Using Multics

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This page contains a collection of topics on using Multics.

Logging In

Once you connect to a Multics system, you will see a prompt like this:

Multics MR12.6d: Gold Hill Multics (Channel d.h001)
Load = 5.0 out of 90.0 units: users = 5, 03/22/16  1517.4 pst Tue

You can type "help" here, in which you'll get a list of the most common commands available here:

Examples of correct login:
   login  Person_name projectid
   enterp Special_name projectid
   enter  Special_name projectid
Upper and lower case letters are different.
Check any typing conventions for your terminal.
Contact your administrator for more help.

Please try to login again or type "help" for instructions.

If you have an account on the system, you should use the "login" command to log in. For anonymous access, you can use either the "enter" or "enterp" commands. There are other options available at this prompt, including the "ttp" command, which will display your current "terminal type" or set your terminal type.

Logging into an Existing Account

To login, enter a command such as:

login Repair

You will be prompted for a the password for the "personid" Repair. If the password is correct, you will be logged in as "Repair" in whatever project is the default project for "Repair".

You can use "l" as a shortcut for "login".

For the first login to a cold-booted (or QuickStart) Multics system, the only interactive login accounts available are Repair.SysAdmin and Repair.SysDaemon. The password for the "Repair" personid is "repair". The first time you login as "Repair" you will be required to change the password.

l Repair
You must use the -change_password option to change your password.
Please try to login again or type "help" for instructions.

To change your password during login, use either the -change_password or -cpw control argument to the login command. You will be prompted for the old password, and (twice) for the new password.

l Repair -cpw
New Password:
New Password Again:
Password changed.
You are protected from preemption.
Repair.SysAdmin logged in 03/22/16  1648.8 pst Tue from ASCII terminal "none".

New messages in message_of_the_day:

Welcome to the Multics System.

print_motd:  Created >user_dir_dir>SysAdmin>Repair>Repair.value.
r 16:48 1.056 31

Note that the default project for Repair is SysAdmin. Repair is also registered on the SysDaemon project. You should refrain from logging in as Repair.SysDaemon, as users on the SysDaemon project have read/write access to virtually everything and can very easily damage the file system in ways that make it unbootable. Of course, there may be times when you need to login to this project.

If you don't want to login with the default project, you can specify another project during login:

Multics MR12.6d: Gold Hill Multics (Channel d.h000)
Load = 5.0 out of 90.0 units: users = 5, 03/22/16  1652.1 pst Tue
l Repair SysDaemon
You are protected from preemption.
Repair.SysDaemon logged in 03/22/16  1652.2 pst Tue from ASCII terminal "none".

New messages in message_of_the_day:

Welcome to the Multics System.

print_motd:  Created >user_dir_dir>SysDaemon>Repair>Repair.value.
r 16:52 1.253 21

Note that upon login, Multics will display a "ready message", indicating that it is ready for you to enter commands:

r 16:52 1.253 21

Logging in as an Anonymous User

if you don't have an account on a Multics system, the administrator may have enabled Guest logins. There are two kinds of Guest logins: those that require a password and those that don't. We will explore those without passwords here.

To login to Multics on the Guest project as an anonymous user, use the "enter" or "e" login command:

Multics MR12.6d: Installation and location (Channel d.h000)
Load = 5.0 out of 90.0 units: users = 5, 03/22/16  1736.5 pst Tue
enter Swenson Guest
You are protected from preemption until 17:36.
Anonymous user Swenson.Guest logged in 03/22/16  1736.6 pst Tue from ASCII terminal "none".

New messages in message_of_the_day:

Welcome to the Multics System.

print_motd: Entry not found. Attempting to update message-of-the-day information in default value segment.
r 17:36 1.151 20

You may use any Personid you like. I used my real Personid, above, but I really am logged in anonymously. You can verify this with the "who" command:


Multics MR12.6d, load 6.0/90.0; 6 users, 1 interactive, 5 daemons.
Absentee users 0/3

r 17:40 0.079 0

In this case, you will not have write access to your home directory (which will be >udd>Guest). If you wish to create files, you will have to use your process directory. Your process directory will have a pathname like:


You can use the command/active function "process_dir" or "pd" to determine your process directory. To change directories to your process directory, for example, use this command:

cwd [pd]
r 17:43 0.113 2

r 17:43 0.069 0

You will have write access to your process directory, where you can create, edit, etc. files. Note, however, that your process directory will be deleted upon logout. If you wish to have permanent file storage, either use a non-Guest account or ask your system administrator (which may be you!) to create a writeable home directory for Guest anonymous logins. See Giving Guest Users a Writeable Home Directory.

