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Incompatible Timesharing System

About ITS

ITS, the Incompatible Timesharing System, is an operating system for the PDP-10 computer family. It was created by hackers at MIT in the 1960s. The MIT site was shut down in 1990, but enthusiasts continue to operate ITS systems to this day.

Some notable ITS features:

Hosted the first versions of Emacs, Zork, Macsyma, Maclisp, Scheme, and multi-player Maze War
Virtual memory
User-space device drivers
Networking: TCP/IP, ARPAnet, Chaosnet
Transparent network file system
Terminal-independent text output
Graphical workstations

There is a mailing list for discussion about ITS. Go to http://its.victor.se/mailman/listinfo/its-hackers_its.victor.se for more information.

About this project

This repository contains source code, tools, and scripts to build an ITS system from scratch.

The goals are:

To provide an automated build from start to end. No user intervention is necessary.
To check which programs have source code, and which programs are missing source code.
To ensure that we know how to build all programs.
To update programs with the latest bug fixes and enhancements.
To be able to set configurable options across the whole system, such as host name, IP address, hardware devices.

The build currently runs on the SIMH and KLH10 emulators. Of course, we'd be delighted to test this on a real KS10.

Building

To build ITS with this repository, you need some tools installed; see the table below. Ensure all submodules are checked out, and then type make EMULATOR=simh, make EMULATOR=pdp10-ka, make EMULATOR=pdp10-kl, make EMULATOR=pdp10-ks, or make EMULATOR=klh10. This will leave built files in the out directory, some of which are disk images with ITS installed.

Emulator	Dependencies
klh10	git, c compiler, make, expect, curses, autoconf
simh	git, c compiler, make, expect, curses, autoconf, sdl2
pdp10-ka	git, c compiler, make, expect, curses, autoconf, sdl2, sdl2-image, sdl2-net, gtk3
pdp10-kl	git, c compiler, make, expect, curses, autoconf, sdl2, sdl2-image, gtk3
pdp10-ks	git, c compiler, make, expect, curses, autoconf, sdl2

Usage

To start ITS, type ./start. If you see KLH10#, type go and Enter. If you see the DSKDMP prompt, type its, press Enter, and then <kbd>ESC</kbd><kbd>G</kbd>. If you use the pdp10-kl emulator there is no prompt and you need to type <kbd>ESC</kbd><kbd>L</kbd> ITS, press Enter, and then <kbd>ESC</kbd><kbd>G</kbd>. Eventually, you will see SYSTEM JOB USING THIS CONSOLE. You are now ready to log in, so type <kbd>CTRL</kbd><kbd>Z</kbd>. See doc/DDT.md for a list of useful commands.

Alternatively to logging in directly in the system console window, which will always be displaying daemon messages, you may prefer to use a seperate terminal session for logging in. To do this just run telnet localhost <port> from another shell window and press <kbd>CTRL</kbd><kbd>Z</kbd> to log in there. The port should be determined as per this list:

Port	Type	Emulator
10000	TK10	pdp10-ka
10002	Datapoint kludge	pdp10-ka
10003	Morton box	pdp10-ka
10004	DZ11	simh, pdp10-ks
10007	DTE2	pdp10-kl
10008	DL10	(pdp10-kl in the future?)

To shut down ITS, type :lock and then 5down. Log yourself out to avoid the 5 minute grace period: type :logout. When ITS writes SHUTDOWN COMPLETE, it's safe to stop the emulator. Press <kbd>CTRL</kbd><kbd>\</kbd> to escape to the simulator command prompt and quit to close it. If you had a separate telnet user session running you can similary press <kbd>CTRL</kbd><kbd>[</kbd> and then exit telnet.

ITS can optionally use some additional peripheral devices. To attach a simulated GT40 graphics terminal, type ./start gt40. If you run the KA10 emulator, you can use the Knight TV raster display by typing ./start tv11 tvcon. On a TV, type <kbd>F1</kbd> instead of <kbd>CTRL</kbd><kbd>Z</kbd>.

Here is an overview of the repository:

bin - PDP-10 binary files necessary to bootstrap the system.
build - build scripts.
conf - configuration for building ITS.
doc - documentation, most of which appear in the INFO system.
src - source code for ITS and all programs.
tools - build tools.
out - build output.
user - optional user files installed in ITS.

Terminal Emulators

Several emulators for terminals and peripheral processors are built along with ITS. They can be started conveniently with the start script, or separately. Not all terminal emulators are set up to work with all PDP-10 emulators by default.

Name	Description	Type	klh10	pdp10-ka	pdp10-kl	pdp10-ks	simh
type340	Type 340	vector	no	yes	no	no	no
gt40	GT40 PDP-11	vector	no	yes	no	yes	yes
imlac	Imlac PDS-1	vector	no	yes	no	no	no
simh_imlac	Imlac PDS-1	vector	no	yes	no	no	no
tv11	Knight TV PDP-11	cpu	no	yes	no	no	no
tvcon	Knight TV console	raster	no	yes	no	no	no
datapoint	Datapoint 3300	text	no	yes	no	no	no
vt52	VT52	text	no	yes	yes	yes	yes
tek	Tektronix 4010	vector	no	yes	yes	no	no

Documentation

See the doc subdirectory for documentation.

There are some short introductions for beginners:

A list of known ITS machines.

How ITS is built.

Applications

Some major applications:

Adventure, game
C10, C compiler
CLU, progamming language.
DDT, debugger
Emacs, editor
Logo, interpreter
Mac Hack VI and Tech II, chess programs
Maclisp, interpreter and compiler
Muddle, interpreter
Macsyma, symbolic math
Maze War, game
Midas, assembler
Muscom and musrun, for playing music
PDP-11 simulator
Scheme, interpreter
Spacewar!, game
Stanford University Drawing System
TECO, editor
TOPS-10 and WAITS emulator

There is a detailed list of all installed programs.