Diff for /gforth/Attic/gforth.ds between versions 1.15 and 1.18

version 1.15, 1995/04/29 14:51:16 version 1.18, 1995/10/07 17:38:14
Line 2 Line 2
 @comment The source is gforth.ds, from which gforth.texi is generated  @comment The source is gforth.ds, from which gforth.texi is generated
 @comment %**start of header (This is for running Texinfo on a region.)  @comment %**start of header (This is for running Texinfo on a region.)
 @setfilename gforth.info  @setfilename gforth.info
 @settitle GNU Forth Manual  @settitle Gforth Manual
 @comment @setchapternewpage odd  @comment @setchapternewpage odd
 @comment %**end of header (This is for running Texinfo on a region.)  @comment %**end of header (This is for running Texinfo on a region.)
   
 @ifinfo  @ifinfo
 This file documents GNU Forth 0.0  This file documents Gforth 0.1
   
 Copyright @copyright{} 1994 GNU Forth Development Group  Copyright @copyright{} 1994 Gforth Development Group
   
      Permission is granted to make and distribute verbatim copies of       Permission is granted to make and distribute verbatim copies of
      this manual provided the copyright notice and this permission notice       this manual provided the copyright notice and this permission notice
Line 38  Copyright @copyright{} 1994 GNU Forth De Line 38  Copyright @copyright{} 1994 GNU Forth De
   
 @titlepage  @titlepage
 @sp 10  @sp 10
 @center @titlefont{GNU Forth Manual}  @center @titlefont{Gforth Manual}
 @sp 2  @sp 2
 @center for version 0.0  @center for version 0.1
 @sp 2  @sp 2
 @center Anton Ertl  @center Anton Ertl
   @sp 3
   @center This manual is under construction
   
 @comment  The following two commands start the copyright page.  @comment  The following two commands start the copyright page.
 @page  @page
 @vskip 0pt plus 1filll  @vskip 0pt plus 1filll
 Copyright @copyright{} 1994 GNU Forth Development Group  Copyright @copyright{} 1994 Gforth Development Group
   
 @comment !! Published by ... or You can get a copy of this manual ...  @comment !! Published by ... or You can get a copy of this manual ...
   
Line 72  Copyright @copyright{} 1994 GNU Forth De Line 74  Copyright @copyright{} 1994 GNU Forth De
   
 @node Top, License, (dir), (dir)  @node Top, License, (dir), (dir)
 @ifinfo  @ifinfo
 GNU Forth is a free implementation of ANS Forth available on many  Gforth is a free implementation of ANS Forth available on many
 personal machines. This manual corresponds to version 0.0.  personal machines. This manual corresponds to version 0.0.
 @end ifinfo  @end ifinfo
   
 @menu  @menu
 * License::                       * License::                     
 * Goals::                       About the GNU Forth Project  * Goals::                       About the Gforth Project
 * Other Books::                 Things you might want to read  * Other Books::                 Things you might want to read
 * Invocation::                  Starting GNU Forth  * Invocation::                  Starting Gforth
 * Words::                       Forth words available in GNU Forth  * Words::                       Forth words available in Gforth
 * ANS conformance::             Implementation-defined options etc.  * ANS conformance::             Implementation-defined options etc.
 * Model::                       The abstract machine of GNU Forth  * Model::                       The abstract machine of Gforth
 * Emacs and GForth::            The GForth Mode  * Emacs and Gforth::            The Gforth Mode
 * Internals::                   Implementation details  * Internals::                   Implementation details
 * Bugs::                        How to report them  * Bugs::                        How to report them
 * Pedigree::                    Ancestors of GNU Forth  * Pedigree::                    Ancestors of Gforth
 * Word Index::                  An item for each Forth word  * Word Index::                  An item for each Forth word
 * Node Index::                  An item for each node  * Node Index::                  An item for each node
 @end menu  @end menu
Line 98  personal machines. This manual correspon Line 100  personal machines. This manual correspon
   
 @iftex  @iftex
 @unnumbered Preface  @unnumbered Preface
 This manual documents GNU Forth. The reader is expected to know  This manual documents Gforth. The reader is expected to know
 Forth. This manual is primarily a reference manual. @xref{Other Books}  Forth. This manual is primarily a reference manual. @xref{Other Books}
 for introductory material.  for introductory material.
 @end iftex  @end iftex
   
 @node    Goals, Other Books, License, Top  @node    Goals, Other Books, License, Top
 @comment node-name,     next,           previous, up  @comment node-name,     next,           previous, up
 @chapter Goals of GNU Forth  @chapter Goals of Gforth
 @cindex Goals  @cindex Goals
 The goal of the GNU Forth Project is to develop a standard model for  The goal of the Gforth Project is to develop a standard model for
 ANSI Forth. This can be split into several subgoals:  ANSI Forth. This can be split into several subgoals:
   
