TUHS January 2022

tuhs@tuhs.org

79 participants
47 discussions

by Douglas McIlroy

> It would be nice to hear about the rationale from a primary source. Assembly language was deemed a last resort, especially as portability was coming to the fore. As I wrote in A Research Unix Reader, "Assembly language and magic constants gradually declined from the status of the 'real truth' (v4) to utterly forgotten (v8)." In v7, assembler usage was demoted to the bottom of syscall man pages. It could also be found in /usr/src/libc/sys/*.s Doug

2 years, 11 months

vi on v7

by Will Senn

Well, hallelujah, after much travail (I've tried this every Christmas for at least 5 years now), I have succeeded in building vi on v7 from 2bsd. Had to patch the c compiler to enlarge the symbol table, tweak some stuff here and there, but it finally built and installed without any errors, yay. Now, I just want it to do some editing, preferably in visual mode. I can call it as ex or vi: # ex : or # vi : and q will exit, yay, again! I have at least two problems: 1. It's not going "full" screen, even with TERM=vt100 or TERM=ansi set (not that I was surprised, but it'd be nice)... 2. If I type a for append and type something, there's no way to get back to the : prompt (ESC doesn't seem to work). 3. I'd like manpages (figure they might help with the above), but they're on the tape as .u files? I'm hoping this triggers some, oh yeah I remember that, type responses. Thanks, Will

2 years, 11 months

asm helper routines in v7

by Will Senn

So, in v6, it was possible to use the mesg function from the system library with: ed hello.s / hello world using external mesg routine .globl mesg mov sp,r5 jsr r5,mesg; <Hello, World!\n\0>; .even sys exit as hello.sld -s a.out -l a.out Hello, World! This was because v6 included mesg in the library, in v7, it doesn't look like mesg is included, so doing the same thing as above requires that code to write the message out be included and in addition system call names are not predefined, so exit and write have to be looked up in /usr/include/sys.s, resulting in the v7 equivalent file: ed hello2.s / hello world using internal mesg routine mov sp,r5 jsr r5,mesg; <Hello, World!\n\0>; .even sys 1 mesg: mov r0,-(sp) mov r5,r0 mov r5,0f 1: tstb (r5)+ bne 1b sub r5,r0 com r0 mov r0,0f+2 mov $1,r0 sys 0; 9f .data 9: sys 4; 0:..; .. .text inc r5 bic $1,r5 mov (sp)+,r0 rts r5 as hello2.s a.out Hello, World! My questions are: 1. Is mesg or an equivalent available in v7? 2. If not, what was the v7 way of putting strings out? 3. Why aren't the system call names defined? 4. What was the v7 way of naming system calls? Will

2 years, 11 months

New Version of Installing and Using Research Unix Version 7 in the SimH PDP-11/45 and 11/70 Emulators Available

by Will Senn

All, I've completed a new version of my "Installing and Using Research Unix Version 7 in the SimH PDP-11/45 and 11/70 Emulators" tutorial/document (wow, that's a mouthful). I'm calling it Version 2.0 - It is a completely reorganized, updated, and edited version of the document. The blog post announcement is on the blog: https://decuser.blogspot.com/ and the pdf is on google drive: https://drive.google.com/file/d/1gDBxULlpLwezH-1RO_3ou_W7trElgSgT/view?usp=… The new doc covers building a working v7 instance from tape files that will run on the SimH emulator. First, the reader is led through the restoration of a pristine v7 instance from tape to disk. Next, the reader is led through adding a regular user, making the system multi-user. Then, the reader is shown how to make the system multi-session cable allowing multiple simultaneous sessions. Finally, the system is put to use with hello world, DMR style, and the learn system is enabled. It also includes a hyperlinked table of contents. My hope is that the new version will be more useful than the prior version, as well as more accurate. I really appreciate the input and feedback y'all have given me over the intervening years. Regards, Will

