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+% This program by D. E. Knuth is not copyrighted and can be used freely.
+% Version 0 was implemented in January 1982.
+% In February 1982 a new restriction on ligature steps was added.
+% In June 1982 the routines were divided into smaller pieces for IBM people,
+% and the result was designated "Version 1" in September 1982.
+% Slight changes were made in October, 1982, for version 0.6 of TeX.
+% Version 2 (July 1983) was released with TeX version 0.999.
+% Version 2.1 (September 1983) changed TEXINFO to FONTDIMEN.
+% Version 2.2 (February 1984) simplified decimal fraction output.
+% Version 2.3 (May 1984) fixed a bug when lh=17.
+% Version 2.4 (July 1984) fixed a bug involving unused ligature code.
+% Version 2.5 (September 1985) updated the standard codingscheme names.
+% Version 3 (October 1989) introduced new ligature capabilities.
+% Version 3.1 (November 1989) renamed z[] to lig_z[] for better portability.
+% Version 3.2 (February 2008) added a newline after a warning message.
+% Version 3.3 (January 2014) added a space to an error message (Breitenlohner),
+%  and tests nl>lig_size not 4*lig_size (C. M. Connelly, Melissa O'Neill).
+
+% Here is TeX material that gets inserted after \input webmac
+\def\hang{\hangindent 3em\indent\ignorespaces}
+\font\ninerm=cmr9
+\let\mc=\ninerm % medium caps for names like SAIL
+\def\PASCAL{Pascal}
+
+\def\(#1){} % this is used to make section names sort themselves better
+\def\9#1{} % this is used for sort keys in the index
+
+\def\title{TF\lowercase{to}PL}
+\def\contentspagenumber{201}
+\def\topofcontents{\null
+  \titlefalse % include headline on the contents page
+  \def\rheader{\mainfont\hfil \contentspagenumber}
+  \vfill
+  \centerline{\titlefont The {\ttitlefont TFtoPL} processor}
+  \vskip 15pt
+  \centerline{(Version 3.3, January 2014)}
+  \vfill}
+\def\botofcontents{\vfill
+  \centerline{\hsize 5in\baselineskip9pt
+    \vbox{\ninerm\noindent
+    The preparation of this report
+    was supported in part by the National Science
+    Foundation under grants IST-8201926 and MCS-8300984,
+    and by the System Development Foundation. `\TeX' is a
+    trademark of the American Mathematical Society.}}}
+\pageno=\contentspagenumber \advance\pageno by 1
+
+@* Introduction.
+The \.{TFtoPL} utility program converts \TeX\ font metric (``\.{TFM}'')
+files into equivalent property-list (``\.{PL}'') files. It also
+makes a thorough check of the given \.{TFM} file, using essentially the
+same algorithm as \TeX. Thus if \TeX\ complains that a \.{TFM}
+file is ``bad,'' this program will pinpoint the source or sources of
+badness. A \.{PL} file output by this program can be edited with
+a normal text editor, and the result can be converted back to \.{TFM}
+format using the companion program \.{PLtoTF}.
+
+The first \.{TFtoPL} program was designed by Leo Guibas in the summer of
+1978. Contributions by Frank Liang, Doug Wyatt, and Lyle Ramshaw
+also had a significant effect on the evolution of the present code.
+
+Extensions for an enhanced ligature mechanism were added by the author in 1989.
+
+The |banner| string defined here should be changed whenever \.{TFtoPL}
+gets modified.
+
+@d banner=='This is TFtoPL, Version 3.3' {printed when the program starts}
+
+@ This program is written entirely in standard \PASCAL, except that
+it occasionally has lower case letters in strings that are output.
+Such letters can be converted to upper case if necessary. The input is read
+from |tfm_file|, and the output is written on |pl_file|; error messages and
+other remarks are written on the |output| file, which the user may
+choose to assign to the terminal if the system permits it.
+@^system dependencies@>
+
+The term |print| is used instead of |write| when this program writes on
+the |output| file, so that all such output can be easily deflected.
+
+@d print(#)==write(#)
+@d print_ln(#)==write_ln(#)
+
+@p program TFtoPL(@!tfm_file,@!pl_file,@!output);
+label @<Labels in the outer block@>@/
+const @<Constants in the outer block@>@/
+type @<Types in the outer block@>@/
+var @<Globals in the outer block@>@/
+procedure initialize; {this procedure gets things started properly}
+  begin print_ln(banner);@/
+  @<Set initial values@>@/
+  end;
+
+@ If the program has to stop prematurely, it goes to the
+`|final_end|'.
+
+@d final_end=9999 {label for the end of it all}
+
+@<Labels...@>=final_end;
+
+@ The following parameters can be changed at compile time to extend or
+reduce \.{TFtoPL}'s capacity.
+
+@<Constants...@>=
+@!tfm_size=30000; {maximum length of |tfm| data, in bytes}
+@!lig_size=5000; {maximum length of |lig_kern| program, in words}
+@!hash_size=5003; {preferably a prime number, a bit larger than the number
+  of character pairs in lig/kern steps}
+
+@ Here are some macros for common programming idioms.
+
+@d incr(#) == #:=#+1 {increase a variable by unity}
+@d decr(#) == #:=#-1 {decrease a variable by unity}
+@d do_nothing == {empty statement}
+
+@* Font metric data.
+The idea behind \.{TFM} files is that typesetting routines like \TeX\
+need a compact way to store the relevant information about several
+dozen fonts, and computer centers need a compact way to store the
+relevant information about several hundred fonts. \.{TFM} files are
+compact, and most of the information they contain is highly relevant,
+so they provide a solution to the problem.
+
+The information in a \.{TFM} file appears in a sequence of 8-bit bytes.
+Since the number of bytes is always a multiple of 4, we could
+also regard the file as a sequence of 32-bit words; but \TeX\ uses the
+byte interpretation, and so does \.{TFtoPL}. Note that the bytes
+are considered to be unsigned numbers.
+
+@<Glob...@>=
+@!tfm_file:packed file of 0..255;
+
+@ On some systems you may have to do something special to read a
+packed file of bytes. For example, the following code didn't work
+when it was first tried at Stanford, because packed files have to be
+opened with a special switch setting on the \PASCAL\ that was used.
+@^system dependencies@>
+
+@<Set init...@>=
+reset(tfm_file);
+
+@ The first 24 bytes (6 words) of a \.{TFM} file contain twelve 16-bit
+integers that give the lengths of the various subsequent portions
+of the file. These twelve integers are, in order:
+$$\vbox{\halign{\hfil#&$\null=\null$#\hfil\cr
+|@!lf|&length of the entire file, in words;\cr
+|@!lh|&length of the header data, in words;\cr
+|@!bc|&smallest character code in the font;\cr
+|@!ec|&largest character code in the font;\cr
+|@!nw|&number of words in the width table;\cr
+|@!nh|&number of words in the height table;\cr
+|@!nd|&number of words in the depth table;\cr
+|@!ni|&number of words in the italic correction table;\cr
+|@!nl|&number of words in the lig/kern table;\cr
+|@!nk|&number of words in the kern table;\cr
+|@!ne|&number of words in the extensible character table;\cr
+|@!np|&number of font parameter words.\cr}}$$
+They are all nonnegative and less than $2^{15}$. We must have |bc-1<=ec<=255|,
+|ne<=256|, and
+$$\hbox{|lf=6+lh+(ec-bc+1)+nw+nh+nd+ni+nl+nk+ne+np|.}$$
+Note that a font may contain as many as 256 characters (if |bc=0| and |ec=255|),
+and as few as 0 characters (if |bc=ec+1|).
+
+Incidentally, when two or more 8-bit bytes are combined to form an integer of
+16 or more bits, the most significant bytes appear first in the file.
+This is called BigEndian order.
+
+@<Glob...@>=
+@!lf,@!lh,@!bc,@!ec,@!nw,@!nh,@!nd,@!ni,@!nl,@!nk,@!ne,@!np:0..@'77777;
+  {subfile sizes}
+
+@ The rest of the \.{TFM} file may be regarded as a sequence of ten data
+arrays having the informal specification
+$$\def\arr$[#1]#2${\&{array} $[#1]$ \&{of} #2}
+\vbox{\halign{\hfil\\{#}&$\,:\,$\arr#\hfil\cr
+header&|[0..lh-1]stuff|\cr
+char\_info&|[bc..ec]char_info_word|\cr
+width&|[0..nw-1]fix_word|\cr
+height&|[0..nh-1]fix_word|\cr
+depth&|[0..nd-1]fix_word|\cr
+italic&|[0..ni-1]fix_word|\cr
+lig\_kern&|[0..nl-1]lig_kern_command|\cr
+kern&|[0..nk-1]fix_word|\cr
+exten&|[0..ne-1]extensible_recipe|\cr
+param&|[1..np]fix_word|\cr}}$$
+The most important data type used here is a |@!fix_word|, which is
+a 32-bit representation of a binary fraction. A |fix_word| is a signed
+quantity, with the two's complement of the entire word used to represent
+negation. Of the 32 bits in a |fix_word|, exactly 12 are to the left of the
+binary point; thus, the largest |fix_word| value is $2048-2^{-20}$, and
+the smallest is $-2048$. We will see below, however, that all but one of
+the |fix_word| values will lie between $-16$ and $+16$.
