{outline of declaration of subprograms:

 1.     program IndexText(InText, InIndex, NewIndex, OutIndex, HashFile,
                          NewHashFile, input, output);     (main program)
 2.         function Lt(u, v: word):  Boolean;
 3.         procedure ReadWord(var f: text;  var w: word);
 4.         procedure WriteWord(var f: text; w: word);
 4a.        built in CPU time function   clock;

 5.         procedure SplitWords;                       (phase 1)
 5a.            function FindFile(ch: char): filecode;
 6.             function HashAddress(w: word):  hashentry;
 7.             procedure Initialize;
 8.             procedure GetWord;
 8a.                procedure TellUserPage;
 9.                 procedure GetChar(var ch: char);
10.                 procedure AddChar(ch: char);
11.             procedure Conclude;

12.         procedure ClassifyWords;                    (phase 2)
13.             procedure BuildTree(var root: pointer; ch: char);
15.                 function Power2(c: integer): level;
                  (the next three procedures are written in line.)
14.                 procedure Insert(p: pointer);
16.                 procedure FindRoot;
17.                 procedure ConnectSubtrees;
18.                 procedure GetNode(var p: pointer; ch: char);
19.             procedure Process(r: reference);
20.                 procedure UpdateNode(p: pointer; r: reference);
21.                 procedure NewWord(var p: pointer; r: reference);
22.                 procedure InsertTree(r, p: pointer);
23.             procedure OutputTree(p: pointer);
24.                 procedure PutNode(p: pointer);
}



program IndexText(InText, InIndex, NewIndex, HashFile, NewHashFile,
                  input, output);

{Produces word counts and list of references for the document file 
 InText. Uses the master word list in file InIndex, if provided. Output word
 list for new text goes to file NewIndex. HashFile contains the common words
 to be ignored. If not specified, it is created on output, containing the
 words so flagged by the user.}
{This implementation uses only phases 1 and 2. A smaller array of text files
 is also used, as specified in the exercise section.}

const
  maxwd         =   20;             {More letters in word will be ignored.}
  minwd         =    1;                    {Shorter words will be ignored.}
  hashsize      = 2003;                                 {should be a prime}
  linesperpage  =   66;                {assumes standard spacing and paper}
  maxheight     =   20;               {for building binary tree in phase 2}
  A             =  'A';
  Z             =  'Z';
  hyphen        =  '-';
  blank         =  ' ';
  apostrophe    = '''';               {requires two `'s  to represent one}
  underscore    =  '_';
  ordbackspace  =    8;            {ASCII control character for backspace}
  ordformfeed   =   12;             {ASCII control character for new page}
  changecase    =   32;    {ASCII difference between upper and lower case}
  nfiles        =    8;  {number of temporary files for unprocessed words}
  MaxRowLength  =   130;                 {maximum length of output records}

type
  word          =  packed array[1..maxwd] of char;
  reference     =  record
                      wd:   word;
                      pg:   integer;               {count or page number}
                   end;
  fileref       =  file of reference;              {used for local files}
  letter        =  A..Z;
  hashentry     =  1..hashsize;
  filecode      =  1..nfiles;

var
  InText,                                     {document being processed}
  InIndex,                                            {master word list}
  NewIndex,                              {word list of current document}
  HashFile,
  NewHashFile:      text;
  RefFile:      array[filecode] of fileref; {local files used for auxilary
                               storage of words from phase 1 to phase 2:
                Normally, a separate file exist for each initial letter,
        this version uses nfiles files due operating system constraints.}
  blankword:    word;                           {will contain all blanks}

{The next two variables were originally declared in procedure SplitWords,
 they have been moved to this level in order to access them globally.}
  outcount:     array[filecode] of integer;    {counters for word  files}
  wordcount:    integer;                 {count of all words in the text}

  intextname,
  inlistname,
  newlistname,
  newhashname:  word;                    {used to get filename from user}
  lastletter:   array[filecode] of letter;     {last letter in each file}
  PresentTime,
  StartTime:    integer;                         {used to track CPU time}
  RowLength:    integer;   {ensures records will not exceed MaxRowLength}


function Lt( u, v: word): Boolean;
{Determains if word u precedes word v lexicographically.}
begin
  Lt := (u < v)
end;

