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The text below was keyed in by hand. To the best of my proofreading ability and understanding of HTML, it is a precise copy of the original 1963 memo, faithfully reproducing the exact places where TJ-2 inserted spaces for justification, with the following provisos:
Normal text; text that is underlined in the original.
¯X
would print as an overbar directly above the X, like the
"macron" diacritical mark. Whereever you see this sequence it should
be understood that in the original the overbar is printed directly above
the character that here is shown as following it.
PDP-1 COMPUTER [1]
MASSACHUSETTS INSTITUTE OF TECHNOLOGY
CAMBRIDGE 39, MASSACHUSETTS [2]
PDP-9-1
TJ-2 [3]
TYPE JUSTIFYING PROGRAM [4]
May 9, 1963
TJ-2 accepts English text from typewriter or reader, [5]
and reproduces it at any line length via typewriter and/or
punch. So much as possible both left and right margins are [6]
aligned in the output. To accomplish this the program
doubles some of the spaces in the output line, and may
hyphenate words, getting hyphenation data from its diction-
ary or from the operator via the display.
Normal Mode: All hyphens in the input text are assumed [7]
to mark compound words, and will be reproduced in the
output. Carriage return is treated as a space, except: (a) [8]
a string of carriage returns is ignored immediately follow-
ing a hyphen; (b) non-ignored carriage returns are translat-
ed into the same number of carriage returns if they
immediately precede a tab. Any number of adjacent spaces is
treated as a single space. Backspace and the unused Concise [9]
codes are illegal. The program simulates tabs by spacing to
the nearest imagined tab stop, as determined from the Test [10]
Word.
Quote Mode: The justification process may be sup-
pressed for a portion of the input by the appearance of "¯q" [11]
(overbar-q) which puts TJ-2 into the Quote Mode. Subsequent
characters from the input are copied exactly into the output [12]
until the occurrence of "¯e". It is wise to have carriage [13]
returns as the first and last characters in the quoted
material. All 100 octal Concise codes are legal in the
Quote Mode, but overbar should be used with great caution
because it is a signal for some special action by the
program.
Centering Mode: At the appearance of "¯c" the text up
to the next carriage return is centered on a separate line
in the output. Should quoted material appear in the text to
be centered, it is reproduced in the output but is not
counted for the centering process.
Figure Mode: The sequence overbar, f, a decimal
number, overbar, is taken by TJ-2 as a command to leave
blank lines for a figure in the output. The number given,
minus one, blank lines are inserted in the output immediate-
ly if there is room on the current output page, otherwise
the space is left at the beginning of the next page. If the
"f" is omitted, the space is always left immediately.
Inverted Indenting Mode: This mode is entered by the
occurrence of "¯i". A counter c is set to zero when the ¯i is
encountered. While in the Inverted Indenting Mode all input
lines not preceded by a multiple carriage return are
indented c tab stops in the output. Each line in the input
which is preceded by a multiple carriage return is preceded
by that many carriage returns in the output. Also it is
indented in the output by as many tab stops as in the input,
and it sets c equal to that number of tabs plus one. The
normal paragraphing mode is restored by "¯n".
Quoted Overbar: An overbar is copied into the output
if ¯/ (overbar-slash) appears in the input.
The following describes usage of the Sense Switches. [14]
Sense Switch 1: on -- input from typewriter [15]
off -- input from reader
Sense Switch 2: on -- output to typewriter [16]
off -- no typed output
Sense Switch 3: on -- output to punch
off -- no punched output
Sense Switch 4: on -- prohibit hyphenation
off -- allow hyphenation as per dictionary
or display.
Sense Switch 5 used by individual error halts
Sense Switch 6 turn on at end of run to indicate no
further input
The Test Word is divided into four fields, with use as
follows:
Bits Meaning
11-17 length of justified line
7-10 output tab spacing (equal, starting at left margin)
1-6 number of lines per page (0 means no pagination)
0 if on, stop after current output page.
