X11 driver is the choice of
whether or not to use a backing pixmap.  If you use a backing pixmap,
Ghostscript windows will redisplay properly when they are covered and
exposed, but drawing operations will go slower.  This choice is controlled
by a line in the file gdevxini.c that says
	private int use_backing = 1;
Changing this line to read
	private int use_backing = 0;
will disable the use of a backing pixmap.  However, portions of the
Ghostscript window may not be properly redrawn after the window is
restored from an icon or exposed after being occluded by another window.

Some versions of the X server do not implement tiling properly.  This will
show up as broad bands of color where dither patterns should appear.  If
this happens, in the file gdevx.c, change
	private int use_XSetTile = 1;
to
	private int use_XSetTile = 0;
and recompile.  The result will run a lot slower, but the output should be
correct.  If this fixes the problem, report it to whoever made your X
server.

Similarly, some versions of the X server do not implement bitmap/pixmap
displaying properly.  This may show up as white or black rectangles where
characters should appear, or characters may appear in "inverse video"
(e.g., white on a black rectangle).  If this happens, it may help you to
change, in the file gdevx.c,
	private int use_XPutImage = 1;
to
	private int use_XPutImage = 0;
and recompile.  Again, there will be a serious performance penalty; again,
if this fixes the problem, notify the supplier of your X server.

Currently Ghostscript is set up to compile and link in a generic Unix
environment.  Some Unix environments may require changing the LDFLAGS
macro in the makefile.

All you need to do to make an executable is invoke the shell command
	make

Ghostscript uses ANSI syntax for function definitions. Because of this,
when compiling with cc, it must preprocess each .c file to convert it to
the older syntax defined in Kernighan and Ritchie, which is what most
current Unix compilers (other than gcc) support.  This step is
automatically performed by a utility called ansi2knr, which is included in
the Ghostscript distribution.  The makefile automatically builds ansi2knr.

The ansi2knr preprocessing step is included in the makefile rule for
compiling .c files.  ansi2knr creates a file called _temp_.c to hold the
converted code.  If you want to change this name for some reason, it is
defined in unix-cc.mak.

Platform-specific notes
-----------------------

386 Unix:
	gcc versions older than 1.38 on Intel 80386 systems do not
compile Ghostscript correctly using the -O option.  Do not use -O in
these environments.
	gcc 1.39 under 386BSD has a bug that causes float-to-integer
conversions to compile incorrectly.  Do not use this version of gcc.
	X11R5 may need #include <stddef.h> in x_.h.
	Also see below regarding System V platforms.

Apollo:
	You must run the compiler in ANSI-compatible mode (i.e., set AK=
<null string> in the makefile); otherwise, it gives incorrect error
messages for any function declared as returning a float value.
	The Apollo compiler may not compile Ghostscript correctly.  If you
get unexpected crashes at run time, use gcc.

Convex:
	Use unix-ansi.mak.  Do not invoke optimization (-O1): there
are compiler bugs that lead to incorrect code.  Set CFLAGS to
	-fn -tm -no c1

DEC (Ultrix):
	Many versions of DEC's X server (DECwindows) have bugs that
require setting use_XPutImage or use_XSetTile to 0, as described above.

GNU make (any platform):
	GNU make 3.59 can't handle the final linking step in some cases;
use the platform's standard make (e.g., /bin/make) if this happens.

H-P 700 series:
	Use the compiler flags -Aa +O3 (*not* -O).

ISC Unix:
	For ISC Unix with gcc, an appropriate make invocation is:
	make XCFLAGS="-D__SVR3 -posix" LDFLAGS="-shlib -posix" \
	     EXTRALIBS="-linet -lnsl_s"
If this doesn't work for you, try removing the -shlib.  ISC Unix may
also need one or more of the following in EXTRALIBS: -lpt, -lc_s.
See also under "386 Unix" above.

MIPS:
	There is apparently a bug in the MIPS C compiler which causes
gxdither.c to compile incorrectly if optimization is enabled (-O).  Until
a work-around is found, do not use -O with the MIPS C compiler.

NeXT:
	Use unix-gcc.mak, but change the name of the compiler (CC=)
from gcc to cc.  Also, include -D_NEXT_SOURCE in CFLAGS, and change
the two occurrences of sys/time.h to ansi/time.h.  You may also find
it useful to add the following line to Fontmap:
		/Ohlfs	/Courier	;

RS/6000:
	Due to compiler bugs, most of the obvious ways to compile
Ghostscript on the RS/6000 don't work.  You should use the following
command line, or a similar one with a different compiler (see below):

	make -f unix-ansi.mak CC=c89 \
	XINCLUDE=-I/usr/misc/X11/include XLIBDIRS=-L/usr/misc/X11/lib

You must also edit the makefile (unix-ansi.mak or unix-cc.mak) to define
CFLAGS as -DSYSV -D_POSIX_SOURCE, and to change INSTALL to
/usr/ucb/install.  (If -DSYSV produces a complaint about the functions
index and rindex not being defined, try removing it.)