procedure ReadWord( var F: text;  var w: word);
{Reads word w from text file F.  Assumes not at end of file.}
{Uses packed array, replace using a loop if your system does not 
 support packed arrays. }
begin                           {procedure ReadWord}
  read(F, w)
end;                            {procedure ReadWord}

procedure WriteWord( var F: text; w: word);
{Writes word w to text file F}
{Uses packed array, replace using a loop if your system does not 
 support packed arrays. }
begin                           {procedure WriteWord}
  write(F, w)
end;                            {procedure WriteWord}

procedure SetTimer;     {Call once at beginning of program execution.}
{Finds the CPU time when called, and keeps in variables for reference.}
{System dependent procedure.}
begin
  PresentTime := clock;
  StartTime := PresentTime;
end;

function TotalTime:  real;
{Returns the total CPU time, in seconds, since call to SetTimer.}
{System dependent procedure.}
begin
  TotalTime := (clock - StartTime) / 1000.0;
end;

function ElapsedTime:  real;
{Returns elapsed CPU time since last call to function ElapsedTime,
 or call to SetTimer, whichever is more recent.}
{System dependent procedure.}
var r: integer;
begin
  r := clock;
  ElapsedTime := (r - PresentTime) / 1000.0;
  PresentTime := r;
end;



procedure SplitWords;
{sets up hash table, reads text, and divides into nfiles word lists}

var
  hash:       array[hashentry] of word;              {hash table}
  pagecount:  integer;                 {keeps the current page number}
  addpage:    integer;       {amount to increase pagecount after word}
  linecount:  integer;                     {lines on the current page}
  w:          word;                   {word currently being processed}
  x:          hashentry;             {location of w, if in hash table}
  endinput:   Boolean;   {true if and only if input has all been read}
  code:       filecode;                {into which file does word go?}

{The following variables are kept for use in procedure GetWord, and for
 efficiency are set up only once in procedure Initialize:}
  backspace,
  formfeed:   char;
  alphabet,                           {letters only - to start a word}
  contchar:   set of char;     {other characters ok in middle of word}


  function  FindFile( ch:  letter):  filecode;
  {Uses binary decision tree to select one of nfiles = 8 files depending
   on the letter ch.  These letters must be the same as those in the
   global array  lastletter  .}
  begin                           {function FindFile}
    if            ch < 'M' then
      if          ch < 'E' then
        if        ch < 'C' then  FindFile := 1
                           else  FindFile := 2
      else if     ch < 'H' then  FindFile := 3
                           else  FindFile := 4
    else if       ch < 'S' then
      if          ch < 'P' then  FindFile := 5
                           else  FindFile := 6
      else if     ch < 'T' then  FindFile := 7
                           else  FindFile := 8
  end;                            {function FindFile}


  function HashAddress(w: word): hashentry;   {modified from textbook}
  {calculates the location in hash table of word w, or, if not there,
   returns pointing to the blank word where w should go}

  var
    x,                            {calculated location}
    inc:     integer;             {increment for open addressing}
  begin                           {function HashAddress}
    x := abs(ord(w[1])*ord(w[2])+ord(w[4])+ord(w[6])) mod hashsize + 1;
{Hash function assumes long word length. For short word machines
 we must ensure that the result is non-negative, and worry about overflow.}

    if (hash[x] <> w) and (hash[x] <> blankword) then
      begin
        inc   := (abs(ord(w[3])-95) mod 29);
                  {A key dependent increment is used to avoid clustering.}
        repeat
          inc := inc + 1;
          if inc > hashsize then
            writeln(w,' causes hash table to become full, infinite loop.');
          x := x + inc;
          if x > hashsize then x := x - hashsize;
        until (w =  hash[x])  or  (blankword = hash[x])
      end;
    HashAddress := x
  end;                            {function HashAddress}


  procedure Initialize;
  {sets up constant-valued sets for use in GetWord. Opens the text file
   and initializes various counters. Opens file holding hash table (if any),
   and reads or otherwise initializes table}
  var
    i:         integer;          {general purpose loop control}

  begin                           {procedure Initialize}
    backspace:= chr(ordbackspace);
    formfeed := chr(ordformfeed); {initialize ASCII control characters}
    alphabet := ['A'..'Z', 'a'..'z'];      {letters only, to start a word}
    contchar := [hyphen, apostrophe, backspace, underscore];
                                {characters which will not terminate word}
    for i := 1 to maxwd do
      blankword[i] := blank;

