Re: overprinting ASCII on Laserjet?

Robert Wood <rob...@ionet.net> writes:
>
> Neil Franklin wrote:
>
> >
> > Well actually the printer is obeying the CRs. They just have no
> > discernable result on the output.
>
> Ah, but it does, it is interpreting the CR as a line feed

Man to dog: sit. Dog: bark.

A funny definition of obeying :-).


> > > combination are interpreted.  But in another place in the HP codes it says tha
> > t
> > > the LF (linefeed) ASCII 10 is interpreted as CR (carriage return) ASCII 13.
>
> It actually prints as ...
> <any character>
> <second-char>

I would call that broken firmware. Possibly broken as designed, but
definitely broken.

P.S: are you printing directly to the LPTx: from an DOS box or are you
printing from some file view/print program (Notepad?) via an Windows
driver? Is this printer even DOS aware or Windows-only (possible
emulating an LPTx:)?


> > The nearist thing you can do is get an program that understands
> > overstriking and converts it into escape sequences for bold
>
> Huh?  These "poster" files have nothing to do with "bold" printing.  The
> same
> character is not be printed in the same place.  It is usually a 0
> overwritten by a #
> then overwritten by a X.

Ah so. I was thinking of the typical overprinting problems people get
from [tn]roff style bold/underline jobs.


> > BTW: printing the line twice with CR is the wrong way for most of
> > these programs, they usually want <char1> <BS> <char1> <char2> <BS>
> > <char2> ..., they also user <unserscore> <BS> <char> to underline.
>
> Have you ever looked at one of these files?

The type you have described above I have never met.

What type of system produced these? What program?


> Before Dot matrix all there           
> was were                                           
> line printers, so therefore you had to print a whole line at a time.
        
Now it is to me to say "huh".      

The first computer printers were Teletype ASR 2x and 3x(*) and Friden
Flexowriters (I am talking here about the 1950s for mainframes and
1960s for PDPs). These devices all worked one character at a time.

ASCII was originally the control code for such devices. That is
why it contains such things as BS, <HT and the double CRLF.        

And that is why programs like [tn]roff used the char-BS-char trick.

(*) I still remember (far to well) using an 1953 ASR 33. Awfull.


Line-at-a-time printers were a later development to keep up with
processor speed increases (this was batch processing days, where the
CPU output everything to cardpunch or printer, no disks).

Such devices had one line of RAM which was first filled with the
characters before letting them out. They may have emulated CR LF but
an single line end would be more natural to these.                              


> you print a              
> line of 0's, then you overprint with a line of #'s, then you print a
> third time on the
> same line with X's.

Actuall the only line-at-a-time printer I have ever seen (on an Pr1me
750) about 15 years ago) would make this impossible. It used one pin
per char and "wriggled" the print assembly a few pixels back and fro, 
while steadily advancing the paper. Overstrike would have required  
reversing the paper movement (never an good thing to do).       


> I understand that Laser printers are page printers and that each
> character is sent                                                
> to the printer as a bunch of dots to fill up a space.        

Bunch of dots only on cheaper ones. More expensive ones recieve ASCII     
with embedded codes (PCL) or ASCII coded drawing programs (PS).


> 0 then put a # in the same space you should fill in more or the dots in
> our
> "rectangle", that when you add the X to the mix you fill in even more
> dots in our                           
> rectangle.

That is what should happen. If the printer firmware is not broken.   


> "Transparency" setting
> on the HP may solve this, but I have not been able to find a good
> example of how to
> use it in this situation,

Transparency? What good would that do?

I would try having an look at the PCL positioning escape sequences.
Quasi force the rasteriser to work there where you want it to.

I have not got any PCL manual, so I can not point out the actual
sequence to use.


> I have seen too many print errors where text overwrote other text on my
> laser to
> just give this up as hopeless.

Most likely wrongly calculated positioning sequences. I have done that
myself when writing PostScript drivers. PS also has positioning
commands, misscalculating their parameters gives such mess.


> already worked out how to print the old line printer posters on a laser
> printer.  I
> can not believe I am the first to try this.  The Dot Matrix printer will
> eventually become an oddity that is only used in special circumstances,

And an oddity which exactly the old diehards will be the last to leave.

Actually I have gone paperless. I have yet to find any ASCII that will
not render on-screen.


--
Neil Franklin, Nerd, Geek, Unix Guru, Hacker, Mystic
nei...@franklin.ch.remove http://neil.franklin.ch/
20th century record companies fit the 21st century data highways
as good as 19th century stagecoaches fit the 20th century freeways

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