Getting Around

If you are like most of us, you haven't used Multics in decades.  :-) Or you might never have used Multics before. Probably the most important few things to learn immediately are these:

  1. To change working directories, use the "change_wdir" or "cwd" command. Do NOT use "cd", which, on Multics, is "create_directory".
  2. The pathname separator is ">" rather than "/" or "\".
  3. "ls -l", which on Linux gives you a "long" listing, will list only "links". You probably want "ls -a" which shows you segments, directories, multi-segment files (MSFs), and links.

When you first login, you will find yourself in your home directory. Your home directory is located under your project directory. And the project directory is located under the directory >user_dir_dir (or >udd). Your home directory will therefore generally have this form:


If user Personid is Swenson and your Project is SysAdmin, your home directory will (by default) be:


If you want to change directories to your project directory, you can use relative or absolute pathnames. Using absolute pathnames, you would type:

cwd >udd>SysAdmin

If your working directory is currently >udd>SysAdmin>Swenson, and you wish to change to the parent (Project) directory, you can use relative paths:

cwd <

Creating Directories

To create a directory, use the "create_dir" or "cd" command. For example:

cd exciting_project

Listing the Contents of a Directory

To list the contents of a directory, use the "ls" command. Note, however, that Multics, unlike most systems these days, will "ls" exactly what you ask it to. If you just type:

ls >udd>SysAdmin

it will dutifully show you:

ls >udd>SysAdmin

Directories = 1.

sma  SysAdmin

r 18:57 0.110 0

To list the contents of the >udd>SysAdmin directory, type:

ls >udd>SysAdmin>**

However, this is probably still not quite what you want, since typing that command will result in:

ls >udd>SysAdmin>**

r 18:58 0.225 1

This is because you didn't tell the "ls" command what you wanted to list, and it, by default, only shows you segments, and if there are none, gives you the totals of all the various "entry" types.

To see everything under the >udd>SysAdmin directory, use this:

ls >udd>SysAdmin>** -a

Directories = 4.

sma  admin
sma  library
sma  Repair
sma  SA1

r 18:01 0.215 0

This shows you that under this directory, there only exist directories.

Entry Names

Each directory entry name (e.g. segments, directories, MSFs, and links) can have 1 or more names. The first name is typically called the "primary name" and the other names are called "addnames". In the example, above, you can see that the "admin" directory has an "addname" or "a" and the "library" directory has two addnames: "lib" and "l".

To add a new name to an entry, use the "add_name" or "an" command. For example:

cd foo
r 18:03 0.041 1

an foo bar
r 18:03 0.077 3

ls foo

Directories = 1.

sma  foo

r 18:03 0.065 0


When get a new process, either by logging in or executing the "new_proc" command, by default, Multics will look for and execute your start up script, called The "ec" stands for "exec_com", which is the scripting language available on Multics. Process initialization looks for this script in your home directory. If it doesn't find one there, it looks in your project directory, and if it doesn't find one there looks in >system_control_1>

If it finds a, it executes it, passing it two parameters. The first parameter is either "login" or "new_proc". While many scripts ignore their parameters, these can be used to differentiate between the two ways you can get a new process. The second parameter is either "interactive" or "absentee". Interactive processes are those attached to a terminal and initially created through a login. Absentee processes are background processes that you can schedule. You do not need to be logged in interactively in order to have absentee processes running on your behalf.

Unless you or someone else has created a for you in your home or project directory, the system will execute the found in >system_control_1> The contents of this segment are shown below:

pr >sc1>

                   03/22/16  1812.0 pst Tue

&  ******************************************************
&  *                                                    *
&  * Copyright, (C) Honeywell Bull Inc., 1987           *
&  *                                                    *
&  * Copyright (c) 1972 by Massachusetts Institute of   *
&  * Technology and Honeywell Information Systems, Inc. *
&  *                                                    *
&  ******************************************************

&   1) change(87-08-12,GDixon), approve(88-08-15,MCR7969),
&      audit(88-08-03,Lippard), install(88-08-29,MR12.2-1093):
&      Change to call print_motd instead of using the print command to print
&      the message of the day. (phx15921)
&                                                       END HISTORY COMMENTS
& -- default start_up for >sc1
& this exec com just prints the motd to duplicate the old behavior of
& process_overseer_.
& It is executed by all users (with standard process overseers) who
& lack in their homedir and project dir.
&command_line off
&goto &ec_name

&label start_up
&if [equal &1 login] &then print_motd

r 18:12 0.449 0

You will notice that this uses "&1" to access the first parameter ("login" or "new_proc"). In this case, it only prints the message of the day ("print_motd" or "pmotd") upon login, and not for new_proc.