    write('Name of input text file?');
    ReadWord(input, intextname); readln;
    open(InText, intextname, readonly);
    reset(InText);
    endinput := eof(InText);

    repeat
      write( 'What is the page number on which the text begins?');
      readln(pagecount);
      if pagecount < 0 then
        writeln('Must be a non-negative integer.')
    until pagecount >= 0;
    linecount := 0;
    addpage   := 0;
    wordcount := 0;

    for i := 1 to nfiles do
    begin
      rewrite( RefFile[i] );
      outcount[i] := 0
    end;
    lastletter[1] := 'B';
    lastletter[2] := 'D';
    lastletter[3] := 'G';
    lastletter[4] := 'L';
    lastletter[5] := 'O';
    lastletter[6] := 'R';
    lastletter[7] := 'S';
    lastletter[8] := 'Z';

    reset(HashFile);   {assumes HASHFILE.DAT is in current directory}
    if eof(HashFile) then
    begin     {There is no previous table; initialize the table to all blanks.}
      writeln('Cannot open file for hash table. Creating a new table.');
      for i := 1 to hashsize do
        hash[i] := blankword
    end
    else begin                 {Retrieve the previous hash table.}
      i := 0;
      repeat
        i := i + 1;
        hash[i] := HashFile^;
        get(HashFile)
      until eof(HashFile) or (i >= hashsize);
      if (not eof(HashFile)) or (i <> hashsize) then
        writeln('Error in reading hash table. Incorrect number of entries.')
    end
end;                                        {procedure Initialize}



  procedure GetWord( var  w: word);
  {Gets words from input file InText, and returns only words
   at least minwd characters long.  Parameter endinput becomes
   true if and only if the end of InText is reached with no word to return.
   the procedure also updates global variables wordcount and linecount,
   updates the global variable pagecount after each linesperpage cr's,
   or after each formfeed, whichever comes first, and
   uses the sets alphabet and contchar and various character constants.}

  label 1;           {used by GetChar to exit procedure upon eof(InText)}

  var  c:      0..maxwd;                    {count of characters in word}
       ch:     char;                      {character currently processed}
       endln:  Boolean;                           {at the end of a line?}


  procedure TellUserPage;         {keep the user informed of progress}
  var   i: integer;
  begin
    i := pagecount + addpage;
    writeln('At page', i:4, ' word count is', wordcount:7)
  end;


  procedure GetChar(var ch: char);
  {gets a character from input text into ch; checks for eof; updates
   page count and line count}

  begin                                                {procedure GetChar}
    if eof(InText) then
      if c >= minwd then
        ch := '.'              {special character to end the current word}
      else begin                         {no word to return; set endinput}
        endinput := true;
        goto 1                                        {exit from GetWord.}
      end
    else begin                   {not end of file: process next character}
      while InText^ in [underscore, backspace] do
        get( InText);
      ch := InText^;
      endln := eoln(InText);
      get(InText);
      if endln then
      begin
        linecount := linecount + 1;
        if linecount >= linesperpage then
          begin
            addpage := addpage + 1;
            linecount := 0;
            TellUserPage
          end
      end;
      if ch = formfeed then
        begin
          addpage := addpage + 1;
          linecount := 0;
          TellUserPage;
          endln := true;            {Treat formfeed like end of line.}
          ch := blank
        end
    end
  end;                                            {procedure GetChar}


  procedure AddChar(ch: char);
  {adds given character to word, if possible}
  begin                           {procedure AddChar}
    if c < maxwd then
    begin
      c := c + 1;
      w[c] := ch
    end
  end;                            {procedure AddChar}