+
+@ The first data array is a block of header information, which contains
+general facts about the font. The header must contain at least two words,
+and for \.{TFM} files to be used with Xerox printing software it must
+contain at least 18 words, allocated as described below. When different
+kinds of devices need to be interfaced, it may be necessary to add further
+words to the header block.
+
+\yskip\hang|header[0]| is a 32-bit check sum that \TeX\ will copy into the
+\.{DVI} output file whenever it uses the font.  Later on when the \.{DVI}
+file is printed, possibly on another computer, the actual font that gets
+used is supposed to have a check sum that agrees with the one in the
+\.{TFM} file used by \TeX. In this way, users will be warned about
+potential incompatibilities. (However, if the check sum is zero in either
+the font file or the \.{TFM} file, no check is made.)  The actual relation
+between this check sum and the rest of the \.{TFM} file is not important;
+the check sum is simply an identification number with the property that
+incompatible fonts almost always have distinct check sums.
+@^check sum@>
+
+\yskip\hang|header[1]| is a |fix_word| containing the design size of the
+font, in units of \TeX\ points (7227 \TeX\ points = 254 cm).  This number
+must be at least 1.0; it is fairly arbitrary, but usually the design size
+is 10.0 for a ``10 point'' font, i.e., a font that was designed to look
+best at a 10-point size, whatever that really means. When a \TeX\ user
+asks for a font `\.{at} $\delta$ \.{pt}', the effect is to override the
+design size and replace it by $\delta$, and to multiply the $x$ and~$y$
+coordinates of the points in the font image by a factor of $\delta$
+divided by the design size.  {\sl All other dimensions in the\/\ \.{TFM}
+file are |fix_word|\kern-1pt\ numbers in design-size units.} Thus, for example,
+the value of |param[6]|, one \.{em} or \.{\\quad}, is often the |fix_word|
+value $2^{20}=1.0$, since many fonts have a design size equal to one em.
+The other dimensions must be less than 16 design-size units in absolute
+value; thus, |header[1]| and |param[1]| are the only |fix_word| entries in
+the whole \.{TFM} file whose first byte might be something besides 0 or
+255.  @^design size@>
+
+\yskip\hang|header[2..11]|, if present, contains 40 bytes that identify
+the character coding scheme. The first byte, which must be between 0 and
+39, is the number of subsequent ASCII bytes actually relevant in this
+string, which is intended to specify what character-code-to-symbol
+convention is present in the font.  Examples are \.{ASCII} for standard
+ASCII, \.{TeX text} for fonts like \.{cmr10} and \.{cmti9}, \.{TeX math
+extension} for \.{cmex10}, \.{XEROX text} for Xerox fonts, \.{GRAPHIC} for
+special-purpose non-alphabetic fonts, \.{UNSPECIFIED} for the default case
+when there is no information.  Parentheses should not appear in this name.
+(Such a string is said to be in {\mc BCPL} format.)
+@^coding scheme@>
+
+\yskip\hang|header[12..16]|, if present, contains 20 bytes that name the
+font family (e.g., \.{CMR} or \.{HELVETICA}), in {\mc BCPL} format.
+This field is also known as the ``font identifier.''
+@^family name@>
+@^font identifier@>
+
+\yskip\hang|header[17]|, if present, contains a first byte called the
+|seven_bit_safe_flag|, then two bytes that are ignored, and a fourth byte
+called the |face|. If the value of the fourth byte is less than 18, it has
+the following interpretation as a ``weight, slope, and expansion'':  Add 0
+or 2 or 4 (for medium or bold or light) to 0 or 1 (for roman or italic) to
+0 or 6 or 12 (for regular or condensed or extended).  For example, 13 is
+0+1+12, so it represents medium italic extended.  A three-letter code
+(e.g., \.{MIE}) can be used for such |face| data.
+
+\yskip\hang|header[18..@twhatever@>]| might also be present; the individual
+words are simply called |header[18]|, |header[19]|, etc., at the moment.
+
+@ Next comes the |char_info| array, which contains one |char_info_word|
+per character. Each |char_info_word| contains six fields packed into
+four bytes as follows.
+
+\yskip\hang first byte: |width_index| (8 bits)\par
+\hang second byte: |height_index| (4 bits) times 16, plus |depth_index|
+  (4~bits)\par
+\hang third byte: |italic_index| (6 bits) times 4, plus |tag|
+  (2~bits)\par
+\hang fourth byte: |remainder| (8 bits)\par
+\yskip\noindent
+The actual width of a character is |width[width_index]|, in design-size
+units; this is a device for compressing information, since many characters
+have the same width. Since it is quite common for many characters
+to have the same height, depth, or italic correction, the \.{TFM} format
+imposes a limit of 16 different heights, 16 different depths, and
+64 different italic corrections.
+
+Incidentally, the relation |width[0]=height[0]=depth[0]=italic[0]=0|
+should always hold, so that an index of zero implies a value of zero.
+The |width_index| should never be zero unless the character does
+not exist in the font, since a character is valid if and only if it lies
+between |bc| and |ec| and has a nonzero |width_index|.
+
+@ The |tag| field in a |char_info_word| has four values that explain how to
+interpret the |remainder| field.
+
+\yskip\hang|tag=0| (|no_tag|) means that |remainder| is unused.\par
+\hang|tag=1| (|lig_tag|) means that this character has a ligature/kerning
+program starting at |lig_kern[remainder]|.\par
+\hang|tag=2| (|list_tag|) means that this character is part of a chain of
+characters of ascending sizes, and not the largest in the chain.  The
+|remainder| field gives the character code of the next larger character.\par
+\hang|tag=3| (|ext_tag|) means that this character code represents an
+extensible character, i.e., a character that is built up of smaller pieces
+so that it can be made arbitrarily large. The pieces are specified in
+|exten[remainder]|.\par
+
+@d no_tag=0 {vanilla character}
+@d lig_tag=1 {character has a ligature/kerning program}
+@d list_tag=2 {character has a successor in a charlist}
+@d ext_tag=3 {character is extensible}
+
+@ The |lig_kern| array contains instructions in a simple programming language
+that explains what to do for special letter pairs. Each word is a
+|lig_kern_command| of four bytes.
+
+\yskip\hang first byte: |skip_byte|, indicates that this is the final program
+  step if the byte is 128 or more, otherwise the next step is obtained by
+  skipping this number of intervening steps.\par
+\hang second byte: |next_char|, ``if |next_char| follows the current character,
+  then perform the operation and stop, otherwise continue.''\par
+\hang third byte: |op_byte|, indicates a ligature step if less than~128,
+  a kern step otherwise.\par
+\hang fourth byte: |remainder|.\par
+\yskip\noindent
+In a kern step, an
+additional space equal to |kern[256*(op_byte-128)+remainder]| is inserted
+between the current character and |next_char|. This amount is
+often negative, so that the characters are brought closer together
+by kerning; but it might be positive.
+
+There are eight kinds of ligature steps, having |op_byte| codes $4a+2b+c$ where
+$0\le a\le b+c$ and $0\le b,c\le1$. The character whose code is
+|remainder| is inserted between the current character and |next_char|;
+then the current character is deleted if $b=0$, and |next_char| is
+deleted if $c=0$; then we pass over $a$~characters to reach the next
+current character (which may have a ligature/kerning program of its own).
+
+Notice that if $a=0$ and $b=1$, the current character is unchanged; if
+$a=b$ and $c=1$, the current character is changed but the next character is
+unchanged. \.{TFtoPL} will check to see that infinite loops are avoided.
+
+If the very first instruction of the |lig_kern| array has |skip_byte=255|,
+the |next_char| byte is the so-called right boundary character of this font;
+the value of |next_char| need not lie between |bc| and~|ec|.
+If the very last instruction of the |lig_kern| array has |skip_byte=255|,
+there is a special ligature/kerning program for a left boundary character,
+beginning at location |256*op_byte+remainder|.
+The interpretation is that \TeX\ puts implicit boundary characters
+before and after each consecutive string of characters from the same font.
+These implicit characters do not appear in the output, but they can affect
+ligatures and kerning.
+
+If the very first instruction of a character's |lig_kern| program has
+|skip_byte>128|, the program actually begins in location
+|256*op_byte+remainder|. This feature allows access to large |lig_kern|
+arrays, because the first instruction must otherwise
+appear in a location |<=255|.
+
+Any instruction with |skip_byte>128| in the |lig_kern| array must have
+|256*op_byte+remainder<nl|. If such an instruction is encountered during
+normal program execution, it denotes an unconditional halt; no ligature
+command is performed.