The second thing you may notice is the contruction:

&goto &ec_name

Any exec_com can have multiple "addnames" on it. This &goto command will transfer control to the "&label" whose name is equal to the name used to invoke the exec_com. This allows you to group multiple exec_com scripts into one segment and branch to the correct one depending on which name was used to invoke it. Of course, to make this work, you must add names to the segment for each of these "entrypoints".

For info on exec_com syntax and functionality, type "help exec_com" or see the documentation on "exec_com" in the "Commands and Active Functions" manual, AG92.

A More Useful

Below, you will find another example of a

&version 2
&trace &command off
&- Enable abbreviations in commands
&- Add >doc>privileged to your info search paths
    asp info >doc>privileged
&- Make C compiler accessible/usable
    asr >sl3p>c_compiler>e
    asp info >sl3p>c_compiler>info
&- For interactive logins:
    &if [equal &2 interactive] &then &do
&-    Set terminal type;
          stty -ttp vt102_PL50
&-    And invoke video system.
          wdc invoke
&-    On systems with several users registered:
&-      - Accept interactive messages
&-      - Check for mail/messages

The comments in the above explain what the corresponding commands do. Note that this exec_com starts with "&version 2". This enables the "new" (version 2) functionality of exec_com. As you can guess, there was a more limited "version 1" before the "new" version. (Yes, I mean "new" in the 1980s). See the documentation on "exec_com" for details.


When you login, the command processor (command_processor_$command_processor_) evaluates command as you type them on your terminal. You can enable an alternate command processor, abbrev$abbrev_processor that expands abbreviations in your command lines before passing them to command_processor_$command_processor_. You enable "abbrevs" by typing the "abbrev" command, or, more practically, by putting the "abbrev" command in your

To add an abbrev, you use a command like the following:

.ab cd format_line "You really don't want to type 'cd' do you?"

This defines an abbrev called "cd" that, when typed at the beginning of the line (".ab" rather than ".a") will expand to the command:

format_line "You really don't want to type 'cd' do you?"

format_line is a command and active function that will format a string (with substitutions) and display it on the terminal (or return it as a string when invoked as an active function).

To list your abbrevs, use the ".l" command:

To execute a command without expanding abbrevs, preface the command with ". " (that is, a "." followed by a SPACE).

For more information on abbrev, type "help abbrev"

Editing Files

You have multiple editors available to choose from on Multics. Here is a list of a few:

  • Emacs
  • qedx
  • edm
  • Teco


Emacs is, well, Emacs. If you don't know what Emacs is, or how to use it, you are one very sad individual. Of course, the Emacs that you probably know and love is a lot more feature rich than the one on Multics. But yes, Emacs is written in MacLisp and runs quite well.

You invoke emacs with the "emacs" command, and exit it with the Control-x Control-c key binding. For help with emacs, type "help emacs" (outside of emacs). You can type Escape-x help <CR> inside emacs for some brief help and pointers to more documentation. Of course, you can also learn lots more about Emacs by reading the various Multics Emacs manuals.

If you haven't set your terminal type (see "help stty") then emacs will prompt you for a terminal type upon startup. Assuming you are connected to Multics via telnet, answer "vt102" if you haven't set up any better terminal types.

I have an abbrev I use to invoke emacs:

.ab emacs emacs -ttp vt102 -ll 132 -pl 50 

This tells emacs to use the "vt102" terminal type and to set the line length to 132 characters and the page length to 50 characters.

You can also invoke emacs after first invoking the "video system" ("wdc invoke").


QEDX is a simple non-WYSIWYG editor. Do a "help qedx" for help or see the documentation on QEDX in the "Commands and Active Functions" manual, AG92.

As a simple example, to create a new file with the contents:

&version 2
&trace &command off
&print hello there

You could do the following:

&version 2
&trace &command off
&print hello there

The "a" command puts you in append mode. The following lines up to the "\f" are the desired contents of the segment. The "\f" command ends input. The "w" command saves the contents of the edit buffer to a segment whose name is specified as the argument to the "w" command. And the "q" command quits qedx.