  begin                           {procedure GetWord}
    repeat                {until current word is at least minwd chars long}
      c := 0;
      repeat
        GetChar(ch)               {Find a letter which will start the word.}
      until ch in alphabet;
      pagecount := pagecount + addpage;
      addpage := 0;
      if ch in ['a'..'z'] then       {translate first letter to upper case.}
        ch := chr(ord(ch) - changecase); {assumes ASCII ordering of letters}
      AddChar(ch);                          {put first letter into the word}
      GetChar(ch);
      while (ch in alphabet) or (ch in contchar) do
        if ch in alphabet then                {add letters directly to word}
        begin                                            {processing letter}
          AddChar(ch);
          GetChar(ch)
        end                                              {processing letter}
        else if ch = hyphen then
        begin                                            {processing hyphen}
          GetChar(ch);                       {Find what comes after hyphen.}
          if endln then
            while ch = ' ' do
              GetChar(ch)       {Delete both the hyphen and the end of line}
          else if ch = hyphen then      {Two hyphens form a dash; ends word}
            ch := blank                 {Use a blank to terminate the word.}
          else if ch in alphabet then
            AddChar(hyphen)                  {Include other hyphens in word}
          else      {nothing}
        end                                              {processing hyphen}
        else if ch = apostrophe then
        begin                                        {processing apostrophe}
          GetChar(ch);
          if ch = 's' then              {Delete  `'s'   at end of word only}
          begin
            GetChar(ch);
            if ch in contchar then
            begin
              AddChar(apostrophe);
              AddChar('s')
            end
          end
          else if ch in alphabet then
             AddChar(apostrophe)                      {Allow contractions.}
        end                                         {processing apostrophe}
        else         {Remaining possibilities are backspace and underscore.}
          GetChar(ch);                           {Delete these characters.}
      {While loop on continuing characters ends here.}
      wordcount := wordcount + 1
    until c >= minwd;                              {Skip over short words.}

    while c < maxwd do                                  {Fill with blanks.}
    begin
      c := c + 1;
      w[c] := blank
    end;
  1:      {When end of file occurs, program will exit to here from GetChar}
  end;                                                  {procedure GetWord}



procedure Conclude;
{Writes out counts of various word lists. For some systems, it is 
 necessary to close files, which should be done here.}
var
  i: integer;                                                 {loop index}
begin                                                 {procedure Conclude}
  writeln('The total number of words read in is ', wordcount:7);
  writeln;
  writeln('The number of words to process further in the next stage,');
  writeln('in each temporary file, is below.');
  writeln('     a-b     c-d     e-g     h-l     m-o     p-r      s      t-z');
  for i := 1 to nfiles do
    write(outcount[i]:8);
  writeln;
  writeln
end;                                                  {procedure Conclude}



begin                                          {procedure  SplitWords}
  Initialize;                   {sets up files, hash table, constants}
  GetWord(w);                       {obtain a single word from InText}
  while not endinput do
  begin
    x := HashAddress(w);
    if w <> hash[x] then
    begin
      code := FindFile( w[1] );
      outcount[code] := outcount[code] + 1;
      with RefFile[code]^ do
      begin
        wd := w;
        pg := pagecount
      end;
      Put(RefFile[code])
    end;
    GetWord(w)
  end;
  Conclude                           {writes word counts to output.}
end;                                          {procedure SplitWords}





{start of phase 2}

procedure ClassifyWords;
{For each letter of the alphabet, the procedure reads in a list of
 words from InIndex, builds them into a binary tree, supplements it
 with entries from RefFile, and writes the result to files NewIndex
 and NewHashFile.}

type
  wordtype  = (hash, count, page, question, index); {ways to process a word}
  pointref  = ^reflist;
  reflist   = record                            {list of references}
                pg:   integer;
                next: pointref
              end;
  pointer   = ^node;
  node      = record                    {vertex of the binary tree}
                wd:       word;
                left,
                right:    pointer;
                ct:       integer;
                case kind:  wordtype of
                  hash, count:
                    ();
                  page, question, index:
                    (ref:   pointref)
              end;
var
  root:       pointer;                    {root of binary tree}
  code:       filecode;          {loop through temporary files}
  endlist:    Boolean;             {at end of input word list?}
  i:          integer;          {general purpose loop variable}



procedure BuildTree(var root: pointer;  code: filecode);

{Reads a sequential file in alphabetical order, and converts it into
 a binary search tree. Stops reading when the first letter of word
 is after lastletter[code].
 const  maxheight = 20  (in main program) allows 512k entries.}

