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POSTSCRIPT
2-16 XEROX DOCUPRINT NPS GUIDE TO USING PAGE DESCRIPTION LANGUAGES
• Illegal characters adjacent to legal characters. If there is no
white space character (as defined in the PostScript Language
Reference Manual, second edition) between the illegal
character or characters and legal PostScript characters, then
that combination can be redefined to be the legal PostScript
substring only, as shown in these examples:
(showpage\004) cvn {showpage} def
(sp\004) cvn {sp} def
Note: It is not desirable to redefine a legal substring ABC as
some other legal substring XYZ in the illegal token initialization
file. For instance, although showpage frequently is redefined by
PostScript code to be sp for brevity, it may seem to make sense
to redefine sp <control D> as showpage. However, if the client
application creating the PostScript defines sp to mean show
rather than showpage, then to have sp <control D> initialized to
mean showpage is an error.
Also, due to case sensitivity, some patterns may have to appear
with the same case variety as in the PostScript jobs to be
processed.
Because there may be an infinite number of character
combinations, the system administrator is encouraged to
redefine only known or suspect problem tokens.
Multiple jobs in one input file
Note that the above control-D handling does not perform true
PostScript job encapsulation. Therefore, the following PostScript job
situations may cause problems. All of these problems are due to
having multiple PostScript jobs in one input file. If problems occur,
break the concatenated masters into separate input files.
• Because control-Ds are not interpreted as end-of-job (EOJ),
PostScript virtual memory (VM) is not restored before the next
job. This means that the next job environment is not “clean,”
which may or may not cause problems. PostScript VM may also
run out since VM is not restored by control-D. Note that all
Xerox PostScript products do restore VM at the end of their
input file, so single PostScript jobs per input file are always
handled correctly.
• Some of the PostScript jobs execute exitserver, which stays in
effect until EOJ. Because the control-Ds are not interpreted as
EOJ, subsequent non-exitserver job definitions become
permanent, which could consume all of the PostScript VM or
cause other PostScript problems.
• A job executes code that flushes the input data up to EOJ.
Because the control-D is not interpreted as EOJ, it does not
stop the flushing. Therefore, the rest of the PostScript jobs in
the input file are ignored.