Other useful commands are:

  • i - insert mode (inserts above the current position in the edit buffer)
  • a - append mode (inserts below the current position in the edit buffer)
  • s/XXX/YYY/ - substitutes YYY for XXX in the current line
  • r - reads in a segment


This editor is like qedx. Do a "help edm" for details.


I'm not going to touch this with a 10-foot pole. Only crazy hackers use Teco. (By the way, the first Emacs i ever used was written in Teco. And you wrote customizations to Emacs in Teco. I learned Teco so that I could customize Emacs. Thank goodness Emacs was rewritten in MacLisp.

If you really want to use Teco, do a "help teco" or see the documentation on this editor in the manuals.

Getting Help

All the commands and active functions, as well as many (most/) of the subroutines are documented online in what are called "info segments". These are text files so you can read them into Emacs or display their contents with the "pr" command. However, a much more useful command is "help", which will look for an info segment of the specified name (e.g. "help abbrev") and prompt you to display the various parts of the documentation. Try it.

If you are trying to locate an info segment, but don't know its name, try the "list_help" or "lh" command. This will display the names of all the info segments whose names include the substring you provide as a parameter to "lh".

Command Levels and Errors

When you first login, the system responds with a "ready" message. This "ready" message looks like this, by default:

r 18:54 2.000 90

To find out how to customize it, type "help general_ready" or "help gr". You can also find more info with "lh ready".

When you get an error, a "condition" is signaled and a recursive command level is entered. The ready message shows this in the following way:

r 18:56 0.097 0 level 2

The number after "level" is the depth of the command levels. You can also get to a new command level, interrupting the executing program, by pressing the Control-c command. Doing so causes Multics to display:

r 18:57 0.068 0 level 3

To throw away the current program execution (stack frames), you can use the "release" or "rl" command. To release all recursive command levels and return to level 1, you can type "rl -all".

If you have interrupted a program (with Control-C) and wish to resume it, use the "start" or "sr" command.

As an example of a signaled condition causing a recursive command level, consider the following PL/1 program:

pr foo.pl1

                    foo.pl1   03/22/16  1900.7 pst Tue

foo: procedure options(variable);

   dcl a fixed bin;
   dcl b fixed bin;

     a = 10;
     b = a/0;
end foo;

r 19:00 0.148 0

If you compile this program:

pl1 foo.pl1
PL/1 33e
r 19:01 0.272 13

and run it:


Error:  Attempt to divide by zero at >user_dir_dir>SysAdmin>Repair>foo|11 (line 7)
(while in operator divide_fx1)
system handler for error returns to command level
r 19:01 0.168 0 level 2

you will get a recursive command level.

If you try to "start" this command,


Error:  Attempt to divide by zero at >user_dir_dir>SysAdmin>Repair>foo|11 (line
\c 7)
(while in operator divide_fx1)
system handler for error returns to command level
r 19:02 0.204 0 level 2

You will not be able to and will be returned to the current command level. To release this command level, do:

r 19:02 0.022 0

What To Do If You Get an Unexpected Error

If you do get a recursive command level due to an error that you don't think is your own fault and can't otherwise explain -- especially if you think it is due to an simulator error -- you can invoke the "probe" command, and within "probe", the "stack" ("sk") command to get a bit more info as to the cause of the error. See below:


Error:  Attempt to divide by zero at >user_dir_dir>SysAdmin>Repair>foo|11 (line
\c 7)
(while in operator divide_fx1)
system handler for error returns to command level
r 14:57 0.250 0 level 2

Condition zerodivide raised at line 7 of foo (level 4).
 11          command_processor_
 10          release_stack
  9          unclaimed_signal
  8          wall
  7          any_other.2
  6          wall                                          error
  5          any_other.2
  4          foo (line 7)                                  zerodivide
  3          command_processor_
  2          listen_
  1          initialize_process_

As you can see, the zerodivide condition was raised as a result of the code at line 7 in the "foo" executable, which was invoked from the command_processor_. You can exit out of "probe" with the "q" command or hunt around for more info.

You can also use the "trace_stack" ("ts") command to trace the stack after an exception. See below for example output:

system handler for error returns to command level
Machine conditions not available.