{This procedure was modified slightly to fit the needs of this application.
 The parameters of GetNode now include a character ch, which has also
 been introduced as a local variable.}

type
  level = -1 .. maxheight;      {number of steps above leaves}

var
  lastnode:  array[level] of pointer;   {contains pointer to
                         last node processed on each level}
  counter:   integer;           {number of nodes read in so far}
  p:         pointer;           {p^ is present input node}
  lev:       level;             {level of p^}
  ch:        char;              {will be last letter to be processed.}


  function Power2(c:  integer): level;
  {finds the highest power of 2 which divides c}
  var
    lev:   level;
  begin                           {function Power2}
    lev := 0;
    while not odd(c) do
    begin
      c := c div 2;
      lev := lev + 1
    end;
    Power2 := lev
  end;                            {function Power2}


  procedure Insert(p: pointer);
  {Inserts p^ as rightmost node of a partial binary search tree.}
  var
    lev:       level;      {level of p^}
  begin                    {Procedure Insert}
    lev      := Power2(counter);
    p^.right := nil;
    p^.left  := lastnode[lev - 1];
    lastnode[lev] := p;
    if lastnode[lev + 1] <> nil then
      with lastnode[lev + 1]^ do
      if right = nil then right := p
  end;                     {Procedure Insert}


  procedure FindRoot;
  var
    lev:    level;
  begin                    {Procedure FindRoot}
    if counter = 0 then
      root := nil          {Tree is empty.}
    else begin             {Non-empty tree}
      lev := maxheight;    {Find the highest occupied level; it gives the root}
      while lastnode[lev] = nil do lev := lev - 1;
      root := lastnode[lev]
    end
  end;                     {Procedure FindRoot}


  procedure ConnectSubtrees;
  var
    p:         pointer;
    lev:       level;
    s:         level;
  begin                    {Procedure ConnectSubtrees}
    lev := maxheight;
    while (lastnode[lev] = nil) and (lev > 1) do
      lev := lev - 1;      {Find the highest node:  root}
    while lev > 1 do       {Nodes on levels 1 and 0 are already OK}
      with lastnode[lev]^ do
      if right <> nil then
        lev := lev - 1     {Search down for the highest dangling node}
      else begin           {Case:  right subtree is undefined.}
        p := left;         {Find the highest entry in lastnode that}
        s := lev - 1;                     {is not in the left subtree.}
        repeat
          p := p^.right;
          s := s - 1
        until (p = nil) or (p <> lastnode[s]);
        right := lastnode[s];
        lev := s           {Nodes on levels between lev and s are on the left.}
      end                  {Connecting dangling subtrees}
  end;                     {Procedure  ConnectSubtrees}


  procedure GetNode( var p: pointer;  ch:  char);
  {reads a word from file  InIndex  and sets node correspondingly}
  {returns p = nil at eof or when next word starts later than code.}
  var
    wordcode:  char;                {letter indicating type of word}

  begin                                          {procedure GetNode}
    while InIndex^ = '&' do         {ignore lines starting with '&'}
      readln(InIndex);
    while (not eof(InIndex)) and (InIndex^ = blank) do
      get(InIndex);                        {Skip all leading blanks}
    if endlist or eof(InIndex) then
      p := nil
    else if InIndex^ > ch then
      p := nil
   else begin
      new(p);
      with p^ do begin
        ReadWord(InIndex, wd);
        while (InIndex^ = ' ') and (not eoln(InIndex)) do
          get(InIndex);
        read(InIndex, wordcode);
        ct := 0;
        if wordcode in ['C', 'H','I','P','?'] then
        case wordcode of
          'C':  kind := count;

          'H':  begin
                  writeln('Warning: The input word list contains ', wd);
                  writeln('         which belongs in the hash table.');
                  kind := hash
                end;

          'I':  begin kind := index;     ref := nil  end;
          'P':  begin kind := page;      ref := nil  end;
          '?':  begin
                  writeln('Questionable word: ', wd, ' in word list.');
                  write('New category (P, I, C, H, ?');
                  repeat
                    readln(wordcode);
                    if wordcode > 'Z' then 
                      wordcode := chr(ord(wordcode) - changecase)
                  until wordcode in ['H','C','P','?','I'];
                  case wordcode of
                    'H':       kind := hash;
                    'C':       kind := count;
                    'P', ' ':  kind := page;
                    '?':       kind := question;
                    'I':       kind := index
                  end;
                  if kind in [page, question, index] then ref := nil
                end
          end
          else
            writeln('Erroneous word code ', wordcode, ' in file InIndex.')
      end;                           {with statement setting up the node}
      readln(InIndex);          {Advance to the start of the next entry.}
      endlist := eof(InIndex)
    end
  end;                                                {procedure GetNode}


