Text Executive Programming Language

In 1979, Honeywell Information Systems announced a new programming language for their time-sharing service named TEX, an acronym for the Text Executive processor. TEX was a first generation scripting language, developed around the time of AWK and used by Honeywell initially as an in-house system test automation tool.

TEX extended the Honeywell Time-Sharing service (TSS) line editor with programmable capabilities which allowed the user greater latitude in developing ease-of-use editing extensions as well as write scripts to automate many other time-sharing tasks formerly done by more complex TSS FORTRAN programs.

Overview

TEX was a subsystem of Honeywell TSS. Users would enter the TSS command 'tex' to change to a TEX session mode of operation. TEX expressions could be entered directly on the command line or run from script file via the TEX command CALL <filename>.

TEX programs are a collection of TSS line editing commands, TSS session commands and TEX statements. TEX variables could be inserted into TSS commands and TSS line editor commands via the TEX variable substitution feature. TEX programs were primarily designed to extend the line editor system. Consequently, TEX had no concept of file input/output relying instead on applying line edit commands to the working file and saving as needed.

The key developers of TEX at Honeywell were Eric Clamons and Richard Keys with Robert Bemer, famous as the father of ASCII and grandfather of COBOL, acting in an advisory capacity.[1]

TEX should not be confused with TeX a typesetting markup language invented by Donald Knuth.

The American Mathematical Society has also claimed a trademark for TeX, which was rejected, because at the time this was tried (early 1980s), “TEX” (all caps) was registered by Honeywell for the “Text EXecutive” text processing system.[2]

Variables

All variables were stored as strings and converted to integer numeric values when required. Floating point variables, arrays or other datatypes common in current scripting languages did not exist in a TEX environment.

All variables were stored in a single global variable pool which users had to manage in order to avoid variable naming conflicts. There were no variable scoping capabilities in TEX. Variable names were limited to 40 characters.

TEX provided several internal read-only registers called star functions or star variables which changed state when certain TEX string parsing operations were executed. Star functions provided a means to get the current date and time, resultant strings from a split or scan string parsing operations, TEX internal call level and TSS session information.

The maximum length of a string value was 240 ASCII characters. This includes intermediate results when evaluating a TEX expression. Numeric string values are limited to 62 digits in the string including the (-) for negative numbers. Numeric values are also normalized where leading zeros are stripped from the string representation.

Some examples of variable usage: 

   _ we can use quotes or other characters as delimiters as long as the string doesn't contain them
   a="hello"

   _ here we use the / character as a delimiter (a common practice especially if the string has a " char)
   b=/world/
   _ here we are concatenating strings together via the comma concatenation operator
   c=a,/ /,b
   _ the out statement will print  "hello world" to the terminal without the quotes
   out:c
   _ here we use a TEX variable in a line editing command to find a line starting with "hello world"
   hello="hello world"
   f:hello
   _ here we are replacing the "hello" string with the "hello world" string
   rs:a:c

Operators

TEX has three types of operators:

When constructing a TEX expression, all spaces must be compressed out except for string literals. In general,spaces delimit TEX statements. 

   _ in the "d=" statement there are no spaces between the commas or the variables

   a="hello"   b=" "   c="world"   d=a,b,c   out:d
   _ the space separates the 'if' from the expression and the expression from the next TEX command to conditionally execute

   if a:eqs:"hello" out:a

Arithmetic

TEX supports only basic integer arithmetic operations:

with up to 16 levels of parentheses.

Some examples are: 

   a=1

   b=-2

   c=3*(a-b)/(2*2+(4+1))

Boolean operators

TEX boolean operators come in two flavors for:

They were most often used within the context of an IF control statement.

A list of available numeric boolean operators in TEX are:

A list of available string boolean operators are:

String boolean operators are affected by the TEX CASE mode. Under CASE mode, strings such as 'ABC' and 'abc' were considered equal (TEX converted 'ABC' to 'abc' prior to the comparison). Under NOCASE mode, the 'abc' string would be considered greater than the 'ABC' string based on the ASCII code point value for 'a' being a larger value than the 'A' ASCII code point value.

The boolean NOT operator was represented by the circumflex character (^).

Some examples of boolean operators in action: 

   if name:eqs:"luke"   out:"May the force be with you!"

   if ^age:gtn:500  out:"Heh, you can't be Yoda!"