+
+@d stop_flag=128 {value indicating `\.{STOP}' in a lig/kern program}
+@d kern_flag=128 {op code for a kern step}
+
+@ Extensible characters are specified by an |extensible_recipe|,
+which consists of four bytes called |top|, |mid|,
+|bot|, and |rep| (in this order). These bytes are the character codes
+of individual pieces used to build up a large symbol.
+If |top|, |mid|, or |bot| are zero,
+they are not present in the built-up result. For example, an extensible
+vertical line is like an extensible bracket, except that the top and
+bottom pieces are missing.
+
+
+@ The final portion of a \.{TFM} file is the |param| array, which is another
+sequence of |fix_word| values.
+
+\yskip\hang|param[1]=@!slant| is the amount of italic slant, which is used
+to help position accents. For example, |slant=.25| means that when you go
+up one unit, you also go .25 units to the right. The |slant| is a pure
+number; it's the only |fix_word| other than the design size itself that is
+not scaled by the design size.
+
+\hang|param[2]=space| is the normal spacing between words in text.
+Note that character |" "| in the font need not have anything to do with
+blank spaces.
+
+\hang|param[3]=space_stretch| is the amount of glue stretching between words.
+
+\hang|param[4]=space_shrink| is the amount of glue shrinking between words.
+
+\hang|param[5]=x_height| is the height of letters for which accents don't
+have to be raised or lowered.
+
+\hang|param[6]=quad| is the size of one em in the font.
+
+\hang|param[7]=extra_space| is the amount added to |param[2]| at the
+ends of sentences.
+
+When the character coding scheme is \.{TeX math symbols}, the font is
+supposed to have 15 additional parameters called |num1|, |num2|, |num3|,
+|denom1|, |denom2|, |sup1|, |sup2|, |sup3|, |sub1|, |sub2|, |supdrop|,
+|subdrop|, |delim1|, |delim2|, and |axis_height|, respectively. When the
+character coding scheme is \.{TeX math extension}, the font is supposed to
+have six additional parameters called |default_rule_thickness| and
+|big_op_spacing1| through |big_op_spacing5|.
+
+@ So that is what \.{TFM} files hold. The next question is, ``What about
+\.{PL} files?'' A complete answer to that question appears in the
+documentation of the companion program, \.{PLtoTF}, so it will not
+be repeated here. Suffice it to say that a \.{PL} file is an ordinary
+\PASCAL\ text file, and that the output of \.{TFtoPL} uses only a
+subset of the possible constructions that might appear in a \.{PL} file.
+Furthermore, hardly anybody really wants to look at the formal
+definition of \.{PL} format, because it is almost self-explanatory when
+you see an example or two.
+
+@<Glob...@>=
+@!pl_file:text;
+
+@ @<Set init...@>=
+rewrite(pl_file);
+
+@* Unpacked representation.
+The first thing \.{TFtoPL} does is read the entire |tfm_file| into an array of
+bytes, |tfm[0..(4*lf-1)]|.
+
+@<Types...@>=
+@!byte=0..255; {unsigned eight-bit quantity}
+@!index=0..tfm_size; {address of a byte in |tfm|}
+
+@ @<Glob...@>=
+@!tfm:array [-1000..tfm_size] of byte; {the input data all goes here}
+ {the negative addresses avoid range checks for invalid characters}
+
+@ The input may, of course, be all screwed up and not a \.{TFM} file
+at all. So we begin cautiously.
+
+@d abort(#)==begin print_ln(#);
+  print_ln('Sorry, but I can''t go on; are you sure this is a TFM?');
+  goto final_end;
+  end
+
+@<Read the whole input file@>=
+read(tfm_file,tfm[0]);
+if tfm[0]>127 then abort('The first byte of the input file exceeds 127!');
+@.The first byte...@>
+if eof(tfm_file) then abort('The input file is only one byte long!');
+@.The input...one byte long@>
+read(tfm_file,tfm[1]); lf:=tfm[0]*@'400+tfm[1];
+if lf=0 then
+  abort('The file claims to have length zero, but that''s impossible!');
+@.The file claims...@>
+if 4*lf-1>tfm_size then abort('The file is bigger than I can handle!');
+@.The file is bigger...@>
+for tfm_ptr:=2 to 4*lf-1 do
+  begin if eof(tfm_file) then
+    abort('The file has fewer bytes than it claims!');
+@.The file has fewer bytes...@>
+  read(tfm_file,tfm[tfm_ptr]);
+  end;
+if not eof(tfm_file) then
+  begin print_ln('There''s some extra junk at the end of the TFM file,');
+@.There's some extra junk...@>
+  print_ln('but I''ll proceed as if it weren''t there.');
+  end
+
+@ After the file has been read successfully, we look at the subfile sizes
+to see if they check out.
+
+@d eval_two_bytes(#)==begin if tfm[tfm_ptr]>127 then
+    abort('One of the subfile sizes is negative!');
+@.One of the subfile sizes...@>
+  #:=tfm[tfm_ptr]*@'400+tfm[tfm_ptr+1];
+  tfm_ptr:=tfm_ptr+2;
+  end
+
+@<Set subfile sizes |lh|, |bc|, \dots, |np|@>=
+begin tfm_ptr:=2;@/
+eval_two_bytes(lh);
+eval_two_bytes(bc);
+eval_two_bytes(ec);
+eval_two_bytes(nw);
+eval_two_bytes(nh);
+eval_two_bytes(nd);
+eval_two_bytes(ni);
+eval_two_bytes(nl);
+eval_two_bytes(nk);
+eval_two_bytes(ne);
+eval_two_bytes(np);
+if lh<2 then abort('The header length is only ',lh:1,'!');
+@.The header length...@>
+if nl>lig_size then
+  abort('The lig/kern program is longer than I can handle!');
+@.The lig/kern program...@>
+if (bc>ec+1)or(ec>255) then abort('The character code range ',
+@.The character code range...@>
+  bc:1,'..',ec:1,' is illegal!');
+if (nw=0)or(nh=0)or(nd=0)or(ni=0) then
+  abort('Incomplete subfiles for character dimensions!');
+@.Incomplete subfiles...@>
+if ne>256 then abort('There are ',ne:1,' extensible recipes!');
+@.There are ... recipes@>
+if lf<>6+lh+(ec-bc+1)+nw+nh+nd+ni+nl+nk+ne+np then
+  abort('Subfile sizes don''t add up to the stated total!');
+@.Subfile sizes don't add up...@>
+end
+
+@ Once the input data successfully passes these basic checks,
+\.{TFtoPL} believes that it is a \.{TFM} file, and the conversion
+to \.{PL} format will take place. Access to the various subfiles
+is facilitated by computing the following base addresses. For example,
+the |char_info| for character |c| will start in location
+|4*(char_base+c)| of the |tfm| array.
+
+@<Globals...@>=
+@!char_base,@!width_base,@!height_base,@!depth_base,@!italic_base,
+@!lig_kern_base,@!kern_base,@!exten_base,@!param_base:integer;
+  {base addresses for the subfiles}
+
+@ @<Compute the base addresses@>=
+begin char_base:=6+lh-bc;
+width_base:=char_base+ec+1;
+height_base:=width_base+nw;
+depth_base:=height_base+nh;
+italic_base:=depth_base+nd;
+lig_kern_base:=italic_base+ni;
+kern_base:=lig_kern_base+nl;
+exten_base:=kern_base+nk;
+param_base:=exten_base+ne-1;
+end
+
+@ Of course we want to define macros that suppress the detail of how the
+font information is actually encoded. Each word will be referred to by
+the |tfm| index of its first byte. For example, if |c| is a character
+code between |bc| and |ec|, then |tfm[char_info(c)]| will be the
+first byte of its |char_info|, i.e., the |width_index|; furthermore
+|width(c)| will point to the |fix_word| for |c|'s width.
+
+@d check_sum=24
+@d design_size=check_sum+4
+@d scheme=design_size+4
+@d family=scheme+40
+@d random_word=family+20
+@d char_info(#)==4*(char_base+#)
+@d width_index(#)==tfm[char_info(#)]
+@d nonexistent(#)==((#<bc)or(#>ec)or(width_index(#)=0))
+@d height_index(#)==(tfm[char_info(#)+1] div 16)
+@d depth_index(#)==(tfm[char_info(#)+1] mod 16)
+@d italic_index(#)==(tfm[char_info(#)+2] div 4)
+@d tag(#)==(tfm[char_info(#)+2] mod 4)
+@d reset_tag(#)==tfm[char_info(#)+2]:=4*italic_index(#)+no_tag
+@d remainder(#)==tfm[char_info(#)+3]
+@d width(#)==4*(width_base+width_index(#))
+@d height(#)==4*(height_base+height_index(#))
+@d depth(#)==4*(depth_base+depth_index(#))
+@d italic(#)==4*(italic_base+italic_index(#))
+@d exten(#)==4*(exten_base+remainder(#))
+@d lig_step(#)==4*(lig_kern_base+(#))
+@d kern(#)==4*(kern_base+#) {here \#\ is an index, not a character}
+@d param(#)==4*(param_base+#) {likewise}
+
+@ One of the things we would like to do is take cognizance of fonts whose
+character coding scheme is \.{TeX math symbols} or \.{TeX math extension};
+we will set the |font_type| variable to one of the three choices
+|vanilla|, |mathsy|, or |mathex|.