To hyphenate a word that appears on the display, point [17]
the light pen at the + figure between letters; it will [18]
become a small =. If an erroneous + was hit, all = marks
can be restored to + by penning the "OOPS" dot. When all [19]
the satisfactory hyphenation-points are marked, pen "SAVE"
to preserve the word in the dictionary or "FORGET" to accept [20]
the hyphenation but not to retain it. (There will be no
SAVE dot if the dictionary is full.) The Console version of [21]
TJ-2 starts with a blank dictionary.
Error halt aspects, indications, and recovery proced-
ures are tabulated below.
AC IO Meaning SS5 down, SS5 up, [22]
Continue Continue
-0 0 output line too insert carriage (likewise) [23]
long return
+0 +0 run completed start new run (likewise)
1 char illegal Concise ignore accept
code
2 char illegal parity ignore accept
3 0 word too long forget word insert space
4 ... word to be hyphen- take it anyhow don't hyphenate
ated ends in non-
spacing character
6 page end of output continue (likewise)
no. page
10 ... dictionary full clobber program don't save [24]
12 ... too much stretch- stretch as much don't stretch
ing needed as possible
17 ... TW calls for very start over accept
short line
Was TJ-2 a word processor?
TJ-2 does not resemble modern word processors with "on-screen formatting" or "WYSIWYG editing." It somewhat resembles earlier word processors like RUNOFF, TROFF or WordStar in which the editor and formatter are separate. Comparing TJ-2 to contemporary "word processors," TJ-2 had:
Notice that none of the following terms are used anywhere in the memo: application, document, editor, font, format, software, text, word processor, word wrap.
(I first encountered the term "word processing" in an IBM advertisement of the mid-seventies, where the term was understood to encompass manual typewriters and dictating machines as well as magnetic-card Selectrics).
The general writing style of the memo is similar to that, e.g. of the Digital PDP-1 Handbook. The capitalization of terms such as Test Word, Indented Text Mode, etc. is similar to that in the PDP-1 Handbook, which contains phrases such as "the Light Pen status bit is set to one," "the contents of the extended Program Counter in bits 2 through 17," etc.
[1] PDP-1 COMPUTER:The memos in this series were all attributed simply to the "PDP-1 COMPUTER." In actuality, they were produced at a facility on the second floor of Building 26, which comprised two large rooms containing the one-of-a-kind TX-0, originally built by MIT, and a commercially built PDP-1, donated by Digital Equipment Corporation. The PDP-1 was used as an experimental testbed by the Electrical Engineering department for experiments in timesharing, and was also generally available to undergraduates. Back
[2] CAMBRIDGE 39, MASSACHUSETTS: The United States Post Office introduced zip codes about a year after this memo was written. Back
[3] TJ-2:" I don't know if there ever was a TJ-1. Back
[4] The title line, "TYPE JUSTIFYING PROGRAM," is underscored in the original. Back
No name is credited as either author or programmer. The program was demonstrated to me by Pete Samson. It was my impression that he wrote it but others may have contributed.
This memo was obviously produced with TJ-2, but most of the other memos in the same series were not. Back
[5] I've tried to duplicate the precise locations at which TJ-2 placed spaces, hyphens, etc.
"Typewriter:" the PDP-1 console typewriter. This was an IBM electric typewriter to which a company called Soroban Engineering had added switches and solenoids capable of sensing and initiating keystrokes.
This IBM typewriter was a traditional design with typewriter-style typebars (not a "golfball" Selectric). As was customary in typewriters, each typebar carried a pair of characters, one uppercase and one lowercase. The shift key raised or lowered the entire heavy type basket, selecting which of the two characters struck the ribbon. The Soroban mechanism was quite unreliable, and, in particular, often missed a case shift. However, it provided what in eighties terminology would have been called "true letter quality" printing. An additional feature of this unit was a two-color red-and-black ribbon. The PDP-1 debugger, for example, printed user commands in black and debugger responses in red.
"Reader:" high-speed 400 "line"/second photoelectric punched paper-tape reader.