Even beyond all this, many people have trouble with Ghostscript on
the RS/6000.  The usual symptom is that it compiles and links OK, but
produces garbaged output on the screen.  The problem may be related
to particular versions of AIX or the X server; we don't have enough
information at this time.  The following combinations of AIX and X
are known to fail:
	AIX 3.1.5, MIT X11R4, c89, unix-ansi.mak
	AIX 3.2.0 or 3.2.1, c89 or xlc
The following combinations are known to work:
	AIX 3.1.5, MIT X11R5, c89, unix-ansi.mak
	AIX 3.2, MIT X11R5, xlc 1.2.0.9, unix-ansi.mak
	AIX 3.2, c89, unix-ansi.mak -- but you must compile
	  without optimization (no -O)
	AIX 3.2.0 or 3.2.1, cc, unix-cc.mak, no -O
It may be that just including -Dconst= in the command line is
sufficient to get around the bugs in the AIX 3.1.5 compiler.

Apparently some (but not all) releases of the C library declare the hypot
function: if the declaration in math_.h produces an error message, try
removing it.  Also, the IBM X11R3 server is known to be buggy: use the MIT
X server if possible.

SCO Unix/Xenix:
	The SCO Unix C compiler apparently can't handle the Pn macros
in std.h.  If you get strange compilation errors on SCO Unix, see if
you can get a compiler fix from SCO.  Meanwhile, to use gcc with SCO
ODT, see gcc-head.mak for the appropriate switch settings.  See also
under "386 Unix" above.
	gcc 2.3.3 produces code that causes a core dump on machines
that don't have hardware floating point, because of a bug in SCO's
floating point emulator.  Use a different compiler on these machines.
	If you aren't using the X11 driver, you need to add -lsocket
to the linker command (near the end of the unix-*.mak file) in order
to get the date/time functions linked in.
	If you want to use direct frame buffer addressing instead of
X Windows, include the relevant frame buffer device(s) (ega.dev,
vga.dev, etc.) and change gdevevga.c to gdevsco.c as indicated in
devs.mak.  Note: this does not work with SuperVGA displays, except
for 800x600x16 mode.
	If your compiler accepts the -Xt and -Xa switches, use -Xt.
Even though this causes the compiler to use incorrect rules for
computing the result types of << and >>, -Xa enables "optimizations"
that produce incorrect code.
	For SCO ODT 2.0, in addition to -D__SVR3 and -DSYSV, you need to
specify -Dsco, -DUSG, and -DMALLOC_0_RETURNS_NULL.  For SCO ODT, you need
EXTRALIBS=-lX11 -lsocket -lmalloc, or maybe only -lsocket (depending on
the version), and for SCO ODT 2.0, you also need to specify -lc_s.  For
SCO Xenix, you need EXTRALIBS=-lmalloc.
	For all SCO systems, set XINCLUDE= and XLIBDIRS=.

Sun:
	The Sun unbundled C compiler (SC1.0) doesn't compile Ghostscript
properly if the -fast option is selected: Ghostscript core-dumps in
build_gs_font.  Use -g, or use gcc.
	The Sun version of dbx often gives up with an error message when
trying to load Ghostscript.  If this happens, use gdb instead.  (gdb is
more reliable than dbx in other ways as well.)
	Solaris 2.2 may require setting EXTRALIBS=-lsocket.
	In SunOS 4.1.[23], you may get these undefined symbols when linking:
		_get_wmShellWidgetClass
		_get_applicationShellWidgetClass
Compiling "-Bstatic -lXmu -Bdynamic" appears to work.  To solve the
problem if you are using OpenWindows 3.0 (X11R4-based Xt), please contact
your local Sun office and request the following patches:
	Patch i.d.      Description
	100512-02       4.1.x OpenWindows 3.0 libXt Jumbo patch
	100573-03       4.1.x OpenWindows 3.0 undefined symbols when using
				shared libXmu
A source patch for use with the MIT X11R4 libraries was developed by Conrad 
Kimball (cek@sdc.boeing.com); it retrofits into R4 some fixes made in R5 to
get around this problem. The patch is on export in [1/93]
        contrib/X11R4_sunos4.1.2_patch_version3.Z

System V Unix platforms:
	If you are using a stock System V platform that lacks rename
and gettimeofday, change PLATFORM=unix_ in the makefile to
PLATFORM=sysv_.
	You will probably need to change the definition of INSTALL (near
the beginning of the makefile) from install to /usr/ucb/install.

********
******** How to build Ghostscript from source (VAX/VMS version) ********
********

The files VMS-CC.MAK and VMS-GCC.MAK are VMS DCL command files which
build Ghostscript from scratch using either the DEC C compiler, CC, or
the Free Software Foundation's GNU C compiler, GCC.  Accordingly, you
must have one of these two compilers installed in order to build
Ghostscript.  (Other C compilers may work: CC and GCC are the only two
compilers tested to date.)  These two command files build and store
the Ghostscript library in the object library GS.OLB.  If you have
DECwindows (X11) installed on your system, the executable images GS.EXE,
GT.EXE, and XLIB.EXE will also be built.

