[TUHS] Determining what was on a tape back in the day

Noel Chiappa jnc at mercury.lcs.mit.edu
Sun Nov 19 04:34:51 AEST 2017

     > From: Will Senn

    > So, I came across this tape:
    > ...
    > I was curious what was on it

'od' is your friend!

If you look here:


there's a thing which is basically 'od' and 'dd' rolled in together, which
allows you to dump any block you want in a variety of formats (ASCII, 16-bit
words in octal [very useful for PDP-11 binary], etc). I wrote it under CygWin,
for Windows, but it only uses the StdIO library, and similar programs (e.g. my
usassembler) written that way work fine under Losenux.

Try downloading it and compiling it - if it doesn't work, please let me know;
it'd be worth fixing it so it does work on Linux.

    > after some fiddling, I figured out that I could get a boot prompt (is
    > that actually from the tape?)

The 0th block does seem to contain some PDP-11 binary - a bootstrap of some
sort. I'll look in more detail in a bit.

    > I was thinking this was a sixth edition install tape of some sort, but
    > if it is, I'm not able to figure it out.

>From what I can see, it's probably a tp-format tape: the 1st block contains
some filenames which I can see in an ASCII dump of it:


    > v7 and look at its content using tm or tp, but then I realized that I
    > didn't have a device set up for TU56

You don't need to mount it on DECTape drive - it's just blocks. Mount it as
an RK05 image, or a magtape, or whatever.

    > When you received an unmarked tape back in the day, how did you go about
    > figuring out what was on it?

Generally there would have been some prior communication, and the person
sending it would have told you what it was (e.g. '800 bpi tar', or whatever).

    > What advice would you give a future archivist to help them quickly
    > classify bit copies of tapes :).

Like I said: "'od' is your friend!"!! :-)


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