234|5160    default_error_handler_$wall|2671 (bound_error_handlers_|2671)
  Cannot get line number in default_error_handler_
  2671   000622700100     tsx0    pr0|622 call_ext_out_desc
  Argument list pointer: 234|5136
          No arguments.

234|5060    initialize_process_$any_other.2|426 (bound_process_init_|426)
  Cannot get line number in initialize_process_
   426   000617700100     tsx0    pr0|617 call_ent_var
  Argument list pointer: 234|5006
          ARG  1: 234|4160 stack_4|4160
          ARG  2: "zerodivide"
          ARG  3: 77777|1 null pointer|1
          ARG  4: 77777|1 null pointer|1
          ARG  5: "0"b

234|4520    signal_$signal_|1467 (bound_library_1_|11205)
  Cannot get line number in signal_
 11205   000616700100     tsx0    pr0|616 call_ent_var_desc
  Argument list pointer: 234|4246
          Warning: arg 1 packed mismatch: 0 supplied, 1 expected.
          ARG  1: "zerodivide"
          ARG  2: 234|4160 stack_4|4160
          ARG  3: 77777|1 null pointer|1
          ARG  4: 77777|1 null pointer|1

234|4100    return_to_ring_0_|0
          Bad argument pointer.
          on "cleanup"  call restart_fault|1

Attempt to divide by zero at >user_dir_dir>SysAdmin>Repair>foo|11 (line 7)
(while in operator divide_fx1)  (zerodivide condition)
  foo.pl1 (line 7): b = a/0;
    11   001262700100     tsx0    pr0|1262 divide_fx1

Machine registers at time of fault

pr0 (ap)  234|3760            stack_4|3760
pr1 (ab)  234|3734            stack_4|3734
pr2 (bp)  374|17              foo|17
pr3 (bb)  234|3640            stack_4|3640
pr4 (lp)  247|54376           !BBBKKPFblfpMpH.area.linker|54376  (linkage|0 for
\c foo)
pr5 (lb)  247|4052            !BBBKKPFblfpMpH.area.linker|4052  (internal stati
\cc|0 for init_vol_header_)
pr6 (sp)  234|3640            stack_4|3640
pr7 (sb)  234|0               stack_4|0

x0     12   x1      0   x2     66   x3  26724
x4     21   x5      2   x6      0   x7  26362
a 000000000000  q 000050000000  e 0
Timer reg - 41477, Ring alarm reg - 0

SCU Data:

  4210    400257050040 000000000035 400234000000 000000000000
          026731400200 003776000000 000016507100 200000371502

Divide Check Fault (35)
By: 257|26731 pl1_operators_|6421  (bound_library_wired_|26731)
Referencing: 234|3776 stack_4|3776
On: cpu a (#0)
Indicators:  zero, ^bar
APU Status:  sd-on, pt-on, fap
  4216   0 00016 5071 00      dvf       pr0|16
  4217   2 00000 3715 02      epp5      pr2|0,qu

Time stored: 03/23/16  1457.1 pst Wed (147262037442100574)
Ring:          4

234|3640    foo$foo|11  (line 7) in operator divide_fx1
  foo.pl1 (line 7): b = a/0;
    11   001262700100     tsx0    pr0|1262 divide_fx1
  Argument list pointer: 234|3206
          Command name: foo
          No arguments.

234|2700    command_processor_$command_processor_|2101 (bound_multics_bce_|2101
  Cannot get line number in command_processor_
  2101   000623700100     tsx0    pr0|623 call_ext_out
  Argument list pointer: 234|2564
          ARG  1: 234|2640 stack_4|2640
          ARG  2: 4
          ARG  3: 0
          on "command_abort_"  call command_processor_|1140 (bound_multics_bce_

234|2400    listen_$listen_|554 (bound_command_loop_|34522)
  Cannot get line number in listen_
 34522   000623700100     tsx0    pr0|623 call_ext_out
  Argument list pointer: 234|2242
          ARG  1: "exec_com >user_dir_dir>SysAdmin>Repair> new_proc 
          on "cleanup"  call listen_|271 (bound_command_loop_|34237)

234|2000    initialize_process_$initialize_process_|704 (bound_process_init_|70
  Cannot get line number in initialize_process_
   704   000616700100     tsx0    pr0|616 call_ent_var_desc
  Argument list pointer: 234|0
          No arguments.
          on "any_other"  call initialize_process_|411 (bound_process_init_|411

End of trace.

r 14:58 2.000 4 level 2

Any information that you're willing to post to the relevant mailing list to help us find and fix simulator bugs would be greatly appreciated. Use the mailing list to report such errors.