 @itemize @bullet  @itemize @bullet
 @item  @item
 GNU Forth should conform to the ANSI Forth standard.  Gforth should conform to the ANSI Forth standard.
 @item  @item
 It should be a model, i.e. it should define all the  It should be a model, i.e. it should define all the
 implementation-dependent things.  implementation-dependent things.
Line 121  It should become standard, i.e. widely a Line 123  It should become standard, i.e. widely a
 is the most difficult one.  is the most difficult one.
 @end itemize  @end itemize
   
 To achieve these goals GNU Forth should be  To achieve these goals Gforth should be
 @itemize @bullet  @itemize @bullet
 @item  @item
 Similar to previous models (fig-Forth, F83)  Similar to previous models (fig-Forth, F83)
Line 137  Free. Line 139  Free.
 Available on many machines/easy to port.  Available on many machines/easy to port.
 @end itemize  @end itemize
   
 Have we achieved these goals? GNU Forth conforms to the ANS Forth  Have we achieved these goals? Gforth conforms to the ANS Forth
 standard; it may be considered a model, but we have not yet documented  standard. It may be considered a model, but we have not yet documented
 which parts of the model are stable and which parts we are likely to  which parts of the model are stable and which parts we are likely to
 change; it certainly has not yet become a de facto standard. It has some  change. It certainly has not yet become a de facto standard. It has some
 similarities and some differences to previous models; It has some  similarities and some differences to previous models. It has some
 powerful features, but not yet everything that we envisioned; on RISCs  powerful features, but not yet everything that we envisioned. We
 it is as fast as interpreters programmed in assembly, on  certainly have achieved our execution speed goals (@pxref{Performance}).
 register-starved machines it is not so fast, but still faster than any  It is free and available on many machines.
 other C-based interpretive implementation; it is free and available on  
 many machines.  
   
 @node Other Books, Invocation, Goals, Top  @node Other Books, Invocation, Goals, Top
 @chapter Other books on ANS Forth  @chapter Other books on ANS Forth
   
 As the standard is relatively new, there are not many books out yet. It  As the standard is relatively new, there are not many books out yet. It
 is not recommended to learn Forth by using GNU Forth and a book that is  is not recommended to learn Forth by using Gforth and a book that is
 not written for ANS Forth, as you will not know your mistakes from the  not written for ANS Forth, as you will not know your mistakes from the
 deviations of the book.  deviations of the book.
   
Line 173  other languages should find it ok. Line 173  other languages should find it ok.
 @chapter Invocation  @chapter Invocation
   
 You will usually just say @code{gforth}. In many other cases the default  You will usually just say @code{gforth}. In many other cases the default
 GNU Forth image will be invoked like this:  Gforth image will be invoked like this:
   
 @example  @example
 gforth [files] [-e forth-code]  gforth [files] [-e forth-code]
Line 269  then in @file{~}, then in the normal pat Line 269  then in @file{~}, then in the normal pat
 * Blocks::                        * Blocks::                      
 * Other I/O::                     * Other I/O::                   
 * Programming Tools::             * Programming Tools::           
   * Assembler and Code words::    
 * Threading Words::               * Threading Words::             
 @end menu  @end menu
   
Line 285  that has become a de-facto standard for Line 286  that has become a de-facto standard for
   
 @table @var  @table @var
 @item word  @item word
 The name of the word. BTW, GNU Forth is case insensitive, so you can  The name of the word. BTW, Gforth is case insensitive, so you can
 type the words in in lower case (However, @pxref{core-idef}).  type the words in in lower case (However, @pxref{core-idef}).
   
 @item Stack effect  @item Stack effect
Line 293  The stack effect is written in the notat Line 294  The stack effect is written in the notat
 @var{after}}, where @var{before} and @var{after} describe the top of  @var{after}}, where @var{before} and @var{after} describe the top of
 stack entries before and after the execution of the word. The rest of  stack entries before and after the execution of the word. The rest of
 the stack is not touched by the word. The top of stack is rightmost,  the stack is not touched by the word. The top of stack is rightmost,
 i.e., a stack sequence is written as it is typed in. Note that GNU Forth  i.e., a stack sequence is written as it is typed in. Note that Gforth
 uses a separate floating point stack, but a unified stack  uses a separate floating point stack, but a unified stack
 notation. Also, return stack effects are not shown in @var{stack  notation. Also, return stack effects are not shown in @var{stack
 effect}, but in @var{Description}. The name of a stack item describes  effect}, but in @var{Description}. The name of a stack item describes
Line 409  doc-sm/rem Line 410  doc-sm/rem
   