TEX did not provide and or or connecters to make more complex boolean expressions. Instead, programmers had to use nested if statements for and connections and a block of if...do something statements to handle or connections: 

   _ an example of an and construct
   if a:eqs:'a'   if b:eqs:'b'  goto !its_true
   goto !its_false
   _ an example of an 'or construct
   if a:eqs:'a'   goto !its_true
   if b:eqs:'b'   goto !its_true
   if c:eqs:'c'   goto !its_true
   goto !its_false
   !its_true out:"Its true!" goto !next_block
   !its_false out:"Its false!" goto !next_block

   !next_block
   ...do something...

String operators

String concatenation in TEX was provided by the comma operator: 

   a="hello"," "," world"

TEX provided several string splitting operators:

Some string splitting examples: 

   a="hello world"

   b=a']5

   c=a]'5

   out:"It's a strange new ",c," but ",b," anyways!"

TEX provided several string scanning/parsing operators:

Some string scanning/parsing examples: 

   a="hello world"

   b=a'>" "

   out:b

Labels

All TEX statement labels were prefixed with a (!). Statement labels were in general ignored unless referenced by a goto or call statement. One notable feature of TEX was the ability to call or goto labels in other files. Coupled with the TEX SUBS mode meant that TEX could create new scripts via line editing, save and then call or goto labels in these scripts dynamically.

The mypgm file:

   !hello
   out:"hello world"
   return

   !hello2
   out:"hello world again"
   exit

   (end-of-file marker)

Calling by label example: 

   call /mycat/mypgm!hello

In the above example, TEX would process the /mycat/mypgm file searching for the !hello label(*). TEX would continue processing the file until a return statement or exit statement was executed or end of file was reached.

Goto by label example: 

   goto /mycat/mypgm!hello2

In the next example, TEX would process the /mycat/mypgm file searching for the !hello2 label(*). TEX would continue processing until an exit statement or end of file was reached. An error would be thrown if a return statement was executed and there were no CALLs active.

(*) TEX did not check for duplicate labels in the same file, consequently execution was unpredictable if present.

Substitutions

TEX provides the SUBS and NOSUBS commands to activate or deactivate variable substitution for subsequent TEX statements or TSS commands.

   xx=/out:"Hello World"/

   subs ?

   ?xx?

   nosubs

   ?xx?

In the above example, the xx variable contains a TEX output statement as its value. The subs command specifies that (?) is the substitution character for all future statements of the program. Upon processing the first ?xx? line, TEX will substitute in the out:"Hello World" command for ?xx? and then execute the resultant statement. The nosubs command turns off substitutions for subsequent statements and so TEX issues an error when it tries to execute the second ?xx? line.

Indirections

In addition to variable substitution, TEX supported variable indirection. Variables prefixed with the underscore character (_) were considered to contain a variable name as their contents and so TEX would use indirection to get the value. TEX limited indirection to 64 levels to avoid possible looping.

As an example:

    a="b"
    b="c"
    c="hello world"
 
    _ here the out would print "hello world" to the terminal, 
    _   since '''__a == _b == c''' and so the command became '''out:c'''.
    out:__a

Input/output

Honeywell Timesharing sessions had a concept of the working file. To edit an existing file, you would first make it the working file via the old command. To create a new file, you would first create it via the new command. Once changes were complete, you would either save (for new files) or resave the working file. Basically only one file could be open for editing at a time.

TEX programs were primarily designed to extend the line editor system. Consequently, TEX had no concept of file input/output relying instead on making changes to the working file via line edit commands and saving as needed.

However, TEX did provide terminal-oriented input/output commands:

A simple example using in and out: 

   in:"What is your name?"

   out:"Hi ",*in

Star variables and functions

TEX provided star variables as a means to access results or side-effects of TEX system functions or to represent ASCII terminal codes.

A list of star variables follows:

Terminal codes

Terminal codes were mapped into star functions for easy reference in TEX programs.

Commands

TEX was built on top of the TSS line editor, as such line editor commands could be used within a TEX program. TEX programs may have:

Edit commands

The general command format was: 

   verb:<search_expression>;<repeat_count>;<occurrence_count>:<replacement_string>

The <search_expression> could contain a range as in F:/hello/,/world/ to find all lines that start with the string "hello" and contain the string "world" too.

TEX provided standard line-based file editing commands:

Each command could be modified with a numeric repeat value or with an asterisk (*):

Commands can be further modified with a line matching string or expression:

For string mode, an S was added. Whenever /xxx/ was found within the line then the edit was applied:

Lastly, the commands can be further modified with V to turn on verify mode and with O to specify nth occurrence string mode:

There are a few other lesser used editing commands:

In all edit command formats, the /xxx/ or /yyy/ or 999 could be replaced with a TEX variable. In addition, the 999 value could be replaced with an asterisk (*) to denote all occurrences.

