+# Overview #
+
+This directory contains a V5 UNIX system image for use with the PDP-11
+simulator included in SIMH. The image was taken from a PDP-11/45 with an RK05
+disk (2.4 MB).
+
+V5 UNIX was the first version licensed widely outside AT&T, largely due to
+[Thompson and Ritchie's CACM
+paper](https://www.bell-labs.com/usr/dmr/www/cacm.html) that had recently
+introduced UNIX to the world.
+
+Version 5 still only targeted PDP-11s, but expanded to include those models
+with an 18-bit physical address space, compared to the 16-bit address space of
+previous models. This allowed up to 256 kB of RAM and greatly increased the
+capabilities of the system, needed as UNIX reached "above 50" installations at
+the time of this release.
+
+This is the second release of UNIX written in C, a language still in flux that
+had only existed for a couple years. The system is self-hosting using the
+included compiler but there are many differences from modern C visible in the
+on-disk source code.
+
+Old enough to predate the Bourne shell from Steve Bourne, V5 UNIX ships with
+the Thompson shell written by Ken Thompson. This was the first UNIX shell,
+mainly a command interpreter rather than the interpreted language that most
+UNIX shells became. Intentionally minimal, commands like `if` and `goto` are
+implemented as separate executables rather than as built-in shell commands. This
+shell was replaced by the Bourne shell in V7 UNIX and by the C shell in 2BSD,
+leading to its rapid decline in popularity.
+
+Several now common commands were first introduced in this release, including
+`dd`, `pwd`, and `wump` (Hunt the Wumpus). At this stage it's starting to
+*feel* like a UNIX system.
+
+Then there's the editor, `ed`. A UNIX classic, it's a little like using `vi`
+with your eyes shut. If you've never used it before, check out my [guide to
+ed](https://subgeniuskitty.com/development/pdp-11/guide-to-ed-text-editor).
+
+
+# Status #
+
+Fully tested on SIMH 3.9-0.
+
+
+# Instructions #
+
+
+## Power On ##
+
+To power up a simulated PDP-11/45 and run this V5 UNIX disk image, simply
+un-gzip the disk image file and start up SIMH with the provided configuration
+file.
+
+ % gunzip unix_v5_rk.dsk.gz
+ % pdp11 simh.conf
+
+ PDP-11 simulator V3.9-0
+ Disabling XQ
+ .
+ .Type kernel filename at the '@' prompt.
+ .For example: @unix.
+ .UNIX username is 'root'.
+ .No password.
+ .
+ @
+
+The `@` prompt is from the bootloader, to whom we must pass a file to continue
+the boot process. Our kernel is a file named `unix`, so type that here followed
+by `ENTER`.
+
+ @unix
+
+ ;login:
+
+The system has now booted up and you may login as `root` (no password).
+
+ ;login: root
+ #
+
+That's it! V5 UNIX is up and you're logged in.
+
+
+## Power Off ##
+
+To power off, assuming you are logged in as `root` and the system is otherwise
+inactive, use the `sync` command to flush any buffers to disk and then type
+`Ctrl-e` to halt the simulation and `quit` to exit SIMH.
+
+ # sync; sync
+ # <Ctrl-e>
+ Simulation stopped, PC: 001726 (MOV (SP)+,177776)
+ sim> quit
+ Goodbye
+
+Note that you can also press `Ctrl-e` at any time and SIMH will halt the PDP-11
+simulation and drop to the `sim>` prompt where you can exit. However, doing
+this is likely to corrupt a disk as it is equivalent to yanking the power cord
+from the wall. To resume from the `sim>` prompt, simply type `go` and execution
+will resume from where it left off..
+
+
+## Transfer Files ##
+
+Output to the line printer or input/output via the paper tape are one option.
+The relevant options to enable that hardware in SIMH are commented out in
+`simh.conf`.
+
+When offline, it is possible to mount the disk image and interact with it
+directly. For example, use
+<https://git.subgeniuskitty.com/pdp11-unix-fusefs/.git>.
projects / simh-images / commitdiff