begin                           {procedure BuildTree}
  for lev := -1 to maxheight do  lastnode[lev] := nil;
  counter := 0;
  ch := lastletter[code];
  GetNode(p, ch);
  while p <> nil do
  begin
    counter  := counter + 1;
    Insert(p);
    GetNode(p, ch)
  end;                          {reading and processing input}
  FindRoot;
  ConnectSubtrees
end;                            {procedure  BuildTree}



procedure Process( r: reference);
{Takes the word and page reference r, and updates the binary tree.}
var
  p:          pointer;                      {trace through the tree}
  found:      Boolean;                    {Is the word in the tree?}


procedure UpdateNode( p:  pointer;  r: reference);
{uses reference r to update information in node p^}

var
  q:     pointref;              {used to add reference to list}
begin                                    {procedure UpdateNode}
  with p^ do
  begin
    ct := ct + 1;
    if  kind  in  [page, question, index] then
      if ref = nil then
      begin
        new(ref);
        ref^.pg   := r.pg;
        ref^.next := nil
      end
      else if ref^.pg <> r.pg then
      begin                     {add the new reference to list.}
        new(q);
        q^.pg   := r.pg;
        q^.next := ref;
        ref     := q
      end
  end                           {with statement to update tree}
end;                            {procedure UpdateNode}


procedure NewWord(var p: pointer;  r: reference);
{Creates a node for the first occurrence of a new reference r. A
 pointer to the new node is returned in p.}

var
  response:       char;                {answer received from user}
begin                                          {procedure NewWord}
  new(p);
  with p^ do
  begin
    wd    := r.wd;
    left  := nil;
    right := nil;
    ct    := 1;

    kind  := question;
    repeat                           {ask user what kind of word}
      WriteWord(output, wd);
      write('  is (H, C, P, ?, I)?');
      readln(response);
      if response > 'Z' then response := chr(ord(response) - changecase)
    until response in ['H', 'C', 'P', ' ', '?', 'I'];
    case response of
      'H':         kind := hash;
      'C':         kind := count;
      'P', ' ':    kind := page;
      '?':         begin
                     kind := question;
                     writeln('First occurence of word is on page', r.pg:5, '.')
                   end;
      'I':         kind := index
    end;  {case statement}
    if kind in [page, question, index] then
    begin
      new(ref);
      ref^.pg   := r.pg;
      ref^.next := nil;
    end
  end                                          {with statement}
end;                                        {procedure NewWord}


procedure InsertTree(r, p: pointer);
{adds a node p^ to the tree with root r^; requires that r <> nil
 and p^ not be in the tree; proceeds by recursion}

begin                           {procedure InsertTree}
  if Lt(p^.wd, r^.wd) then
    if r^.left = nil then r^.left := p
    else InsertTree(r^.left, p)
  else
    if r^.right = nil then r^.right := p
    else InsertTree(r^.right, p)
end;                            {procedure InsertTree}


begin                                        {procedure Process}
  if root = nil then                  {The tree might be empty.}
    NewWord(root, r)
  else begin                            {case of non-empty tree}
    p := root;                            {Begin a tree search.}
    found := false;
    repeat
      if r.wd = p^.wd then
        found := true
      else if Lt(r.wd,p^.wd) then
        p := p^.left
      else
        p := p^.right
    until found or (p = nil);

    if found then UpdateNode(p, r)
    else begin                  {p^ was not found: add it to the tree.}
      NewWord(p, r);
      InsertTree(root, p)
    end
  end
end;                                               {procedure Process}


procedure OutputTree( p: pointer);
{traverses the tree for which p^ is the root in inorder}

procedure PutNode( p:  pointer);
{Puts the information in p^ into the file NewIndex.}