+
+@d vanilla=0 {not a special scheme}
+@d mathsy=1 {\.{TeX math symbols} scheme}
+@d mathex=2 {\.{TeX math extension} scheme}
+
+@<Glob...@>=
+@!font_type:vanilla..mathex; {is this font special?}
+
+@* Basic output subroutines.
+Let us now define some procedures that will reduce the rest of \.{TFtoPL}'s
+work to a triviality.
+
+First of all, it is convenient to have an abbreviation for output to the
+\.{PL} file:
+
+@d out(#)==write(pl_file,#)
+
+@ In order to stick to standard \PASCAL, we use three strings called
+|ASCII_04|, |ASCII_10|, and |ASCII_14|, in terms of which we can do the
+appropriate conversion of ASCII codes. Three other little strings are
+used to produce |face| codes like \.{MIE}.
+
+@<Glob...@>=
+@!ASCII_04,@!ASCII_10,@!ASCII_14: packed array [1..32] of char;
+  {strings for output in the user's external character set}
+@!MBL_string,@!RI_string,@!RCE_string:packed array [1..3] of char;
+  {handy string constants for |face| codes}
+
+@ @<Set init...@>=
+ASCII_04:=' !"#$%&''()*+,-./0123456789:;<=>?';@/
+ASCII_10:='@@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_';@/
+ASCII_14:='`abcdefghijklmnopqrstuvwxyz{|}~ ';@/
+MBL_string:='MBL'; RI_string:='RI '; RCE_string:='RCE';
+
+@ The array |dig| will hold a sequence of digits to be output.
+
+@<Glob...@>=
+@!dig:array[0..11] of 0..9;
+
+@ Here, in fact, are two procedures that output |dig[j-1]|$\,\ldots\,$|dig[0]|,
+given $j>0$.
+
+@p procedure out_digs(j:integer); {outputs |j| digits}
+begin repeat decr(j); out(dig[j]:1);
+until j=0;
+end;
+@#
+procedure print_digs(j:integer); {prints |j| digits}
+begin repeat decr(j); print(dig[j]:1);
+until j=0;
+end;
+
+@ The |print_octal| procedure indicates how |print_digs| can be used.
+Since this procedure is used only to print character codes, it always
+produces three digits.
+
+@p procedure print_octal(c:byte); {prints octal value of |c|}
+var j:0..2; {index into |dig|}
+begin print(''''); {an apostrophe indicates the octal notation}
+for j:=0 to 2 do
+  begin dig[j]:=c mod 8; c:=c div 8;
+  end;
+print_digs(3);
+end;
+
+@ A \.{PL} file has nested parentheses, and we want to format the output
+so that its structure is clear. The |level| variable keeps track of the
+depth of nesting.
+
+@<Glob...@>=
+@!level:0..5;
+
+@ @<Set init...@>=
+level:=0;
+
+@ Three simple procedures suffice to produce the desired structure in the
+output.
+
+@p procedure out_ln; {finishes one line, indents the next}
+var l:0..5;
+begin write_ln(pl_file);
+for l:=1 to level do out('   ');
+end;
+@#
+procedure left; {outputs a left parenthesis}
+begin incr(level); out('(');
+end;
+@#
+procedure right; {outputs a right parenthesis and finishes a line}
+begin decr(level); out(')'); out_ln;
+end;
+
+@ The value associated with a property can be output in a variety of
+ways. For example, we might want to output a {\mc BCPL} string that
+begins in |tfm[k]|:
+
+@p procedure out_BCPL(@!k:index); {outputs a string, preceded by a blank space}
+var l:0..39; {the number of bytes remaining}
+begin out(' '); l:=tfm[k];
+while l>0 do
+  begin incr(k); decr(l);
+  case tfm[k] div @'40 of
+  1: out(ASCII_04[1+(tfm[k] mod @'40)]);
+  2: out(ASCII_10[1+(tfm[k] mod @'40)]);
+  3: out(ASCII_14[1+(tfm[k] mod @'40)]);
+  end;
+  end;
+end;
+
+@ The property value might also be a sequence of |l| bytes, beginning
+in |tfm[k]|, that we would like to output in octal notation.
+The following procedure assumes that |l<=4|, but larger values of |l|
+could be handled easily by enlarging the |dig| array and increasing
+the upper bounds on |b| and |j|.
+
+@p procedure out_octal(@!k,@!l:index); {outputs |l| bytes in octal}
+var a:0..@'1777; {accumulator for bits not yet output}
+@!b:0..32; {the number of significant bits in |a|}
+@!j:0..11; {the number of digits of output}
+begin out(' O '); {specify octal format}
+a:=0; b:=0; j:=0;
+while l>0 do @<Reduce \(1)|l| by one, preserving the invariants@>;
+while (a>0)or(j=0) do
+  begin dig[j]:=a mod 8; a:=a div 8; incr(j);
+  end;
+out_digs(j);
+end;
+
+@ @<Reduce \(1)|l|...@>=
+begin decr(l);
+if tfm[k+l]<>0 then
+  begin while b>2 do
+    begin dig[j]:=a mod 8; a:=a div 8; b:=b-3; incr(j);
+    end;
+  case b of
+  0: a:=tfm[k+l];
+  1:a:=a+2*tfm[k+l];
+  2:a:=a+4*tfm[k+l];
+  end;
+  end;
+b:=b+8;
+end
+
+@ The property value may be a character, which is output in octal
+unless it is a letter or a digit. This procedure is the only place
+where a lowercase letter will be output to the \.{PL} file.
+@^system dependencies@>
+
+@p procedure out_char(@!c:byte); {outputs a character}
+begin if font_type>vanilla then
+  begin tfm[0]:=c; out_octal(0,1)
+  end
+else if (c>="0")and(c<="9") then
+  out(' C ',c-"0":1)
+else if (c>="A")and(c<="Z") then
+  out(' C ',ASCII_10[c-"A"+2])
+else if (c>="a")and(c<="z") then
+  out(' C ',ASCII_14[c-"a"+2])
+else  begin tfm[0]:=c; out_octal(0,1);
+  end;
+end;
+
+@ The property value might be a ``face'' byte, which is output in the
+curious code mentioned earlier, provided that it is less than 18.
+
+@p procedure out_face(@!k:index); {outputs a |face|}
+var s:0..1; {the slope}
+@!b:0..8; {the weight and expansion}
+begin if tfm[k]>=18 then out_octal(k,1)
+else  begin out(' F ');  {specify face-code format}
+  s:=tfm[k] mod 2; b:=tfm[k] div 2;
+  out(MBL_string[1+(b mod 3)]);
+  out(RI_string[1+s]);
+  out(RCE_string[1+(b div 3)]);
+  end;
+end;
+
+@ And finally, the value might be a |fix_word|, which is output in
+decimal notation with just enough decimal places for \.{PLtoTF}
+to recover every bit of the given |fix_word|.
+
+All of the numbers involved in the intermediate calculations of
+this procedure will be nonnegative and less than $10\cdot2^{24}$.
+
+@p procedure out_fix(@!k:index); {outputs a |fix_word|}
+var a:0..@'7777; {accumulator for the integer part}
+@!f:integer; {accumulator for the fraction part}
+@!j:0..12; {index into |dig|}
+@!delta:integer; {amount if allowable inaccuracy}
+begin out(' R '); {specify real format}
+a:=(tfm[k]*16)+(tfm[k+1] div 16);
+f:=((tfm[k+1] mod 16)*@'400+tfm[k+2])*@'400+tfm[k+3];
+if a>@'3777 then @<Reduce \(2)negative to positive@>;
+@<Output the integer part, |a|, in decimal notation@>;
+@<Output the fraction part, $|f|/2^{20}$, in decimal notation@>;
+end;
+
+@ The following code outputs at least one digit even if |a=0|.
+
+@<Output the integer...@>=
+begin j:=0;
+repeat dig[j]:=a mod 10; a:=a div 10; incr(j);
+until a=0;
+out_digs(j);
+end
+
+@ And the following code outputs at least one digit to the right
+of the decimal point.
+
+@<Output the fraction...@>=
+begin out('.'); f:=10*f+5; delta:=10;
+repeat if delta>@'4000000 then f:=f+@'2000000-(delta div 2);
+out(f div @'4000000:1); f:=10*(f mod @'4000000); delta:=delta*10;
+until f<=delta;
+end;
+
+@ @<Reduce \(2)negative to positive@>=
+begin out('-'); a:=@'10000-a;
+if f>0 then
+  begin f:=@'4000000-f; decr(a);
+  end;
+end
+
+@* Doing it.