 @node Double precision, Floating Point, Mixed precision, Arithmetic  @node Double precision, Floating Point, Mixed precision, Arithmetic
 @subsection Double precision  @subsection Double precision
   
   The outer (aka text) interpreter converts numbers containing a dot into
   a double precision number. Note that only numbers with the dot as last
   character are standard-conforming.
   
 doc-d+  doc-d+
 doc-d-  doc-d-
 doc-dnegate  doc-dnegate
Line 419  doc-dmax Line 425  doc-dmax
 @node Floating Point,  , Double precision, Arithmetic  @node Floating Point,  , Double precision, Arithmetic
 @subsection Floating Point  @subsection Floating Point
   
   The format of floating point numbers recognized by the outer (aka text)
   interpreter is: a signed decimal number, possibly containing a decimal
   point (@code{.}), followed by @code{E} or @code{e}, optionally followed
   by a signed integer (the exponent). E.g., @code{1e} ist the same as
   @code{+1.0e+1}. Note that a number without @code{e}
   is not interpreted as floating-point number, but as double (if the
   number contains a @code{.}) or single precision integer. Also,
   conversions between string and floating point numbers always use base
   10, irrespective of the value of @code{BASE}. If @code{BASE} contains a
   value greater then 14, the @code{E} may be interpreted as digit and the
   number will be interpreted as integer, unless it has a signed exponent
   (both @code{+} and @code{-} are allowed as signs).
   
 Angles in floating point operations are given in radians (a full circle  Angles in floating point operations are given in radians (a full circle
 has 2 pi radians). Note, that gforth has a separate floating point  has 2 pi radians). Note, that Gforth has a separate floating point
 stack, but we use the unified notation.  stack, but we use the unified notation.
   
 Floating point numbers have a number of unpleasant surprises for the  Floating point numbers have a number of unpleasant surprises for the
Line 468  doc-fatanh Line 487  doc-fatanh
 @node Stack Manipulation, Memory access, Arithmetic, Words  @node Stack Manipulation, Memory access, Arithmetic, Words
 @section Stack Manipulation  @section Stack Manipulation
   
 gforth has a data stack (aka parameter stack) for characters, cells,  Gforth has a data stack (aka parameter stack) for characters, cells,
 addresses, and double cells, a floating point stack for floating point  addresses, and double cells, a floating point stack for floating point
 numbers, a return stack for storing the return addresses of colon  numbers, a return stack for storing the return addresses of colon
 definitions and other data, and a locals stack for storing local  definitions and other data, and a locals stack for storing local
Line 594  must only occur at specific addresses; e Line 613  must only occur at specific addresses; e
 accessed at addresses divisible by 4. Even if a machine allows unaligned  accessed at addresses divisible by 4. Even if a machine allows unaligned
 accesses, it can usually perform aligned accesses faster.   accesses, it can usually perform aligned accesses faster. 
   
 For the performance-concious: alignment operations are usually only  For the performance-conscious: alignment operations are usually only
 necessary during the definition of a data structure, not during the  necessary during the definition of a data structure, not during the
 (more frequent) accesses to it.  (more frequent) accesses to it.
   
Line 604  char-aligned have no use in the standard Line 623  char-aligned have no use in the standard
 created.  created.
   
 The standard guarantees that addresses returned by @code{CREATE}d words  The standard guarantees that addresses returned by @code{CREATE}d words
 are cell-aligned; in addition, gforth guarantees that these addresses  are cell-aligned; in addition, Gforth guarantees that these addresses
 are aligned for all purposes.  are aligned for all purposes.
   
 Note that the standard defines a word @code{char}, which has nothing to  Note that the standard defines a word @code{char}, which has nothing to
Line 790  There are several variations on the coun Line 809  There are several variations on the coun
   
 @code{LEAVE} leaves the innermost counted loop immediately.  @code{LEAVE} leaves the innermost counted loop immediately.
   
   If @var{start} is greater than @var{limit}, a @code{?DO} loop is entered
   (and @code{LOOP} iterates until they become equal by wrap-around
   arithmetic). This behaviour is usually not what you want. Therefore,
   Gforth offers @code{+DO} and @code{U+DO} (as replacements for
   @code{?DO}), which do not enter the loop if @var{start} is greater than
   @var{limit}; @code{+DO} is for signed loop parameters, @code{U+DO} for
   unsigned loop parameters. These words can be implemented easily on
   standard systems, so using them does not make your programs hard to
   port; e.g.:
   @example
   : +DO ( compile-time: -- do-sys; run-time: n1 n2 -- )
       POSTPONE over POSTPONE min POSTPONE ?DO ; immediate
   @end example
   