Some environments use the DWTLIBSHR library for providing the X
Windows intrinsics, and some use the XTSHR library.  XTSHR is newer,
and is part of the DECwindows/Motif product.  However, DEC is still
distributing versions of VMS with DWTLIBSHR.  If your environment
uses XTSHR, replace DWTLIBSHR in the list of link libraries with
XTSHR.

The only important customization of the X11 driver is the choice of
whether or not to use a backing pixmap.  If you use a backing pixmap,
Ghostscript windows will redisplay properly when they are covered and
exposed, but drawing operations will go slower.  This choice is controlled
by the line in the file gdevx.c that reads
	private int use_backing = 1;
Changing this line to read
	private int use_backing = 0;
will disable the use of a backing pixmap.  However, portions of the
Ghostscript window may not be properly redrawn after the window is
restored from an icon or exposed after being occluded by another window.

Many versions of DEC's X server (DECwindows) have bugs that require
setting use_XPutImage or use_XSetTile to 0, as described above.  These
show up as broad bands of color where dither patterns should appear, or
characters displayed white on top of black rectangles or not displayed at
all.  If this happens, change use_XSetTile or use_XPutImage to 0 as
described above.  The result will run a lot slower, but the output will be
correct.  Report the problem to DEC, or whoever supplied your X server.

Ghostscript uses ANSI syntax for function definitions. Thus, when using
the DEC C compiler, each .C file is converted to the older C syntax defined
in the first edition of Kernighan and Ritchie and stored in a .CC file.
This step is performed by VMS-CC.MAK using the ansi2knr utility included
in the Ghostscript distribution.  If you are building a debuggable
configuration, the .CC files will be left behind by VMS-CC.MAK for use by
the VMS Debugger; otherwise, they will be deleted.

If you have DEC's C compiler, issue the DCL command
        $ @VMS-CC.MAK
to build Ghostscript.  If you have GNU C, issue the DCL command
        $ @VMS-GCC.MAK
to build Ghostscript.

The option "DEBUG" may be specified with either command file in order to
build a debuggable Ghostscript configuration:
        $ @VMS-CC.MAK DEBUG    -or-   $ @VMS-GCC.MAK DEBUG

In order to specify switches and file names when invoking the interpreter,
define GS as a foreign command:
        $ GS == "$disk:[directory]GS.EXE"
where "disk" and "directory" specify the disk and directory where Ghostscript
is located.  For instance,
        $ GS == "$DUA1:[GHOSTSCRIPT]GS.EXE"
To allow the interpreter to be run from any directory, define the logical
GS_LIB which points to the Ghostscript directory
        $ DEFINE GS_LIB disk:[directory]
This allows Ghostscript to locate its initialization files stored in the
Ghostscript directory -- see use.doc for further details.  Finally, to
invoke the interpreter, merely type GS.  Although DCL normally converts
unquoted parameters to upper case, C programs receive their parameters in
lower case.  That is, the command
        $ GS -Isys$login:
passes the switch "-isys$login" to the interpreter.  To preserve the
case of switches, enclose them in double quotes; e.g.,
        $ GS "-Isys$login:"

If you add compiled fonts to your system as described in the fonts.doc
file, you must C-compile them in an environment that includes some
definitions from vms-cc.mak.  Find the section of vms-cc.mak with the
comment "Give ourself a healthy search list for C include files" and
execute the immediately following DEFINE commands before C-compiling the
fonts.

********
******** A guide to the files ********
********

General
-------

There are very few machine dependencies in Ghostscript.  A few of the .c
files are machine-specific.  These have names of the form
	gp_<platform>.c
specifically
	gp_dosfb.c (all MS-DOS platforms)
	gp_msdos.c (all MS-DOS platforms)
	gp_itbc.c (MS-DOS, Borland compilers)
	gp_iwatc.c (MS-DOS, Watcom or Microsoft compiler)
	gp_unix.c (all Unix)
	gp_sysv.c (System V Unix)
	gp_vms.c (VMS)
There are also some machine-specific conditionals in files with names
<something>_.h.  If you are going to extend Ghostscript to new
machines or operating systems, you should check the *_.h files for
ifdef's on things other than DEBUG, and you should probably count on
making a new makefile and a new gp_ file.

Library
-------

Files beginning with gs, gx, or gz (both .c and .h), other than gs.c
and gsmain.c, are the Ghostscript library.  Files beginning with gdev
are device drivers or related code, also part of the library.  Other
files beginning with g are library files that don't fall neatly into
either the kernel or the driver category.

Interpreter
-----------

gs.c is the main program for the language interpreter.

Files beginning with z are Ghostscript operator files.  The names of the
files generally follow the section headings of the operator summary in
section 6.2 of the PostScript manual.

.c files beginning with i, and .h files not beginning with g, are the
rest of the interpreter.  See the makefile for a little more information
on how the files are divided functionally.

There are a few files that are logically part of the interpreter, but that
are potentially useful outside Ghostscript, whose names don't begin with
either g, z, or i:

	s*.c (a flexible stream package, including the Level 2 PostScript
'filters' supported by Ghostscript);