+\TeX\ checks the information of a \.{TFM} file for validity as the
+file is being read in, so that no further checks will be needed when
+typesetting is going on. And when it finds something wrong, it just
+calls the file ``bad,'' without identifying the nature of the problem,
+since \.{TFM} files are supposed to be good almost all of the time.
+
+Of course, a bad file shows up every now and again, and that's where
+\.{TFtoPL} comes in. This program wants to catch at least as many errors as
+\TeX\ does, and to give informative error messages besides.
+All of the errors are corrected, so that the \.{PL} output will
+be correct (unless, of course, the \.{TFM} file was so loused up
+that no attempt is being made to fathom it).
+
+@ Just before each character is processed, its code is printed in octal
+notation. Up to eight such codes appear on a line; so we have a variable
+to keep track of how many are currently there. We also keep track of
+whether or not any errors have had to be corrected.
+
+@<Glob...@>=
+@!chars_on_line:0..8; {the number of characters printed on the current line}
+@!perfect:boolean; {was the file free of errors?}
+
+@ @<Set init...@>=
+chars_on_line:=0;@/
+perfect:=true; {innocent until proved guilty}
+
+@ Error messages are given with the help of the |bad| and |range_error|
+and |bad_char| macros:
+
+@d bad(#)==begin perfect:=false; if chars_on_line>0 then print_ln(' ');
+  chars_on_line:=0; print_ln('Bad TFM file: ',#);
+  end
+@.Bad TFM file@>
+@d range_error(#)==begin perfect:=false; print_ln(' ');
+  print(#,' index for character ');
+  print_octal(c); print_ln(' is too large;');
+  print_ln('so I reset it to zero.');
+  end
+@d bad_char_tail(#)==print_octal(#); print_ln('.');
+  end
+@d bad_char(#)==begin perfect:=false; if chars_on_line>0 then print_ln(' ');
+  chars_on_line:=0; print('Bad TFM file: ',#,' nonexistent character ');
+  bad_char_tail
+@d correct_bad_char_tail(#)==print_octal(tfm[#]); print_ln('.'); tfm[#]:=bc;
+  end
+@d correct_bad_char(#)== begin perfect:=false;
+  if chars_on_line>0 then print_ln(' ');
+  chars_on_line:=0; print('Bad TFM file: ',#,' nonexistent character ');
+  correct_bad_char_tail
+
+@<Glob...@>=
+@!i:0..@'77777; {an index to words of a subfile}
+@!c:0..256; {a random character}
+@!d:0..3; {byte number in a word}
+@!k:index; {a random index}
+@!r:0..65535; {a random two-byte value}
+@!count:0..127; {for when we need to enumerate a small set}
+
+@ There are a lot of simple things to do, and they have to be done one
+at a time, so we might as well get down to business.  The first things
+that \.{TFtoPL} will put into the \.{PL} file appear in the header part.
+
+@<Do the header@>=
+begin font_type:=vanilla;
+if lh>=12 then
+  begin @<Set the true |font_type|@>;
+  if lh>=17 then
+    begin @<Output the family name@>;
+    if lh>=18 then @<Output the rest of the header@>;
+    end;
+  @<Output the character coding scheme@>;
+  end;
+@<Output the design size@>;
+@<Output the check sum@>;
+@<Output the |seven_bit_safe_flag|@>;
+end
+
+@ @<Output the check sum@>=
+left; out('CHECKSUM'); out_octal(check_sum,4);
+right
+
+@ Incorrect design sizes are changed to 10 points.
+
+@d bad_design(#)==begin bad('Design size ',#,'!');
+@.Design size wrong@>
+  print_ln('I''ve set it to 10 points.');
+  out(' D 10');
+  end
+
+@ @<Output the design size@>=
+left; out('DESIGNSIZE');
+if tfm[design_size]>127 then bad_design('negative')
+else if (tfm[design_size]=0)and(tfm[design_size+1]<16) then
+  bad_design('too small')
+else out_fix(design_size);
+right;
+out('(COMMENT DESIGNSIZE IS IN POINTS)'); out_ln;
+out('(COMMENT OTHER SIZES ARE MULTIPLES OF DESIGNSIZE)'); out_ln
+@.DESIGNSIZE IS IN POINTS@>
+
+@ Since we have to check two different {\mc BCPL} strings for validity,
+we might as well write a subroutine to make the check.
+
+@p procedure check_BCPL(@!k,@!l:index); {checks a string of length |<l|}
+var j:index; {runs through the string}
+@!c:byte; {character being checked}
+begin if tfm[k]>=l then
+  begin bad('String is too long; I''ve shortened it drastically.');
+@.String is too long...@>
+  tfm[k]:=1;
+  end;
+for j:=k+1 to k+tfm[k] do
+  begin c:=tfm[j];
+  if (c="(")or(c=")") then
+    begin bad('Parenthesis in string has been changed to slash.');
+@.Parenthesis...changed to slash@>
+    tfm[j]:="/";
+    end
+  else if (c<" ")or(c>"~") then
+    begin bad('Nonstandard ASCII code has been blotted out.');
+@.Nonstandard ASCII code...@>
+    tfm[j]:="?";
+    end
+  else if (c>="a")and(c<="z") then tfm[j]:=c+"A"-"a"; {upper-casify letters}
+  end;
+end;
+
+@ The |font_type| starts out |vanilla|; possibly we need to reset it.
+
+@<Set the true |font_type|@>=
+begin check_BCPL(scheme,40);
+if (tfm[scheme]>=11)and@|(tfm[scheme+1]="T")and@|
+  (tfm[scheme+2]="E")and@|(tfm[scheme+3]="X")and@|
+  (tfm[scheme+4]=" ")and@|(tfm[scheme+5]="M")and@|
+  (tfm[scheme+6]="A")and@|(tfm[scheme+7]="T")and@|
+  (tfm[scheme+8]="H")and@|(tfm[scheme+9]=" ") then
+  begin if (tfm[scheme+10]="S")and(tfm[scheme+11]="Y") then font_type:=mathsy
+  else if (tfm[scheme+10]="E")and(tfm[scheme+11]="X") then font_type:=mathex;
+  end;
+end
+
+@ @<Output the character coding scheme@>=
+left; out('CODINGSCHEME');
+out_BCPL(scheme);
+right
+
+@ @<Output the family name@>=
+left; out('FAMILY');
+check_BCPL(family,20);
+out_BCPL(family);
+right
+
+@ @<Output the rest of the header@>=
+begin left; out('FACE'); out_face(random_word+3); right;
+for i:=18 to lh-1 do
+  begin left; out('HEADER D ',i:1);
+  out_octal(check_sum+4*i,@,4); right;
+  end;
+end
+
+@ This program does not check to see if the |seven_bit_safe_flag| has the
+correct setting, i.e., if it really reflects the seven-bit-safety of
+the \.{TFM} file; the stated value is merely put into the \.{PL} file.
+The \.{PLtoTF} program will store a correct value and give a warning
+message if a file falsely claims to be safe.
+
+@<Output the |seven_bit_safe_flag|@>=
+if (lh>17) and (tfm[random_word]>127) then
+  begin left; out('SEVENBITSAFEFLAG TRUE'); right;
+  end
+
+@ The next thing to take care of is the list of parameters.
+
+@<Do the parameters@>=
+if np>0 then
+  begin left; out('FONTDIMEN'); out_ln;
+  for i:=1 to np do @<Check and output the $i$th parameter@>;
+  right;
+  end;
+@<Check to see if |np| is complete for this font type@>;
+
+@ @<Check to see if |np|...@>=
+if (font_type=mathsy)and(np<>22) then
+  print_ln('Unusual number of fontdimen parameters for a math symbols font (',
+@.Unusual number of fontdimen...@>
+    np:1,' not 22).')
+else if (font_type=mathex)and(np<>13) then
+  print_ln('Unusual number of fontdimen parameters for an extension font (',
+    np:1,' not 13).')
