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Do You Have a Working Paper Tape Reader?

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Chesler
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Re: scanner?
Chesler   1/6/2014 4:31:08 PM
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Thanks for posting the request, Max.
The paper tape in question is about 56 cm long, and it seems to be 4 bytes per cm, so 224 characters.

Of course I could simply re-write it, and I don't know where I'd get a BASIC interpreter, but if there is too much human in the loop I'm not sure if it's "authentic".  (Ideally I want my printout written with a type ball using a well-used ribbon. :-) )  OCR might feel authentic enough; I suppose I could type in each byte if the tedium doesn't induce errors, and write a quick translator. (Graphics is not my strength, so I can't write the program to read the image.)

Max The Magnificent
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Re: scanner?
Max The Magnificent   1/6/2014 4:52:12 PM
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@Chesler: The paper tape in question is about 56 cm long, and it seems to be 4 bytes per cm, so 224 characters.

Is that all? I was thinking it might be 50 feet long. In that case, if this were mine I'd translate it by hand.

Chesler
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Re: scanner?
Chesler   1/7/2014 11:46:50 AM
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For what it's worth, here is a link to a Flickr image of what the paper tape looks like:



(Unlike floppy disks in old jokes, you can get useful information putting a paper tape into a photocopier :-) )

Max The Magnificent
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Re: scanner?
Max The Magnificent   1/7/2014 11:49:33 AM
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@Chester: For what it's worth, here is what the paper tape looks like:

Hi David -- I think you were trying to include a link to the image of your short paper tape program on Flickr, but for some reason it's not appearing -- if you email me the image I will make it available to folks.

Chesler
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Re: scanner?
Chesler   1/7/2014 12:04:36 PM
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h__p: //www.flicker.com/photos/chesler/11812689353



rfindley
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Re: scanner?
rfindley   1/7/2014 12:40:03 PM
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A single LED (point light source) will cast an image through the holes that expands the farther you go from the tape.  Just move the photodiodes back an inch or so from the tape, to where the projected dot spacing matches the photodiode spacing.

betajet
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CEO
Re: scanner?
betajet   1/7/2014 1:38:36 PM
Oooh!  Even parity!  (More to come)

First line looks like:

10  REM INPUT N ; OUUTPUT N! BY Y-512

A good reference for an ASCII table and paper tape format is the DEC PDP-11 Peripherals Handbook, which is actually available at bitsavers.trailing-edge.com.  It's 28 MB, but all gold :-)

Page B-4 has an ASCII table in octal, which is the easiest way to decode paper tape.

Page B-5 shows how the bits are punched onto paper tape.  Bit 7 (MSb) is even parity on your tape, so ignore it.

Edit: You can also find a good example of paper tape and an ASCII table at Wikipedia.  However, Wikipedia's table is better suited for decoding hexadecimal.

 

David Ashton
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PROGRAM
David Ashton   1/7/2014 10:36:42 PM
I decoded the whole thing (no, not too much time on my hands, just a boring job) and got

10  REM INPUT N ; OUUTPUT N! BY Y-512

20  PRINT "INPUT THE NUMBER THAT YOU WANT THE FACTORIAL OF"

30  INPUT N

40  N=N-1

70  IF N=1 THEN 100

80  F=F*N

90  GOTO 60

100  PRINT F

110  END

I can see how it is supposed to work but a couple of things here
  • in line 80 variable F is not initialised, maybe that machine initialised unknown variables to 1?
  • line 90 jumps back to line 60 which does not exist, probably should be line 40

If the above is true then it should work, multiply N by itself N times.

I don't have a BASIC machine to run it on, does anyone?

David Ashton
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Working!
David Ashton   1/7/2014 11:22:33 PM
How about that!  You can still get good old GWbasic from here

http://gwbasic.webs.com/download.htm

or here, which has manuals as well

http://www.gw-basic.com/downloads.html

Pretty good value for 60K (yes K not M) of program!!

I got the program working -  as I thought, I had to initialise F and get the line numbers right for the jumps, but then it does work:

10  REM INPUT N, OUTPUT N!

20  PRINT "INPUT THE NUMBER THAT YOU WANT THE FACTORIAL OF"

30  INPUT N

35  F=1

70  IF N=1 THEN 100

80  F=F*N

85  N=N-1

90  GOTO 70

100  PRINT F

110  END

It only works up to N=30-something then it overflows.

Thanks guys, have not had this much fun in years!

 

betajet
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CEO
Re: Working!
betajet   1/8/2014 9:39:11 AM
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Now you just need to punch the updated program onto paper tape and you're done!

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