 @code{LOOP} can be replaced with @code{@var{n} +LOOP}; this updates the  @code{LOOP} can be replaced with @code{@var{n} +LOOP}; this updates the
 index by @var{n} instead of by 1. The loop is terminated when the border  index by @var{n} instead of by 1. The loop is terminated when the border
 between @var{limit-1} and @var{limit} is crossed. E.g.:  between @var{limit-1} and @var{limit} is crossed. E.g.:
   
 @code{4 0 ?DO  i .  2 +LOOP}   prints @code{0 2}  @code{4 0 +DO  i .  2 +LOOP}   prints @code{0 2}
   
 @code{4 1 ?DO  i .  2 +LOOP}   prints @code{1 3}  @code{4 1 +DO  i .  2 +LOOP}   prints @code{1 3}
   
 The behaviour of @code{@var{n} +LOOP} is peculiar when @var{n} is negative:  The behaviour of @code{@var{n} +LOOP} is peculiar when @var{n} is negative:
   
Line 804  The behaviour of @code{@var{n} +LOOP} is Line 837  The behaviour of @code{@var{n} +LOOP} is
   
 @code{ 0 0 ?DO  i .  -1 +LOOP}  prints nothing  @code{ 0 0 ?DO  i .  -1 +LOOP}  prints nothing
   
 Therefore we recommend avoiding using @code{@var{n} +LOOP} with negative  Therefore we recommend avoiding @code{@var{n} +LOOP} with negative
 @var{n}. One alternative is @code{@var{n} S+LOOP}, where the negative  @var{n}. One alternative is @code{@var{u} -LOOP}, which reduces the
 case behaves symmetrical to the positive case:  index by @var{u} each iteration. The loop is terminated when the border
   between @var{limit+1} and @var{limit} is crossed. Gforth also provides
   @code{-DO} and @code{U-DO} for down-counting loops. E.g.:
   
 @code{-2 0 ?DO  i .  -1 S+LOOP}  prints @code{0 -1}  @code{-2 0 -DO  i .  1 -LOOP}  prints @code{0 -1}
   
 @code{-1 0 ?DO  i .  -1 S+LOOP}  prints @code{0}  @code{-1 0 -DO  i .  1 -LOOP}  prints @code{0}
   
 @code{ 0 0 ?DO  i .  -1 S+LOOP}  prints nothing  @code{ 0 0 -DO  i .  1 -LOOP}  prints nothing
   
 The loop is terminated when the border between @var{limit@minus{}sgn(n)} and  Another alternative is @code{@var{n} S+LOOP}, where the negative
 @var{limit} is crossed. However, @code{S+LOOP} is not part of the ANS  case behaves symmetrical to the positive case:
 Forth standard.  
   
 @code{?DO} can be replaced by @code{DO}. @code{DO} enters the loop even  @code{-2 0 -DO  i .  -1 S+LOOP}  prints @code{0 -1}
 when the start and the limit value are equal. We do not recommend using  
 @code{DO}. It will just give you maintenance troubles.  The loop is terminated when the border between @var{limit@minus{}sgn(n)}
   and @var{limit} is crossed. Unfortunately, neither @code{-LOOP} nor
   @code{S+LOOP} are part of the ANS Forth standard, and they are not easy
   to implement using standard words. If you want to write standard
   programs, just avoid counting down.
   
   @code{?DO} can also be replaced by @code{DO}. @code{DO} always enters
   the loop, independent of the loop parameters. Do not use @code{DO}, even
   if you know that the loop is entered in any case. Such knowledge tends
   to become invalid during maintenance of a program, and then the
   @code{DO} will make trouble.
   
 @code{UNLOOP} is used to prepare for an abnormal loop exit, e.g., via  @code{UNLOOP} is used to prepare for an abnormal loop exit, e.g., via
 @code{EXIT}. @code{UNLOOP} removes the loop control parameters from the  @code{EXIT}. @code{UNLOOP} removes the loop control parameters from the
Line 834  FOR Line 878  FOR
 NEXT  NEXT
 @end example  @end example
 This is the preferred loop of native code compiler writers who are too  This is the preferred loop of native code compiler writers who are too
 lazy to optimize @code{?DO} loops properly. In GNU Forth, this loop  lazy to optimize @code{?DO} loops properly. In Gforth, this loop
 iterates @var{n+1} times; @code{i} produces values starting with @var{n}  iterates @var{n+1} times; @code{i} produces values starting with @var{n}
 and ending with 0. Other Forth systems may behave differently, even if  and ending with 0. Other Forth systems may behave differently, even if
 they support @code{FOR} loops.  they support @code{FOR} loops.
Line 845  they support @code{FOR} loops. Line 889  they support @code{FOR} loops.
 ANS Forth permits and supports using control structures in a non-nested  ANS Forth permits and supports using control structures in a non-nested
 way. Information about incomplete control structures is stored on the  way. Information about incomplete control structures is stored on the
 control-flow stack. This stack may be implemented on the Forth data  control-flow stack. This stack may be implemented on the Forth data
 stack, and this is what we have done in gforth.  stack, and this is what we have done in Gforth.
   
