Tuesday, April 8, 2014

Line Bar Printers Gone Wild

The days leading up to a project being due were always hectic times in the computer lab, with midterms and finals being the absolute worst. My shift as a TA helping students in the lab would end by 8 pm, but I'd still be in the lab until 3 or 4 during these periods.

One particular night in late 1980 or early 1981, I was in the lab the night before the big midterm projects where due, when the ribbon of the line bar printer got wrapped around the print bar fingers and basically disassembled it. Perhaps I should explain just exactly what that means, in all its glorious detail.

A line bar printer has a long bar that would move left and right to do the printing. The bar has a large number little metal fingers with the print symbols embossed on the end, sort of like on a typewriter, but the fingers were short - maybe an inch long. These fingers were in groups of four on a unit as I recall, attached all along the print bar by snapping into place. There were multiple identical sets so that the bar could print many characters at the same time with a minimum of movement. So, there were a LOT of these groups of fingers - this will be important to the story shortly. The print bar would just shimmy back and forth only a few inches at a time, but very quickly as the line of print was completed. The speed and momentum of this bar action will also be important to the story very soon.

The lab was packed that night and there were lines at the card punches, the card reader, and the printer. About midnight I was in the glass office in the corner of the lab helping students debug their projects, when the printer made a tremendous screeching noise. To put this in perspective, these line bar printers were loud, thundering away with the heavy impacts of the print process and the bar chug-chugging back and forth sounding like a freight train. So I was accustomed to the noise, but what I heard grabbed my full and undivided attention. I sprang to my feet and ran over to the printer, popped open the hood, and out fell all the little finger groups that the ribbon had pulled off the bar, partially shredding itself in the process. This was not good.

There was no manual for this printer on site, and keep in mind there was no Googling for one either. The lab had dozens of students desperate to get their jobs done and printed, and the lab had but the one printer - this self-dismantled printer. I figured out how to remove the print bar and gathered up all the finger groups, and the last couple were difficult to find, hiding inside the printer where they had fallen. I then set out trying to debug the situation: What order did these finger groups go in? I laid them all out, sorted them by identical groups, and then assembled them back onto the bar in what seemed like a reasonably logical order. The ribbon was pretty shredded in a couple of places where it had torn the fingers from the bar, but was still intact. I just looped the big ribbon spool past the frayed ribbon section so that it would maximize the time before the ribbon would reverse direction and get back to the frayed section. I knew what would happen when that happened, but I didn't know how long that would be from now once the printer got going again.

I purged the print queue, threw together a quick program on the card punches to just print every character across the page, and gave it a try. I don't think any of the letters were in order on that first attempt, but that wasn't the real point. Now I could compare the expected output with the real output and adjust the ordering of the finger groups to match. The second attempt was much closer, although I still had some sequencing problems. I reasoned out my mistakes, reordered a few finger groups, and the printer was now printing correctly as far as I could determine. My hands and face were covered in ink from handling the ribbon and print fingers - it was quite the mess!

I opened up the card reader for jobs, and students were soon back to work. The whole process took about an hour. At least for about an hour, when the frayed section of ribbon came back around and took out the print bar again. At least then I knew what to do, and had it going again in about 15 minutes. The process repeated about every hour until around 4 am when the last student left. You might think it was a long, challenging night, but it wasn't that way to me. I was in the zone, helping students non-stop in between bouts of the printer eating itself and my putting it back together again, with nothing but my wits and determination to see it through.

Man, I miss those days.

1 comment:

  1. ON THE PERSPECTIVE OF A LAB RAT

    Now ... 30 years later ... I have an appreciation for the job of a lab assistant. I remember always feeling frustrated in the computer labs during those days in college. I DREADED going there. Professors were requiring us to do it more often, recognizing that we had to develop those skills and begin using the tools of computerized word processing and printing. But it was new to students and definitely not a smooth process. Actually, it was often agonizing.

    We were all in transition, and I lamented often about why we couldn't just be free to handwrite or type our papers like we always had done. The wait for a lab assistant to explain even how to move through those early steps of typing the first line of text was agonizing and unpredictable (this was in the early days when there were no user interfaces on computer terminals to make it easier to navigate into a word program and begin typing. Forget FORMATTING). Regular people - like me - with no mind for computer programming (and absolutely no interest) - all of a sudden were thrust into a situation where we were donating our time to learning this strange process that was anything but intuitive. We had to memorize certain details and commands in order to turn on a unit and get it ready to begin typing. There were "cheat sheets," but they were still very confusing and time consuming to look through and find what was needed.

    I recall how we "mere mortal" students had to rely heavily upon the computer science students, who seemed to fancy themselves as nearing deity status (which really chapped us English majors. We were appalled to realize that many of these people who were reshaping our world didn't seem to care much about spelling or grammar (not even in their printed and published materials!) - and yet it didn't seem to matter at all for their success! In fact, it seemed as though the more they were looked up to, the more evident their shameful lack of command of the English language actually was! How could this be??. That was especially hard for literary geniuses to swallow at the time. We shared many rants about this fact.

    The period felt chaotic and as though organized planning for school projects was spiraling out of control. Of course, had I met Kent back then, perhaps my opinion would have been different. But likely not. All the computer science-y guys I saw in those labs seemed a little ... odd. A disquieting mix of quirky, some less literate, and arrogant (they KNEW most of us depended on them for our own academic success!). But maybe it was also that we English majors were forced back down to earth - made to descend a little from our own lofty impressions of our self value. After all, now it wasn't enough to read Keats. Inexplicable to us, we were forced to somehow put our thoughts into a ... thing ... and print the resultant work out of a ... thing ... for a grade. Our command of metaphor was used to consider how this computer lab must be where bad people go after they die.

    I love reading about Kent's experiences (and amazing recall for detail) as a TA in the computer lab of the early 80s.

    But while Kent misses those days, I am SOOO glad to be done with them!

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