TEX commands

TEX did not provide commands for numeric or conditional looping or switch cases as is common in modern scripting languages. These had to be constructed using if, labels and goto commands. As an example, to eliminate duplicate lines from a file, one would use: 

   !ELIM_DUPS a=*cl f;1
   _
   !NEXT_LINE if *eof out:"task complete" return

   b=*cl if a:eqs:b d goto !NEXT_LINE

   a=b f;1 goto !NEXT_LINE

TEX commands:

TEX modes

TEX modes defined how other TEX commands would operate. The *svmd variable contained the current state of all TEX modes in the form of TEX commands to restore the modes. Each mode had an inverse command to turn the mode off which could be done at any time.

TSS commands

While beyond the scope of this article, the most commonly used TSS commands were:

Example code

This code was excerpted from a TEX based Adventure game written by a team of Explorer Scouts from GE Post 635, Schenectady New York circa 1980. The Adventure game was the first of several popular online text-based adventure games available on the GE Timesharing service. The scouts decided to create their own adventure game using TEX. The original Adventure game used two word commands to navigate Colossal Cave. The parser shown below handled simple two word commands like go west or move right and converted them into x,y deltas for positioning and directional orientation in the game.

Parsing the Adventure two word commands: 

   _ ...main body of program skipped here for brevity
   _    where a call !init and repeated calls to !parser are done...
   
   !init 
   _ force a clear screen on the televideo terminal
   out:*esc,":"
   
   _ clear program variables
   rmdr=*null
   del=0
   dir="n"
   xlocn=1    ylocn=1
   return
   _ _______________________________________________________________
   _
   _
   _ The PARSER subroutine interprets your input commands and tries to 
   _ pre-process them prior to returning to your program.
   _
   _
   !parser
   qry=*cr,*lf,"-->" sntc=*null call !ask1
   ergo !unkn_cmd verb=ans vdel=0 goto !$ans$_cmd
   _
   !walk_cmd   del=2     call !move_to  return
   !run_cmd    del=4     call !move_to  return
   !fly_cmd    del=6     call !move_to  return
   !swim_cmd   del=2     call !move_to  return
   !look_cmd   msg="mlk" call !sense_to return
   !listen_cmd msg="mli" call !sense_to return
   !smell_cmd  msg="msm" call !sense_it return
   !touch_cmd  msg="mto" call !sense_it return
   !taste_cmd  msg="mta" call !sense_it return
   !cast_cmd             call !cast_it  return
   !unkn_cmd   return

   !move_to call !ask3 if ans:eqs:*null goto !to_$dir$
   ercall !to_same call !to_$ans$
   _
   !to_locn xlocn=xlocn+xdel ylocn=ylocn+ydel return
   _
   !to_f
   !to_forward
   !to_ahead
   !to_same goto !to_$dir$
   _
   !to_b
   !to_backward goto !inv_$dir$
   _
   !to_r
   !to_right goto !rt_$dir$
   _
   !to_l
   !to_left goto !lt_$dir$
   _
   !inv_south
   !rt_northwest
   !lt_northeast
   !to_n
   !to_north dir="n" xdel=0 ydel=del return
   _
   !inv_west
   !rt_northeast
   !lt_southeast
   !to_e
   !to_east dir="e" xdel=del ydel=0 return
   _
   !inv_north
   !rt_southeast
   !lt_southwest
   !to_s
   !to_south dir="s" xdel=0 ydel=-del return
   _
   !inv_east
   !rt_southwest
   !lt_northwest
   !to_w
   !to_west dir="w" xdel=-del ydel=0 return
   _
   !to_very vdel=vdel+1 goto !to_same
   !to_fast del=del+vdel vdel=0 goto !to_same
   !to_slow del=del-vdel vdel=0 goto !to_same

   !sense_to call !ask3
   ercall !to_same call !to_$ans$ msg=msg,dir call !msg return
   _
   _
   _ _______________________________________________________________
   _
   !sense_it call !ask3
   !sense_it_1 if ans:eqs:*null in:verb," what ???" ans=*in goto !sense_it_1
   msg=msg,ans call !msg return
   _
   _
   _ _______________________________________________________________
   _
   !msg i=1
   !msg_1 ergo !msg_end out:$(msg,i)$ i=i+1 clear $(msg,i)$ goto !msg_1
   !msg_end return
   _
   _ The ASK subroutines get yout terminal input and break it up depending
   _ on the spaces.
   _
   !ask1 if rmdr:eqs:*null in:qry rmdr=*in sntc=*null
   !ask2 if sntc:eqs:*null scan:rmdr:"." sntc=*l rmdr=*r]'1
   !ask3 scan:sntc:" " ans=*l sntc=*r return