 An @i{orig} entry represents an unresolved forward branch, a @i{dest}  An @i{orig} entry represents an unresolved forward branch, a @i{dest}
 entry represents a backward branch target. A few words are the basis for  entry represents a backward branch target. A few words are the basis for
Line 861  doc-again Line 905  doc-again
 doc-cs-pick  doc-cs-pick
 doc-cs-roll  doc-cs-roll
   
 On many systems control-flow stack items take one word, in gforth they  On many systems control-flow stack items take one word, in Gforth they
 currently take three (this may change in the future). Therefore it is a  currently take three (this may change in the future). Therefore it is a
 really good idea to manipulate the control flow stack with  really good idea to manipulate the control flow stack with
 @code{cs-pick} and @code{cs-roll}, not with data stack manipulation  @code{cs-pick} and @code{cs-roll}, not with data stack manipulation
Line 876  doc-repeat Line 920  doc-repeat
 Counted loop words constitute a separate group of words:  Counted loop words constitute a separate group of words:
   
 doc-?do  doc-?do
   doc-+do
   doc-u+do
   doc--do
   doc-u-do
 doc-do  doc-do
 doc-for  doc-for
 doc-loop  doc-loop
 doc-s+loop  doc-s+loop
 doc-+loop  doc-+loop
   doc--loop
 doc-next  doc-next
 doc-leave  doc-leave
 doc-?leave  doc-?leave
Line 951  necessary to define them. Line 1000  necessary to define them.
 @subsection Calls and returns  @subsection Calls and returns
   
 A definition can be called simply be writing the name of the  A definition can be called simply be writing the name of the
 definition. When the end of the definition is reached, it returns. An earlier return can be forced using  definition. When the end of the definition is reached, it returns. An
   earlier return can be forced using
   
 doc-exit  doc-exit
   
Line 977  locals wordset, but also our own, more p Line 1027  locals wordset, but also our own, more p
 implemented the ANS Forth locals wordset through our locals wordset).  implemented the ANS Forth locals wordset through our locals wordset).
   
 @menu  @menu
 * gforth locals::                 * Gforth locals::               
 * ANS Forth locals::              * ANS Forth locals::            
 @end menu  @end menu
   
 @node gforth locals, ANS Forth locals, Locals, Locals  @node Gforth locals, ANS Forth locals, Locals, Locals
 @subsection gforth locals  @subsection Gforth locals
   
 Locals can be defined with  Locals can be defined with
   
Line 1025  The name of the local may be preceded by Line 1075  The name of the local may be preceded by
  Ar Bi f* Ai Br f* f+ ;   Ar Bi f* Ai Br f* f+ ;
 @end example  @end example
   
 GNU Forth currently supports cells (@code{W:}, @code{W^}), doubles  Gforth currently supports cells (@code{W:}, @code{W^}), doubles
 (@code{D:}, @code{D^}), floats (@code{F:}, @code{F^}) and characters  (@code{D:}, @code{D^}), floats (@code{F:}, @code{F^}) and characters
 (@code{C:}, @code{C^}) in two flavours: a value-flavoured local (defined  (@code{C:}, @code{C^}) in two flavours: a value-flavoured local (defined
 with @code{W:}, @code{D:} etc.) produces its value and can be changed  with @code{W:}, @code{D:} etc.) produces its value and can be changed
Line 1045  locals are initialized with values from Line 1095  locals are initialized with values from
 Currently there is no way to define locals with user-defined data  Currently there is no way to define locals with user-defined data
 structures, but we are working on it.  structures, but we are working on it.
   
 GNU Forth allows defining locals everywhere in a colon definition. This  Gforth allows defining locals everywhere in a colon definition. This
 poses the following questions:  poses the following questions:
   
 @menu  @menu
Line 1055  poses the following questions: Line 1105  poses the following questions:
 * Implementation::                * Implementation::              
 @end menu  @end menu
   
 @node Where are locals visible by name?, How long do locals live?, gforth locals, gforth locals  @node Where are locals visible by name?, How long do locals live?, Gforth locals, Gforth locals
 @subsubsection Where are locals visible by name?  @subsubsection Where are locals visible by name?
   