"Punch:" 63 character/second paper tape punch manufactured by Teletype. Back
[6] The period ending a sentence is always followed by either two spaces or three. Back
[7] "Normal mode:" in the eighties, this would have been called "word wrap." At the time, not only was there no succinct name for the feature, but the concept itself was unfamiliar enough need a precise explanation. As I write this in 1997, word wrap is so taken for granted in GUI text entry that there is no longer any need to have a name for it, and the term is falling into disuse. Back
[8] "Carriage return:" both returned the carriage and advanced the line on the typewriter mechanisms used on the PDP-1. There was no distinct "line feed" operation to be concerned with. Back
[9] "Concise code:" the character set used internally on the PDP-1,
a six-bit code formed by truncating the full "FIO-DEC" codes,
which included a parity bit. A portion of the table is reproduced here; notice that every code has both a "lower" and "upper" character; notice too the upper-case mappings of the numerals.
Back
[10] "Test word:" bank of eighteen toggle switches on the PDP-1 console, often playing the same role that a command-line argument would play today. There was no provision for varying margins within a document. Back
[11] Letters preceded by a overbar here, e.g. ¯q, appear in the original with an overbar above them. A nonspacing (dead key) overbar was part of the PDP-1 character set and frequently used as a syntactic convention to identify commands.
On lines containing these characters I have chosen to transcribe the spaces inserted for justification precisely as they appear in the original. I have not succeeded in finding a good way in HTML to display an overbar above a character, so lines containing these characters are now longer than the others. Back
[12] Note that the terms used are simply "input" and "output," not "input stream," "input file," "input text," etc. Back
[13] The period is outside the quotation marks. As The New Hacker's Dictionary, 1991, comments, "Hackers tend to use quotes as balanced delimiters like parentheses... This is incorrect according to standard American usage (which would put the ... final period inside the string quotes); however, it is counter-intuitive to hackers to mutilate literal strings with characters that don't belong to them." Back
[14] "Sense Switch:" a bank of six toggle switches on the PDP-1 console, often playing the same role that a command-line switch would play today. At the time, sense switches were common on computers, even large IBM computers. Back
[15] Since there was no text editor, "input from typewriter" was not much use except for testing, demonstrations, or tutorials. Back
[16] Irregular vertical spacing here is accurately transcribed from original. Back
[17] It's typical of the computer documentation style of the time that this is described verbally, with no picture of the screen. When hyphenating the word "justification," the display would initially show
J+U+S+T+I+F+I+C+A+T+I+O+N
The user would point the pen at hyphenation points until the display showed
J+U+S=T+I+F+I=C+A=T+I+O+N
[18] "Light pen:" a pointing device. It could not sense position, like a mouse. It merely signaled the presence of a point of light directly under it. Somewhat complicated strategies were needed to acquire and track the pen.
PDP-1 Type 30 Precision CRT Display, with light pen
Back
[19] The word "all" is underscored in the original. Back
[20] The "dictionary" was a temporary dictionary, kept in core (RAM) only for the duration of the session. This is not explained because it was taken for granted. There was no permanent online storage for user files. Back
[21] "Console version:" near the console was a device like a set of very small cubbyholes, designed to store fanfolded paper tapes. Programs for general use were stored in these cubbyholes and were referred to as the "console copies." There were about forty or fifty of them, including Expensive Typewriter, TECO, TJ-1, the MACRO and MIDAS assemblers, machine diagnostics, and SPACEWAR. Back
[22] AC, IO -- the two main active registers of the PDP-1, whose contents were displayed in a set of indicator lights on the front panel. Back
[23] -0 -- the PDP-1 was a one's complement machine. -0 was distinct from +0 and would have displayed as all lights on. Back
[24] The slight misalignment in the last column -- i.e. the "d" in "don't save" aligns with the "l" in "likewise," rather than the left parenthesis -- is an accurate copy of the original. Back
Additional key phrases: computer history; computer folklore; computer nostalgia; history of computing; DEC; Digital Equipment Corporation; TMRC.
Date created: 1/25/97 Last modified: 1/25/97 Copyright © 1997, Daniel P. B. Smith; All Rights Reserved Maintained by: Daniel P. B. Smith dpbsmith@world.std.com