var
  q:        pointref;           {used to traverse list of references}
  response: char;
begin                                             {procedure PutNode}
  with p^ do  if ct > 0 then
  begin                         {Otherwise, word is not in document.}
    if kind <> hash then
      WriteWord(NewIndex, wd);
    case kind of
      hash:      begin      {new hash entries written to NewHashFile}
                   WriteWord(NewHashFile, wd);
                   writeln(NewHashFile)
                 end;
      count:     write(NewIndex, 'C');
      page:      write(NewIndex, 'P');
      index:     write(NewIndex, 'I');
      question:
        begin
          repeat                      {ask user what kind of word}
            WriteWord(output, wd);
            write('  is questionable.  Change to (h, c, p, ?, i)?');
            readln(response);
            if response > 'Z' then response := chr(ord(response) - changecase)
          until response in ['H', 'C', 'P',' ', '?', 'I'];
          case response of
            'H':       begin kind := hash;   write(NewIndex, 'H') end;
            'C':       begin kind := count;  write(NewIndex, 'C') end;
            'P', ' ':  begin kind := page;   write(NewIndex, 'P') end;
            'I':       begin kind := index;  write(NewIndex, 'I') end;
            '?':       begin
                         kind := question;
                         write(NewIndex, '?');
                         write('The word appears on the following page(s)');
                         q := ref;
                         repeat
                           write(q^.pg:6);
                           q := q^.next
                         until q = nil;
                         writeln
                       end                  {case of questionable word}
          end                                 {case response statement}
        end                            {treating new or question words}
    end;                                {case kind statement}
    if kind <> hash then
      write(NewIndex, ct:6);
    if kind in [page, question, index] then
    begin
      q := ref;
      RowLength := 28;   {ensures that record will not exceed desired length}
      repeat
        if RowLength > (MaxRowLength - 4) then
          begin
            writeln(NewIndex);
            write(NewIndex,'&  ');     {& indicates continuation of index}
            RowLength := 3
          end;
        write( NewIndex, q^.pg:4);
        q := q^.next;
        RowLength := RowLength + 4
      until q = nil;
    end;
    if kind <> hash then
      writeln( NewIndex )
  end                           {with statement and if statement}
end;                            {procedure PutNode}


begin                                       {procedure OutputTree}
  if p <> nil then
  with p^ do
  begin
    OutputTree(left);                  {Traverse the left subtree}
    PutNode(p);
    OutputTree(right);                {Traverse the right subtree}
    dispose(p)
  end
end;                                        {procedure OutputTree}



begin                           {procedure ClassifyWords}

  write('Name of input word list ?');
  ReadWord(input, inlistname);
  readln;
  open(InIndex, inlistname, readonly);
  reset(InIndex);
  endlist := eof(InIndex);

  write('Name of output word list ?');
  ReadWord(input, newlistname);
  readln;
  open(NewIndex, newlistname);
  rewrite(NewIndex);

  writeln('Rewriting NEWHASHFILE.DAT to contain all new hash words.');
  rewrite(NewHashFile);

  writeln('At the appearance of each word, indicate its disposition:');
  writeln('  H -  Place this word in hash table and count its frequency.');
  writeln('  C -  Count how many times this word appears.');
  writeln('  P -  List pages on which this word appears.');
  writeln('  ? -  Question this word: list pages on which it appears.');
  writeln('  I -  Index this word: list pages on which it appears.');

  for code := 1 to nfiles do      {start main loop through temporary files.}
  begin
    BuildTree(root, code);  {Get the part of master wordlist starting with
               code from the file InIndex, and build it into a binary tree.}
    reset(RefFile[code]);
    for i := 1 to outcount[code] do
    begin
      Process(RefFile[code]^);
                     {use new words from RefFile[code] to update the tree.}
      get( RefFile[code] )
    end;

    OutputTree(root)
                   {write the contents of the tree into file NewIndex.}
  end                                    {main loop on temporary files}
end;                                          {procedure ClassifyWords}

{end of all procedures}



begin                                                    {main program}
  SetTimer;
  SplitWords;                                                 {Phase 1}
  writeln('Time in first phase is ', ElapsedTime:7:1, '   seconds.');
  writeln;

  ClassifyWords;                                              {Phase 2}
  writeln('Time in second phase is', ElapsedTime:7:1, '  seconds.');

  writeln;
  writeln('Processing of input document ', intextname, '  is complete.');
  writeln('Total time in program was ', TotalTime:7:1, '   seconds.')
end.