+
+@ All |fix_word| values except the design size and the first parameter
+will be checked to make sure that they are less than 16.0 in magnitude,
+using the |check_fix| macro:
+
+@d check_fix_tail(#)==bad(#,' ',i:1,' is too big;');
+  print_ln('I have set it to zero.');
+  end
+@d check_fix(#)==if (tfm[#]>0)and(tfm[#]<255) then
+  begin tfm[#]:=0; tfm[(#)+1]:=0; tfm[(#)+2]:=0; tfm[(#)+3]:=0;
+  check_fix_tail
+
+@<Check and output the $i$th parameter@>=
+begin left;
+if i=1 then out('SLANT') {this parameter is not checked}
+else  begin check_fix(param(i))('Parameter');@/
+@.Parameter n is too big@>
+  @<Output the name of parameter $i$@>;
+  end;
+out_fix(param(i)); right;
+end
+
+@ @<Output the name...@>=
+if i<=7 then case i of
+  2:out('SPACE');@+3:out('STRETCH');@+4:out('SHRINK');
+  5:out('XHEIGHT');@+6:out('QUAD');@+7:out('EXTRASPACE')@+end
+else if (i<=22)and(font_type=mathsy) then case i of
+  8:out('NUM1');@+9:out('NUM2');@+10:out('NUM3');
+  11:out('DENOM1');@+12:out('DENOM2');
+  13:out('SUP1');@+14:out('SUP2');@+15:out('SUP3');
+  16:out('SUB1');@+17:out('SUB2');
+  18:out('SUPDROP');@+19:out('SUBDROP');
+  20:out('DELIM1');@+21:out('DELIM2');
+  22:out('AXISHEIGHT')@+end
+else if (i<=13)and(font_type=mathex) then
+  if i=8 then out('DEFAULTRULETHICKNESS')
+  else out('BIGOPSPACING',i-8:1)
+else out('PARAMETER D ',i:1)
+
+@ We need to check the range of all the remaining |fix_word| values,
+and to make sure that |width[0]=0|, etc.
+
+@d nonzero_fix(#)==(tfm[#]>0)or(tfm[#+1]>0)or(tfm[#+2]>0)or(tfm[#+3]>0)
+
+@<Check the |fix_word| entries@>=
+if nonzero_fix(4*width_base) then bad('width[0] should be zero.');
+@.should be zero@>
+if nonzero_fix(4*height_base) then bad('height[0] should be zero.');
+if nonzero_fix(4*depth_base) then bad('depth[0] should be zero.');
+if nonzero_fix(4*italic_base) then bad('italic[0] should be zero.');
+for i:=0 to nw-1 do check_fix(4*(width_base+i))('Width');
+@.Width n is too big@>
+for i:=0 to nh-1 do check_fix(4*(height_base+i))('Height');
+@.Height n is too big@>
+for i:=0 to nd-1 do check_fix(4*(depth_base+i))('Depth');
+@.Depth n is too big@>
+for i:=0 to ni-1 do check_fix(4*(italic_base+i))('Italic correction');
+@.Italic correction n is too big@>
+if nk>0 then for i:=0 to nk-1 do check_fix(kern(i))('Kern');
+@.Kern n is too big@>
+
+@ The ligature/kerning program comes next. Before we can put it out in
+\.{PL} format, we need to make a table of ``labels'' that will be inserted
+into the program. For each character |c| whose |tag| is |lig_tag| and
+whose starting address is |r|, we will store the pair |(c,r)| in the
+|label_table| array. If there's a boundary-char program starting at~|r|,
+we also store the pair |(256,r)|.
+This array is sorted by its second components, using the
+simple method of straight insertion.
+
+@<Glob...@>=
+@!label_table:array[0..258] of record@t@>@/@!cc:0..256;@!rr:0..lig_size;end;
+@!label_ptr: 0..257; {the largest entry in |label_table|}
+@!sort_ptr:0..257; {index into |label_table|}
+@!boundary_char:0..256; {boundary character, or 256 if none}
+@!bchar_label:0..@'77777; {beginning of boundary character program}
+
+@ @<Set init...@>=
+boundary_char:=256; bchar_label:=@'77777;@/
+label_ptr:=0; label_table[0].rr:=0; {a sentinel appears at the bottom}
+
+@ We'll also identify and remove inaccessible program steps, using the
+|activity| array.
+
+@d unreachable=0 {a program step not known to be reachable}
+@d pass_through=1 {a program step passed through on initialization}
+@d accessible=2 {a program step that can be relevant}
+
+@<Glob...@>=
+@!activity:array[0..lig_size] of unreachable..accessible;
+@!ai,@!acti:0..lig_size; {indices into |activity|}
+
+@ @<Do the ligatures and kerns@>=
+if nl>0 then
+  begin for ai:=0 to nl-1 do activity[ai]:=unreachable;
+  @<Check for a boundary char@>;
+  end;
+@<Build the label table@>;
+if nl>0 then
+  begin left; out('LIGTABLE'); out_ln;@/
+  @<Compute the |activity| array@>;
+  @<Output and correct the ligature/kern program@>;
+  right;
+  @<Check for ligature cycles@>;
+  end
+
+@ We build the label table even when |nl=0|, because this catches errors
+that would not otherwise be detected.
+
+@<Build...@>=
+for c:=bc to ec do if tag(c)=lig_tag then
+  begin r:=remainder(c);
+  if r<nl then
+    begin if tfm[lig_step(r)]>stop_flag then
+      begin r:=256*tfm[lig_step(r)+2]+tfm[lig_step(r)+3];
+      if r<nl then if activity[remainder(c)]=unreachable then
+        activity[remainder(c)]:=pass_through;
+      end;
+    end;
+  if r>=nl then
+    begin perfect:=false; print_ln(' ');
+    print('Ligature/kern starting index for character '); print_octal(c);
+    print_ln(' is too large;'); print_ln('so I removed it.'); reset_tag(c);
+@.Ligature/kern starting index...@>
+    end
+  else @<Insert |(c,r)| into |label_table|@>;
+  end;
+label_table[label_ptr+1].rr:=lig_size; {put ``infinite'' sentinel at the end}
+
+@ @<Insert |(c,r)|...@>=
+begin sort_ptr:=label_ptr; {there's a hole at position |sort_ptr+1|}
+while label_table[sort_ptr].rr>r do
+  begin label_table[sort_ptr+1]:=label_table[sort_ptr];
+  decr(sort_ptr); {move the hole}
+  end;
+label_table[sort_ptr+1].cc:=c;
+label_table[sort_ptr+1].rr:=r; {fill the hole}
+incr(label_ptr); activity[r]:=accessible;
+end
+
+@ @<Check for a bound...@>=
+if tfm[lig_step(0)]=255 then
+  begin left; out('BOUNDARYCHAR');
+  boundary_char:=tfm[lig_step(0)+1]; out_char(boundary_char); right;
+  activity[0]:=pass_through;
+  end;
+if tfm[lig_step(nl-1)]=255 then
+  begin r:=256*tfm[lig_step(nl-1)+2]+tfm[lig_step(nl-1)+3];
+  if r>=nl then
+    begin perfect:=false; print_ln(' ');
+    print('Ligature/kern starting index for boundarychar is too large;');
+    print_ln('so I removed it.');
+@.Ligature/kern starting index...@>
+    end
+  else begin label_ptr:=1; label_table[1].cc:=256; label_table[1].rr:=r;
+    bchar_label:=r; activity[r]:=accessible;
+    end;
+  activity[nl-1]:=pass_through;
+  end
+
+@ @<Compute the |activity| array@>=
+for ai:=0 to nl-1 do if activity[ai]=accessible then
+  begin r:=tfm[lig_step(ai)];
+  if r<stop_flag then
+    begin r:=r+ai+1;
+    if r>=nl then
+      begin bad('Ligature/kern step ',ai:1,' skips too far;');
+@.Lig...skips too far@>
+      print_ln('I made it stop.'); tfm[lig_step(ai)]:=stop_flag;
+      end
+    else activity[r]:=accessible;
+    end;
+  end
+
+@ We ignore |pass_through| items, which don't need to be mentioned in
+the \.{PL} file.
+
+@<Output and correct the ligature...@>=
+sort_ptr:=1; {point to the next label that will be needed}
+for acti:=0 to nl-1 do if activity[acti]<>pass_through then
+  begin i:=acti; @<Take care of commenting out unreachable steps@>;
+  @<Output any labels for step $i$@>;
+  @<Output step $i$ of the ligature/kern program@>;
+  end;
+if level=2 then right {the final step was unreachable}
+
+@ @<Output any labels...@>=
+while i=label_table[sort_ptr].rr do
+  begin left; out('LABEL');
+  if label_table[sort_ptr].cc=256 then out(' BOUNDARYCHAR')
+  else out_char(label_table[sort_ptr].cc);
+  right; incr(sort_ptr);
+  end
+
+@ @<Take care of commenting out...@>=
+if activity[i]=unreachable then
+  begin if level=1 then
+    begin left; out('COMMENT THIS PART OF THE PROGRAM IS NEVER USED!'); out_ln;
+    end
+  end
+else if level=2 then right
+
+@ @<Output step $i$...@>=
+begin k:=lig_step(i);
+if tfm[k]>stop_flag then
+  begin if 256*tfm[k+2]+tfm[k+3]>=nl then
+    bad('Ligature unconditional stop command address is too big.');
+@.Ligature unconditional stop...@>
+  end
+else if tfm[k+2]>=kern_flag then @<Output a kern step@>
+else @<Output a ligature step@>;
+if tfm[k]>0 then
+  if level=1 then @<Output either \.{SKIP} or \.{STOP}@>;
+end
+
+@ The \.{SKIP} command is a bit tricky, because we will be omitting all
+inaccessible commands.