 Basically, the answer is that locals are visible where you would expect  Basically, the answer is that locals are visible where you would expect
Line 1177  If the @code{BEGIN} is not reachable fro Line 1227  If the @code{BEGIN} is not reachable fro
 @code{AHEAD} or @code{EXIT}), the compiler cannot even make an  @code{AHEAD} or @code{EXIT}), the compiler cannot even make an
 optimistic guess, as the locals visible after the @code{BEGIN} may be  optimistic guess, as the locals visible after the @code{BEGIN} may be
 defined later. Therefore, the compiler assumes that no locals are  defined later. Therefore, the compiler assumes that no locals are
 visible after the @code{BEGIN}. However, the useer can use  visible after the @code{BEGIN}. However, the user can use
 @code{ASSUME-LIVE} to make the compiler assume that the same locals are  @code{ASSUME-LIVE} to make the compiler assume that the same locals are
 visible at the BEGIN as at the point where the item was created.  visible at the BEGIN as at the point where the top control-flow stack
   item was created.
   
 doc-assume-live  doc-assume-live
   
Line 1213  WHILE Line 1264  WHILE
 REPEAT  REPEAT
 @end example  @end example
   
 @node How long do locals live?, Programming Style, Where are locals visible by name?, gforth locals  @node How long do locals live?, Programming Style, Where are locals visible by name?, Gforth locals
 @subsubsection How long do locals live?  @subsubsection How long do locals live?
   
 The right answer for the lifetime question would be: A local lives at  The right answer for the lifetime question would be: A local lives at
Line 1227  languages (e.g., C): The local lives onl Line 1278  languages (e.g., C): The local lives onl
 afterwards its address is invalid (and programs that access it  afterwards its address is invalid (and programs that access it
 afterwards are erroneous).  afterwards are erroneous).
   
 @node Programming Style, Implementation, How long do locals live?, gforth locals  @node Programming Style, Implementation, How long do locals live?, Gforth locals
 @subsubsection Programming Style  @subsubsection Programming Style
   
 The freedom to define locals anywhere has the potential to change  The freedom to define locals anywhere has the potential to change
Line 1241  write the items in the order you want. Line 1292  write the items in the order you want.
 This seems a little far-fetched and eliminating stack manipulations is  This seems a little far-fetched and eliminating stack manipulations is
 unlikely to become a conscious programming objective. Still, the number  unlikely to become a conscious programming objective. Still, the number
 of stack manipulations will be reduced dramatically if local variables  of stack manipulations will be reduced dramatically if local variables
 are used liberally (e.g., compare @code{max} in @ref{gforth locals} with  are used liberally (e.g., compare @code{max} in @ref{Gforth locals} with
 a traditional implementation of @code{max}).  a traditional implementation of @code{max}).
   
 This shows one potential benefit of locals: making Forth programs more  This shows one potential benefit of locals: making Forth programs more
Line 1296  are initialized with the right value for Line 1347  are initialized with the right value for
 Here it is clear from the start that @code{s1} has a different value  Here it is clear from the start that @code{s1} has a different value
 in every loop iteration.  in every loop iteration.
   
 @node Implementation,  , Programming Style, gforth locals  @node Implementation,  , Programming Style, Gforth locals
 @subsubsection Implementation  @subsubsection Implementation
   
 GNU Forth uses an extra locals stack. The most compelling reason for  Gforth uses an extra locals stack. The most compelling reason for
 this is that the return stack is not float-aligned; using an extra stack  this is that the return stack is not float-aligned; using an extra stack
 also eliminates the problems and restrictions of using the return stack  also eliminates the problems and restrictions of using the return stack
 as locals stack. Like the other stacks, the locals stack grows toward  as locals stack. Like the other stacks, the locals stack grows toward
Line 1334  area and @code{@}} switches it back and Line 1385  area and @code{@}} switches it back and
 initializing code. @code{W:} etc.@ are normal defining words. This  initializing code. @code{W:} etc.@ are normal defining words. This
 special area is cleared at the start of every colon definition.  special area is cleared at the start of every colon definition.
   
 A special feature of GNU Forths dictionary is used to implement the  A special feature of Gforth's dictionary is used to implement the
 definition of locals without type specifiers: every wordlist (aka  definition of locals without type specifiers: every wordlist (aka
 vocabulary) has its own methods for searching  vocabulary) has its own methods for searching
 etc. (@pxref{Wordlists}). For the present purpose we defined a wordlist  etc. (@pxref{Wordlists}). For the present purpose we defined a wordlist
Line 1424  this may lead to increased space needs f Line 1475  this may lead to increased space needs f
 usually less than reclaiming this space would cost in code size.  usually less than reclaiming this space would cost in code size.
   