2 years, 11 months

Re: [TUHS] roff(7) [ and other related stuff ]

by jnc＠mercury.lcs.mit.edu

> From: John Cowan > Why use C syntax? What was wrong with Fortran, Lisp, or Cobol syntax, > extended to do what you wanted? Why do all hammers look basically the same? Because there's an 'ideal hammer', and over time hammer design has asymtoted toward that 'ideal hammer' design. One can't just keep improving the design indefinitely - diminishing returns set in. So I suspect there is, to some degree, a Platonic 'ideal syntax' for a 'classic block-structured' programming language, and to me, C came pretty close to it. I except LISP from that assessment, because LISP is built around a fundamentally different model of how computations/algorithms are organized, and C and LISP aren't directly comparable. But that realization points to a deeper bug with the 'Platonic ideal language' concept above, which is that languages are fundamentally, albeit at a very deep conceptual level, tied to the basic concept of the computing hardware they are to run on. C/COBOL/FORTRAN/etc are all for von Neumann-like (in a broad sense) computing engines - a single thread of computation, which happens sequentially. But we've pushed that paradigm about as far as it can go, we're into diminishing returns territory on that one. The future, starting with the hardware, will be very different - and will need quite different languages. (Go, from what little I know of it, is a baby step in this direction - it is intended to make it easy to use multiple simultaneous loci of execution, making use of the mutiple cores that are common now.) I suspect we'll be shifting to radically different paradigms, 50 years from now - massively parallel computing meshes (think Connection Machines on steroids - or the human brain), and those will use fundamentally different computing paradigms, and programming languages for them, which in turn will need very different syntax. Noel

2 years, 11 months

Re: [TUHS] roff(7) [ and other related stuff ]

by Douglas McIlroy

> Lisp, _that's_ elegant. The machine shines through Lisp even more brightly than it does through C. Lisp attains incredible power from a tiny base: car, cdr, cons, cond, T, F, null, lambda, def, exuding elegance that survives even in a raging sea of parentheses. For Lisp-friendly applications nowadays, I prefer Haskell, which is much further away from the machine. Haskell code approaches--and sometimes surpasses--the cleanliness of good mathematical notation. For string processing, I remember Snobol 3 with great fondness. But for everyday work with arrays and numbers, C is the workhorse. Still, I wish that C would evaluate comma expressions in parallel rather than in series, as in (a,b) = (b,a). Doug

2 years, 11 months

v7 /etc/ttys and /usr/adm/wtmp shenanigans

by Will Senn

I enabled user accounting on my v7 instance and I noticed it "growing without bound" and while this is noted as a possibility in the ac(1) man page, I was pretty sure the original authors didn't mean 30k a second. I scratched my head and thought for a while and then started experimenting to see what the heck was going on. I removed /usr/adm/wtmp (which I had created to enable accounting in the first place) and the little red disk write arrow on my mac went away, but not the little green disk read arrow... hmm. Something was keeping my v7 instance very busy reading disk, that was for sure. I went through a few (dozens) more tests and experiments, reread a bunch of man pages, Ritchie's v7 install note, and thought some more and here's what I came up with... If you modify your system to add dci lines and you enable some ttys in /etc/ttys and you enable user accounting. Then, the next time you boot into a kernel that doesn't have dci support, init or some other process will try and fail to read the enabled ttys, log something in /usr/adm/wtmp, if it exists, and then loop (very quickly), over and over and over. If you aren't paying attention, this will hardly be noticeable on modern hardware running simh, but I'm guessing this would have been disastrous, back in the day. The simple solution is to boot w/dci enabled when you have ttys enabled, and only boot w/o dci enabled when you have disabled the ttys. I'm guessing that this wasn't really ever an issue, back in the day, as folks prolly didn't just yank their dci's and reboot a different kernel? But, such are the joys of simulation. Anyhow, if this doesn't sound like a very likely or reasonable analysis of what was happening, I'd appreciate your letting me know, or if you've experienced something like it before, it'd be great to know that I'm not alone in this silliness. Will

2 years, 11 months

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TUHS January 2022