+
+@<Output either...@>=
+begin if tfm[k]>=stop_flag then out('(STOP)')
+else begin count:=0;
+  for ai:=i+1 to i+tfm[k] do if activity[ai]=accessible then incr(count);
+  out('(SKIP D ',count:1,')'); {possibly $count=0$, so who cares}
+  end;
+out_ln;
+end
+
+@ @<Output a kern step@>=
+begin if nonexistent(tfm[k+1]) then if tfm[k+1]<>boundary_char then
+  correct_bad_char('Kern step for')(k+1);
+@.Kern step for nonexistent...@>
+left; out('KRN'); out_char(tfm[k+1]);
+r:=256*(tfm[k+2]-kern_flag)+tfm[k+3];
+if r>=nk then
+  begin bad('Kern index too large.');
+@.Kern index too large@>
+  out(' R 0.0');
+  end
+else out_fix(kern(r));
+right;
+end
+
+@ @<Output a ligature step@>=
+begin if nonexistent(tfm[k+1]) then if tfm[k+1]<>boundary_char then
+  correct_bad_char('Ligature step for')(k+1);
+@.Ligature step for nonexistent...@>
+if nonexistent(tfm[k+3]) then
+  correct_bad_char('Ligature step produces the')(k+3);
+@.Ligature step produces...@>
+left; r:=tfm[k+2];
+if (r=4)or((r>7)and(r<>11)) then
+  begin print_ln('Ligature step with nonstandard code changed to LIG');
+  r:=0; tfm[k+2]:=0;
+  end;
+if r mod 4>1 then out('/');
+out('LIG');
+if odd(r) then out('/');
+while r>3 do
+  begin out('>'); r:=r-4;
+  end;
+out_char(tfm[k+1]); out_char(tfm[k+3]); right;
+end
+
+@ The last thing on \.{TFtoPL}'s agenda is to go through the
+list of |char_info| and spew out the information about each individual
+character.
+
+@<Do the characters@>=
+sort_ptr:=0; {this will suppress `\.{STOP}' lines in ligature comments}
+for c:=bc to ec do if width_index(c)>0 then
+  begin if chars_on_line=8 then
+    begin print_ln(' '); chars_on_line:=1;
+    end
+  else  begin if chars_on_line>0 then print(' ');
+    incr(chars_on_line);
+    end;
+  print_octal(c); {progress report}
+  left; out('CHARACTER'); out_char(c); out_ln;
+  @<Output the character's width@>;
+  if height_index(c)>0 then @<Output the character's height@>;
+  if depth_index(c)>0 then @<Output the character's depth@>;
+  if italic_index(c)>0 then @<Output the italic correction@>;
+  case tag(c) of
+  no_tag: do_nothing;
+  lig_tag: @<Output the applicable part of the ligature/kern
+    program as a comment@>;
+  list_tag: @<Output the character link unless there is a problem@>;
+  ext_tag: @<Output an extensible character recipe@>;
+  end; {there are no other cases}
+  right;
+  end
+
+@ @<Output the character's width@>=
+begin left; out('CHARWD');
+if width_index(c)>=nw then range_error('Width')
+else out_fix(width(c));
+right;
+end
+
+@ @<Output the character's height@>=
+if height_index(c)>=nh then range_error('Height')
+@.Height index for char...@>
+else  begin left; out('CHARHT'); out_fix(height(c)); right;
+  end
+
+@ @<Output the character's depth@>=
+if depth_index(c)>=nd then range_error('Depth')
+@.Depth index for char@>
+else  begin left; out('CHARDP'); out_fix(depth(c)); right;
+  end
+
+@ @<Output the italic correction@>=
+if italic_index(c)>=ni then range_error('Italic correction')
+@.Italic correction index for char...@>
+else  begin left; out('CHARIC'); out_fix(italic(c)); right;
+  end
+
+@ @<Output the applicable part of the ligature...@>=
+begin left; out('COMMENT'); out_ln;@/
+i:=remainder(c); r:=lig_step(i);
+if tfm[r]>stop_flag then i:=256*tfm[r+2]+tfm[r+3];
+repeat @<Output step...@>;
+if tfm[k]>=stop_flag then i:=nl
+else i:=i+1+tfm[k];
+until i>=nl;
+right;
+end
+
+@ We want to make sure that there is no cycle of characters linked together
+by |list_tag| entries, since \TeX\ doesn't want to risk endless loops.
+If such a cycle exists, the routine here detects it when processing
+the largest character code in the cycle.
+
+@<Output the character link unless there is a problem@>=
+begin r:=remainder(c);
+if nonexistent(r) then
+  begin bad_char('Character list link to')(r); reset_tag(c);
+@.Character list link...@>
+  end
+else  begin while (r<c)and(tag(r)=list_tag) do r:=remainder(r);
+  if r=c then
+    begin bad('Cycle in a character list!');
+@.Cycle in a character list@>
+    print('Character '); print_octal(c);
+    print_ln(' now ends the list.');
+    reset_tag(c);
+    end
+  else  begin left; out('NEXTLARGER'); out_char(remainder(c));
+    right;
+    end;
+  end;
+end
+
+@ @<Output an extensible character recipe@>=
+if remainder(c)>=ne then
+  begin range_error('Extensible'); reset_tag(c);
+@.Extensible index for char@>
+  end
+else  begin left; out('VARCHAR'); out_ln;
+  @<Output the extensible pieces that exist@>;
+  right;
+  end
+
+@ @<Output the extensible pieces that...@>=
+for k:=0 to 3 do if (k=3)or(tfm[exten(c)+k]>0) then
+  begin left;
+  case k of
+  0:out('TOP');@+1:out('MID');@+2:out('BOT');@+3:out('REP')@+end;
+  if nonexistent(tfm[exten(c)+k]) then out_char(c)
+  else out_char(tfm[exten(c)+k]);
+  right;
+  end
+
+@ Some of the extensible recipes may not actually be used, but \TeX\ will
+complain about them anyway if they refer to nonexistent characters.
+Therefore \.{TFtoPL} must check them too.
+
+@<Check the extensible recipes@>=
+if ne>0 then for c:=0 to ne-1 do for d:=0 to 3 do
+  begin k:=4*(exten_base+c)+d;
+  if (tfm[k]>0)or(d=3) then
+    begin if nonexistent(tfm[k]) then
+      begin bad_char('Extensible recipe involves the')(tfm[k]);
+@.Extensible recipe involves...@>
+      if d<3 then tfm[k]:=0;
+      end;
+    end;
+  end
+
+@* Checking for ligature loops.
+We have programmed almost everything but the most interesting calculation of
+all, which has been saved for last as a special treat. \TeX's extended ligature
+mechanism allows unwary users to specify sequences of ligature replacements
+that never terminate. For example, the pair of commands
+$$\.{(/LIG $x$ $y$) (/LIG $y$ $x$)}$$
+alternately replaces character $x$ by character $y$ and vice versa. A similar
+loop occurs if \.{(LIG/ $z$ $y$)} occurs in the program for $x$ and
+ \.{(LIG/ $z$ $x$)} occurs in the program for $y$.
+
+More complicated loops are also possible. For example, suppose the ligature
+programs for $x$ and $y$ are
+$$\vcenter{\halign{#\hfil\cr
+\.{(LABEL $x$)(/LIG/ $z$ $w$)(/LIG/> $w$ $y$)} \dots,\cr
+\.{(LABEL $y$)(LIG $w$ $x$)} \dots;\cr}}$$
+then the adjacent characters $xz$ change to $xwz$, $xywz$, $xxz$, $xxwz$,
+\dots, ad infinitum.
+
+@ To detect such loops, \.{TFtoPL} attempts to evaluate the function
+$f(x,y)$ for all character pairs $x$ and~$y$, where $f$ is defined as
+follows: If the current character is $x$ and the next character is
+$y$, we say the ``cursor'' is between $x$ and $y$; when the cursor
+first moves past $y$, the character immediately to its left is
+$f(x,y)$. This function is defined if and only if no infinite loop is
+generated when the cursor is between $x$ and~$y$.
+
+The function $f(x,y)$ can be defined recursively. It turns out that all pairs
+$(x,y)$ belong to one of five classes. The simplest class has $f(x,y)=y$; this
+happens if there's no ligature between $x$ and $y$, or in the cases
+\.{LIG/>} and \.{/LIG/>>}. Another simple class arises when there's a
+\.{LIG} or \.{/LIG>} between $x$ and~$y$, generating the character~$z$;
+then $f(x,y)=z$. Otherwise we always have $f(x,y)$ equal to
+either $f(x,z)$ or $f(z,y)$ or $f(f(x,z),y)$, where $z$ is the inserted
+ligature character.
+
+The first two of these classes can be merged; we can also consider
+$(x,y)$ to belong to the simple class when $f(x,y)$ has been evaluated.
+For technical reasons we allow $x$ to be 256 (for the boundary character
+at the left) or 257 (in cases when an error has been detected).