   
 @node ANS Forth locals,  , gforth locals, Locals  @node ANS Forth locals,  , Gforth locals, Locals
 @subsection ANS Forth locals  @subsection ANS Forth locals
   
 The ANS Forth locals wordset does not define a syntax for locals, but  The ANS Forth locals wordset does not define a syntax for locals, but
 words that make it possible to define various syntaxes. One of the  words that make it possible to define various syntaxes. One of the
 possible syntaxes is a subset of the syntax we used in the gforth locals  possible syntaxes is a subset of the syntax we used in the Gforth locals
 wordset, i.e.:  wordset, i.e.:
   
 @example  @example
Line 1445  restrictions are: Line 1496  restrictions are:
   
 @itemize @bullet  @itemize @bullet
 @item  @item
 Locals can only be cell-sized values (no type specifers are allowed).  Locals can only be cell-sized values (no type specifiers are allowed).
 @item  @item
 Locals can be defined only outside control structures.  Locals can be defined only outside control structures.
 @item  @item
 Locals can interfere with explicit usage of the return stack. For the  Locals can interfere with explicit usage of the return stack. For the
 exact (and long) rules, see the standard. If you don't use return stack  exact (and long) rules, see the standard. If you don't use return stack
 accessing words in a definition using locals, you will we all right. The  accessing words in a definition using locals, you will be all right. The
 purpose of this rule is to make locals implementation on the return  purpose of this rule is to make locals implementation on the return
 stack easier.  stack easier.
 @item  @item
Line 1462  Locals defined in this way behave like @ Line 1513  Locals defined in this way behave like @
 (@xref{Values}). I.e., they are initialized from the stack. Using their  (@xref{Values}). I.e., they are initialized from the stack. Using their
 name produces their value. Their value can be changed using @code{TO}.  name produces their value. Their value can be changed using @code{TO}.
   
 Since this syntax is supported by gforth directly, you need not do  Since this syntax is supported by Gforth directly, you need not do
 anything to use it. If you want to port a program using this syntax to  anything to use it. If you want to port a program using this syntax to
 another ANS Forth system, use @file{anslocal.fs} to implement the syntax  another ANS Forth system, use @file{anslocal.fs} to implement the syntax
 on the other system.  on the other system.
Line 1477  doc-(local) Line 1528  doc-(local)
   
 The ANS Forth locals extension wordset defines a syntax, but it is so  The ANS Forth locals extension wordset defines a syntax, but it is so
 awful that we strongly recommend not to use it. We have implemented this  awful that we strongly recommend not to use it. We have implemented this
 syntax to make porting to gforth easy, but do not document it here. The  syntax to make porting to Gforth easy, but do not document it here. The
 problem with this syntax is that the locals are defined in an order  problem with this syntax is that the locals are defined in an order
 reversed with respect to the standard stack comment notation, making  reversed with respect to the standard stack comment notation, making
 programs harder to read, and easier to misread and miswrite. The only  programs harder to read, and easier to misread and miswrite. The only
Line 1506  locals wordset. Line 1557  locals wordset.
 @node Other I/O, Programming Tools, Blocks, Words  @node Other I/O, Programming Tools, Blocks, Words
 @section Other I/O  @section Other I/O
   
 @node Programming Tools, Threading Words, Other I/O, Words  @node Programming Tools, Assembler and Code words, Other I/O, Words
 @section Programming Tools  @section Programming Tools
   
 @menu  @menu
Line 1551  doc-printdebugline Line 1602  doc-printdebugline
   
 It is a good idea to make your programs self-checking, in particular, if  It is a good idea to make your programs self-checking, in particular, if
 you use an assumption (e.g., that a certain field of a data structure is  you use an assumption (e.g., that a certain field of a data structure is
 never zero) that may become wrong during maintenance. GForth supports  never zero) that may become wrong during maintenance. Gforth supports
 assertions for this purpose. They are used like this:  assertions for this purpose. They are used like this:
   
 @example  @example
Line 1574  debugging, we want more checking, in pro Line 1625  debugging, we want more checking, in pro
 for speed. Therefore, assertions can be turned off, i.e., the assertion  for speed. Therefore, assertions can be turned off, i.e., the assertion
 becomes a comment. Depending on the importance of an assertion and the  becomes a comment. Depending on the importance of an assertion and the
 time it takes to check it, you may want to turn off some assertions and  time it takes to check it, you may want to turn off some assertions and
 keep others turned on. GForth provides several levels of assertions for  keep others turned on. Gforth provides several levels of assertions for
 this purpose:  this purpose:
   
 doc-assert0(  doc-assert0(
Line 1605  If there is interest, we will introduce Line 1656  If there is interest, we will introduce
 intend to @code{catch} a specific condition, using @code{throw} is  intend to @code{catch} a specific condition, using @code{throw} is
 probably more appropriate than an assertion).  probably more appropriate than an assertion).
   
 @node Threading Words,  , Programming Tools, Words  @node Assembler and Code words, Threading Words, Programming Tools, Words
   @section Assembler and Code words
   
   Gforth provides some words for defining primitives (words written in
   machine code), and for defining the the machine-code equivalent of
   @code{DOES>}-based defining words. However, the machine-independent
   nature of Gforth poses a few problems: First of all. Gforth runs on
   several architectures, so it can provide no standard assembler. What's
   worse is that the register allocation not only depends on the processor,
   but also on the gcc version and options used.
   