Rolling dice: 

   _
   _
   _ _______________________________________________________________
   _
   _ The DICE subroutine rolls the dice for you and returns the answer
   _ in the variable called DICE.
   _
   _ Input to the DICE subroutine is via the DICE variable as shown below :
   _
   _     1d6 - roll the 6-sided die once
   _     3d8 - roll the 8-sided die 3 times
   _     d%  - roll the 100-sided die once (percentage roll)
   _
   !dice if dice:eqs:"d%" dice="1d100"
   scan:dice:"d" i=*l j=*r dice=0
   
   !dice_1 
   k=*random if j:gt:9 k=k,*random
   k=k/j dice=dice+*rmdr+1
   i=i-1 if i:gt:0 goto !dice_1
   
   clear i clear j clear k 
   return

Televideo screen codes: 

   _ 
   _
   _ The following routines allow you to easily draw pictures on the
   _ the Televideo 950 terminal.
   _
   _      xyplot—positions the cursor
   _ 
   _      gr—turns graphics mode on
   _
   _      nogr—turns graphics mode off
   _
   _      clear—clears the screen
   _
   _      load—used by xyplot to load the xytbl
   _
   !xyplot
   ercall !load xytbl=xytbl
   cx=(xytbl]'(x-1))']1
   cy=(xytbl]'(y-1))']1
   out:*ESC,"=",cy,cx,z
   return
   _
   _
   !load
   xytbl=" !",/"/,"#$%&'()*+,-./"
   xytbl=xytbl,"0123456789:;<=>?",*AT,"ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_"
   xytbl=xytbl,"`abcdefghijklmnopqrstuvwxyz{|}~",*DEL
   return
   _
   _
   !gr nosubs
   out:*ESC,"$" subs $
   $*SVMD$ return
   !nogr out:*ESC,"%" return
   !clear out:*ESC,":" return

Notable features

The most notable feature in TEX was its SUBS mode allowing variable values to crossover and become executable code. It allowed a programmer to create new variables on the fly to be used in later TEX expressions in a LISP-like fashion. TEX also allowed programmers to create scripts on the fly via line editing, saving the content to file later to be executed as part of the current program using interfile call and goto statements. However, in most cases, these features were used to provide simple dynamic goto statements in code as seen in the Adventure game parser example. What other kinds of Artificial Intelligence constructs could be developed were never fully explored.

An example of creating variables on the fly and then using them to do an interfile goto. 

   _ incorporate x,y,z into the global variable pool
   cmd="x=1 y=2 z=3"
   subs ?
   ?cmd?
   _ next we modify mycat/mypgm_1_2 to say "hello world" we are writing some code to execute later in our script
   old mycat/mypgm_1_2
   r:*cl:/!label_3 out:'Hello World'/
   resave mycat/mypgm_1_2
   _ lastly we subs in x,y,z and then evaluate the goto mypgm_1_2!label_3 which does an interfile goto
   goto mycat/mypgm_?x?_?y?!label_?z?

The TEX program above illustrates dynamic script creation and then execution via substitution, file editing and interfile gotos. In effect, programs writing programs were possible although seldom done. In the above example, the mycat/mypgm_1_2 file would be executed at label_3 printing out "hello world".

References

  • TEX User Guide (DF72) - Honeywell Information Systems, Copyright 1979
  • TEX Quick Reference - Honeywell Information Systems, Copyright 1979
  • Software Catalog (AW15 Rev05), Honeywell Information Systems, Copyright 1979, Section 4 - Series 600/6000, Series 60/Level 66, pg 4-42 TEX Executive Processor
  • R.W.Bemer, "Introduction to the TEX language - Part I", Interface Age Magazine, volume 3, No. 8, 144-147, 1978 August
  • R.W.Bemer, "Introduction to the TEX language - Part II", Interface Age Magazine, volume3, No. 9, 124-127, 1978 September
  • R.W.Bemer, "Introduction to the TEX language - Part III", Interface Age Magazine, volume 3, No. 10, 126-131, 1978 October
  • R.W.Bemer, "TEX-based screen editor", Proc. HLSUA Forum XXXI, 158-160, 1980 Oct 12-15 World's first half-duplex full screen editor.

Notes

  1. ↑ Introduction to TEX, p.144 Interface Age - Aug 1978
  2. ↑
    • Donald E. Knuth. The TeXbook (Computers and Typesetting, Volume A). Reading, Massachusetts: Addison-Wesley, 1984. ISBN 0-201-13448-9.