Printing Files

In order to queue a segment for printing, use the "enter_output_request" ("eor") command. For help on this command, type "help eor". Segments queued for printing will be printed when the printer becomes idle, as long as the printer daemon is running. After a cold boot of Multics, or when running the QuickStart, there is one printer daemon configured for the device "prta". However, unless you specifically start the daemon, no printer requests will be served. To start the printer daemon, you can use the Initializer command:

x io

This will send the appropriate commands to the IO.SysDaemon (prta) daemon to begin processing requests from the queue.

Note: the "old" way to queue a segment for printing was to use the "dprint" ("dp") command. While this command still works, it has been functionally replaced with the preferred "enter_output_request" command.

DPS8M Specific Info

The DPS8M simulator supports the printer devices (e.g. prta) creating files on the host system, in the directory where you started the simulator (e.g. in the QuickStart_MR12.6f directory). The file will have a filename following the pattern: <device-name>.spool.<request-id>.<personid>.<projectid>.<tag>.<random-string>. For example:


The simulator doesn't actually print the file for you, it just creates it. You are free to "print" it any way you'd like. One option is to use the "enscript" program to convert the "lineprinter" output to a PDF, and then use your operating system facilities for printing the PDF.

Shutting Down Multics

You shut down Multics by entering commands on the operator console. First, get the attention of the Initializer process by typing the Esc key. The operator console should respond with:


Then, log out all the daemons:

M-> logout * * *


Press the Esc key to "give up the console" so that the Initializer process can logout all the daemons. If you don't press Esc, you'll have to wait a bit before the console times out.

You should see output similar to this:


 1603  as   LOGOUT             IO.SysDaemon.z dmn cord   0: 0 $0.02 (looc)
 1603  as   LOGOUT             Backup.SysDaemon.z dmn bk   0: 0 $0.03 (looc)
 1603  as   LOGOUT             IO.SysDaemon.z dmn prta   0: 0 $0.02 (looc)
 1603  as   LOGOUT             Utility.SysDaemon.z dmn ut   0: 2 $1.82 (looc)
 1603  as   LOGOUT             Volume_Dumper.Daemon.z dmn vinc   0: 0 $0.03 (looc)

Give the system a few seconds to log out all the daemons, and then shut it down (remember to type Esc to get the attention of the operator console):

M-> shut

 1605  as   act_ctl_: shutdown, 5 0.02 0.02 0.00 1.22 0:0:3 $1.91
1605.9  shutdown complete
DBG(6122232634591)> ERR ERR: Need status register data format
DBG(6122232634639)> ERR ERR: doPayloadChan expected IDCW 10 (12)
bce (boot) 1605.9:

Multics is now shut done, however, you have not yet exited from the Bootload Command Environment (BCE) to the simulator. Press Esc again to get the operator console's attention and issue the "die" command, confirming with "y":

M-> die

Do you really wish bce to die? M-> y

BCE DIS causes CPU halt

simCycles = 6122989885622

cpuCycles = 491386437
Timer runout faults = 2332
Derail faults = 1
Lockup faults = 65
Connect faults = 1656
Illegal procedure faults = 5
Directed fault 0 faults = 584
Directed fault 1 faults = 6576
Access violation faults = 267
Fault tag 2 faults = 2301

Halt, IC: 000012 (000000000000)

You have been returned to the simulator's prompt. You may exit the simulator with:

sim> quit

You are now back at your terminal (shell) prompt.

Command Line History and Editing in Video System

One of the most useful features of MR12.6f, courtesy of Gary Dixon, is the new input_history (ih) command. This command, intended to be used with the video system, allows you to recall previously entered commands and input, search for previous input, and edit input using Emacs-like keybindings. For detailed documentation, while logged in, use the "help input_history" command.

To help you get started, perform the following steps:

  • make sure you set your terminal type to an entry that supports the video system (see below)
  • start the video system with "wdc invoke"
  • start input_history with "ih attach"

Now, type a few commands at the command processor. Then, use Control-P to recall your previous input, and Control-N to move toward more recent input. Use Control-R to search backward in your input history for a string (to find a previous command).

Use Control-A to go to the beginning of a line, and Control-E to go the end of the line. Control-F moves forward a character and Control-B moves backward. Control-D deletes forward a character, and Escape-D deletes forward a word. Escape-F moves forward a word, and Escape-B moves backward a word. There are lots of other key bindings for editing lines -- see the input_history (ih) help file as well as the video system help ("help").