+
+For each pair $(x,y)$ having a ligature program step, we store
+$(x,y)$ in a hash table from which the values $z$ and $class$ can be read.
+
+@d simple=0 {$f(x,y)=z$}
+@d left_z=1 {$f(x,y)=f(z,y)$}
+@d right_z=2 {$f(x,y)=f(x,z)$}
+@d both_z=3 {$f(x,y)=f(f(x,z),y)$}
+@d pending=4 {$f(x,y)$ is being evaluated}
+
+@<Glob...@>=
+@!hash:array[0..hash_size] of 0..66048; {$256x+y+1$ for $x\le257$ and $y\le255$}
+@!class:array[0..hash_size] of simple..pending;
+@!lig_z:array[0..hash_size] of 0..257;
+@!hash_ptr:0..hash_size; {the number of nonzero entries in |hash|}
+@!hash_list:array[0..hash_size] of 0..hash_size; {list of those nonzero entries}
+@!h,@!hh:0..hash_size; {indices into the hash table}
+@!x_lig_cycle,@!y_lig_cycle:0..256; {problematic ligature pair}
+
+@ @<Check for ligature cycles@>=
+hash_ptr:=0; y_lig_cycle:=256;
+for hh:=0 to hash_size do hash[hh]:=0; {clear the hash table}
+for c:=bc to ec do if tag(c)=lig_tag then
+  begin i:=remainder(c);
+  if tfm[lig_step(i)]>stop_flag then
+    i:=256*tfm[lig_step(i)+2]+tfm[lig_step(i)+3];
+  @<Enter data for character $c$ starting at location |i| in the hash table@>;
+  end;
+if bchar_label<nl then
+  begin c:=256; i:=bchar_label;
+  @<Enter data for character $c$ starting at location |i| in the hash table@>;
+  end;
+if hash_ptr=hash_size then
+  begin print_ln('Sorry, I haven''t room for so many ligature/kern pairs!');
+@.Sorry, I haven't room...@>
+  goto final_end;
+  end;
+for hh:=1 to hash_ptr do
+  begin r:=hash_list[hh];
+  if class[r]>simple then {make sure $f$ is defined}
+     r:=f(r,(hash[r]-1)div 256,(hash[r]-1)mod 256);
+  end;
+if y_lig_cycle<256 then
+  begin  print('Infinite ligature loop starting with ');
+@.Infinite ligature loop...@>
+  if x_lig_cycle=256 then print('boundary')@+else print_octal(x_lig_cycle);
+  print(' and '); print_octal(y_lig_cycle); print_ln('!');
+  out('(INFINITE LIGATURE LOOP MUST BE BROKEN!)'); goto final_end;
+  end
+
+@ @<Enter data for character $c$...@>=
+repeat hash_input; k:=tfm[lig_step(i)];
+if k>=stop_flag then i:=nl
+else i:=i+1+k;
+until i>=nl
+
+@ We use an ``ordered hash table'' with linear probing, because such a table
+is efficient when the lookup of a random key tends to be unsuccessful.
+
+@p procedure hash_input; {enter data for character |c| and command |i|}
+label 30; {go here for a quick exit}
+var @!cc:simple..both_z; {class of data being entered}
+@!zz:0..255; {function value or ligature character being entered}
+@!y:0..255; {the character after the cursor}
+@!key:integer; {value to be stored in |hash|}
+@!t:integer; {temporary register for swapping}
+begin if hash_ptr=hash_size then goto 30;
+@<Compute the command parameters |y|, |cc|, and |zz|@>;
+key:=256*c+y+1; h:=(1009*key) mod hash_size;
+while hash[h]>0 do
+  begin if hash[h]<=key then
+    begin if hash[h]=key then goto 30; {unused ligature command}
+    t:=hash[h]; hash[h]:=key; key:=t; {do ordered-hash-table insertion}
+    t:=class[h]; class[h]:=cc; cc:=t; {namely, do a swap}
+    t:=lig_z[h]; lig_z[h]:=zz; zz:=t;
+    end;
+  if h>0 then decr(h)@+else h:=hash_size;
+  end;
+hash[h]:=key; class[h]:=cc; lig_z[h]:=zz;
+incr(hash_ptr); hash_list[hash_ptr]:=h;
+30:end;
+
+@ We must store kern commands as well as ligature commands, because the former
+might make the latter inapplicable.
+
+@<Compute the command param...@>=
+k:=lig_step(i); y:=tfm[k+1]; t:=tfm[k+2]; cc:=simple; zz:=tfm[k+3];
+if t>=kern_flag then zz:=y
+else begin case t of
+  0,6:do_nothing; {\.{LIG},\.{/LIG>}}
+  5,11:zz:=y; {\.{LIG/>}, \.{/LIG/>>}}
+  1,7:cc:=left_z; {\.{LIG/}, \.{/LIG/>}}
+  2:cc:=right_z; {\.{/LIG}}
+  3:cc:=both_z; {\.{/LIG/}}
+  end; {there are no other cases}
+  end
+
+@ Evaluation of $f(x,y)$ is handled by two mutually recursive procedures.
+Kind of a neat algorithm, generalizing a depth-first search.
+
+@p function f(@!h,@!x,@!y:index):index; forward;@t\2@>
+  {compute $f$ for arguments known to be in |hash[h]|}
+function eval(@!x,@!y:index):index; {compute $f(x,y)$ with hashtable lookup}
+var @!key:integer; {value sought in hash table}
+begin key:=256*x+y+1; h:=(1009*key) mod hash_size;
+while hash[h]>key do
+  if h>0 then decr(h)@+else h:=hash_size;
+if hash[h]<key then eval:=y {not in ordered hash table}
+else eval:=f(h,x,y);
+end;
+
+@ Pascal's beastly convention for |forward| declarations prevents us from
+saying |function f(h,x,y:index):index| here.
+
+@p function f;
+begin case class[h] of
+simple: do_nothing;
+left_z: begin class[h]:=pending; lig_z[h]:=eval(lig_z[h],y); class[h]:=simple;
+  end;
+right_z: begin class[h]:=pending; lig_z[h]:=eval(x,lig_z[h]); class[h]:=simple;
+  end;
+both_z: begin class[h]:=pending; lig_z[h]:=eval(eval(x,lig_z[h]),y);
+  class[h]:=simple;
+  end;
+pending: begin x_lig_cycle:=x; y_lig_cycle:=y; lig_z[h]:=257; class[h]:=simple;
+  end; {the value 257 will break all cycles, since it's not in |hash|}
+end; {there are no other cases}
+f:=lig_z[h];
+end;
+
+@* The main program.
+The routines sketched out so far need to be packaged into separate procedures,
+on some systems, since some \PASCAL\ compilers place a strict limit on the
+size of a routine. The packaging is done here in an attempt to avoid some
+system-dependent changes.
+
+First comes the |organize| procedure, which reads the input data and
+gets ready for subsequent events. If something goes wrong, the routine
+returns |false|.
+
+@p function organize:boolean;
+label final_end, 30;
+var tfm_ptr:index; {an index into |tfm|}
+begin @<Read the whole input file@>;@/
+@<Set subfile sizes |lh|, |bc|, \dots, |np|@>;@/
+@<Compute the base addresses@>;@/
+organize:=true; goto 30;
+final_end: organize:=false;
+30: end;
+
+@ Next we do the simple things.
+
+@p procedure do_simple_things;
+var i:0..@'77777; {an index to words of a subfile}
+begin @<Do the header@>;@/
+@<Do the parameters@>;@/
+@<Check the |fix_word| entries@>@/
+end;
+
+@ And then there's a routine for individual characters.
+
+@p procedure do_characters;
+var @!c:byte; {character being done}
+@!k:index; {a random index}
+@!ai:0..lig_size; {index into |activity|}
+begin @<Do the characters@>;@/
+end;
+
+@ Here is where \.{TFtoPL} begins and ends.
+@p begin initialize;@/
+if not organize then goto final_end;
+do_simple_things;@/
+@<Do the ligatures and kerns@>;
+@<Check the extensible recipes@>;
+do_characters; print_ln('.');@/
+if level<>0 then print_ln('This program isn''t working!');
+@.This program isn't working@>
+if not perfect then
+  begin out('(COMMENT THE TFM FILE WAS BAD, SO THE DATA HAS BEEN CHANGED!)');
+@.THE TFM FILE WAS BAD...@>
+  write_ln(pl_file);
+  end;
+final_end:end.
+
+@* System-dependent changes.
+This section should be replaced, if necessary, by changes to the program
+that are necessary to make \.{TFtoPL} work at a particular installation.
+It is usually best to design your change file so that all changes to
+previous sections preserve the section numbering; then everybody's version
+will be consistent with the printed program. More extensive changes,
+which introduce new sections, can be inserted here; then only the index
+itself will get a new section number.
+@^system dependencies@>
+
+@* Index.
+Pointers to error messages appear here together with the section numbers
+where each ident\-i\-fier is used.