Terminal Types and the Video System

In order to use the video system, you need to set your terminal type to one of the terminal types that supports the video system. If you are simulator user, any of the VT102 terminal types will work, but if you want a larger screen than 24 lines by 80 columns (the default), you should choose a terminal type such as VT102_132C_50L, which gives you a 50 line by 132 column, VT102-compatible terminal type. Many terminal simulators today support VT102 (or VT100) compatibility and, therefore, will work fine with this terminal type.

The Terminal Type Table (TTT) and the source file for this binary table, the TTF (>udd>SysAdmin>a>TTF.ttf) define the terminal types available to you on your system. If your system is a newly-installed MR12.6f system, you will have the VT102_132C_50L terminal type defined. If your system is running an older release, or was upgraded from an older release, you may have to merge the new VT102_132C_50L terminal type into your TTF, rebuild the TTF (cv_ttf TTF) and install the new TTT (install TTF.ttt) in order to use it.

If you look through the TTF, any entries that define a "video_info" section are compatible with the video system. Choose one of these terminal types (or VT102_132C_50L if you have it). Set your terminal type thus:

stty -ttp vt102_132c_50l

Now that your terminal type is set, you can invoke the video system with:

wdc invoke

Search Rules and Search Paths

There are two mechanism Multics uses to find executables or other segments based on rules you can defined (and system defaults): Search Rules and Search Paths

Search Rules

Search rules are a list of directories that are searched to find a command, subroutine, or data item referenced symbolically. Each directory is examined, in order, to find the given external name. Search rules are not used when a segment is addressed by its pathname, which explicitly specifies the directory containing the segment.

Default search rules are defined by the system administrator and these can be overridden by users with the add_search_rules (asr), delete_search_rules (dsr), and set_search_rules (ssr) commands. You can display your search rules with the print_search_rules (psr) command.

See the help files for these commands for more details and consult the documentation for greater depth. Special search rules names include initiated_segments, referencing_dir, working_dir, process_dir, and home_dir. Read about these in the help segment for add_search_rules.

Search Paths

While search rules are used to find executable segments, search paths are used to find other types of segments, including info segments, include files, compose macros, exec_coms, forums, etc. In fact the set of search paths is extensible to new kinds of segment.

Search paths are manipulated with the following commands: add_search_paths (asp), delete_search_paths (dsp), print_search_paths (psp), set_search_paths (ssp), and where_search_paths (wsp). See the help files for these commands for more info or consult the Multics documentation set.

As an example, when you invoke an exec_com with a command such as "ec foo", Multics uses the exec_com search paths to locate your exec_com. To determine your current exec_com search path, you could use this command:

psp exec_com

r 08:45 0.068 0

This means that Multics will first look in your working directory and then in >udd>SysAdmin>Swenson>exec_com.

More Processing

Whether you are using the video system (do "help" for more help on the video system) or not, Multics, if it knows about your terminal type and believes that it is a video terminal, will perform "more processing'. When output reaches the bottom of the screen, it presents a prompt (EOP iwhen not in the video system, and "More? (RETURN for more; DEL to discard output.)", when in the video system), and waits for you to hit Return or Enter to display the next page.

More processing is controlled by a TTY mode called "more". You can disable more processing temporarily with "stty -modes ^more" and turn it back on with "stty -modes more". The terminal type you have chosen will define the number of rows and columns, and the number of rows determines when more processing occurs. If you don't like where Multics is paginating, change your TTY type. To find out your current TTY type, do this:

stty -pr
Type: VT102_132C_50L
Modes: more_mode=scroll,more,ll=131,pl=49,^vertsp,can,erkl,esc,^rawo,^red,^ctl_char,^edited
r 08:52 0.057 0

You can see from the above example, that the page length (number of rows) is represented as "pl=49", meaning there are 49 rows (1 row is reserved for the more prompt, so this is a 50-line display). You can set your terminal type with the "stty -ttp xxx" command. For more help, see the info segment on the set_tty (stty) and print_terminal_types (ptt) commands, and or get general info on TTY modes by typing "help".

Per Process Time Zone Setting

If you would like to change the time zone for just your own process (as opposed to the whole Multics system), the set_time_default (std) command will let you do this. To set your local time zone to "est" do the following:

std zone est