   The words Gforth offers encapsulate some system dependences (e.g., the
   header structure), so a system-independent assembler may be used in
   Gforth. If you do not have an assembler, you can compile machine code
   directly with @code{,} and @code{c,}.
   
   doc-assembler
   doc-code
   doc-end-code
   doc-;code
   doc-flush-icache
   
   If @code{flush-icache} does not work correctly, @code{code} words
   etc. will not work (reliably), either.
   
   These words are rarely used. Therefore they reside in @code{code.fs},
   which is usually not loaded (except @code{flush-icache}, which is always
   present). You can load it with @code{require code.fs}.
   
   Another option for implementing normal and defining words efficiently
   is: adding the wanted functionality to the source of Gforth. For normal
   words you just have to edit @file{primitives}, defining words (for fast
   defined words) probably require changes in @file{engine.c},
   @file{kernal.fs}, @file{prims2x.fs}, and possibly @file{cross.fs}.
   
   
   @node Threading Words,  , Assembler and Code words, Words
 @section Threading Words  @section Threading Words
   
 These words provide access to code addresses and other threading stuff  These words provide access to code addresses and other threading stuff
 in gforth (and, possibly, other interpretive Forths). It more or less  in Gforth (and, possibly, other interpretive Forths). It more or less
 abstracts away the differences between direct and indirect threading  abstracts away the differences between direct and indirect threading
 (and, for direct threading, the machine dependences). However, at  (and, for direct threading, the machine dependences). However, at
 present this wordset is still inclomplete. It is also pretty low-level;  present this wordset is still inclomplete. It is also pretty low-level;
Line 1623  doc-does-code! Line 1710  doc-does-code!
 doc-does-handler!  doc-does-handler!
 doc-/does-handler  doc-/does-handler
   
   The code addresses produced by various defining words are produced by
   the following words:
   
   doc-docol:
   doc-docon:
   doc-dovar:
   doc-douser:
   doc-dodefer:
   doc-dofield:
   
   Currently there is no installation-independent way for recogizing words
   defined by a @code{CREATE}...@code{DOES>} word; however, once you know
   that a word is defined by a @code{CREATE}...@code{DOES>} word, you can
   use @code{>DOES-CODE}.
   
 @node ANS conformance, Model, Words, Top  @node ANS conformance, Model, Words, Top
 @chapter ANS conformance  @chapter ANS conformance
   
 To the best of our knowledge, gforth is an  To the best of our knowledge, Gforth is an
   
 ANS Forth System  ANS Forth System
 @itemize  @itemize
Line 1650  ANS Forth System Line 1750  ANS Forth System
 @item providing the Memory-Allocation word set  @item providing the Memory-Allocation word set
 @item providing the Memory-Allocation Extensions word set (that one's easy)  @item providing the Memory-Allocation Extensions word set (that one's easy)
 @item providing the Programming-Tools word set  @item providing the Programming-Tools word set
 @item providing @code{AHEAD}, @code{BYE}, @code{CS-PICK}, @code{CS-ROLL}, @code{STATE}, @code{[ELSE]}, @code{[IF]}, @code{[THEN]} from the Programming-Tools Extensions word set  @item providing @code{;code}, @code{AHEAD}, @code{ASSEMBLER}, @code{BYE}, @code{CODE}, @code{CS-PICK}, @code{CS-ROLL}, @code{STATE}, @code{[ELSE]}, @code{[IF]}, @code{[THEN]} from the Programming-Tools Extensions word set
 @item providing the Search-Order word set  @item providing the Search-Order word set
 @item providing the Search-Order Extensions word set  @item providing the Search-Order Extensions word set
 @item providing the String word set  @item providing the String word set
Line 1663  requirements. In many cases it gives a w Line 1763  requirements. In many cases it gives a w
 information instead of providing the information directly, in  information instead of providing the information directly, in
 particular, if the information depends on the processor, the operating  particular, if the information depends on the processor, the operating
 system or the installation options chosen, or if they are likely to  system or the installation options chosen, or if they are likely to
 change during the maintenance of gforth.  change during the maintenance of Gforth.
   
 @comment The framework for the rest has been taken from pfe.  @comment The framework for the rest has been taken from pfe.
   
Line 1702  change during the maintenance of gforth. Line 1802  change during the maintenance of gforth.
 @table @i  @table @i
   
 @item (Cell) aligned addresses:  @item (Cell) aligned addresses:
 processor-dependent. Gforths alignment words perform natural alignment  processor-dependent. Gforth's alignment words perform natural alignment
 (e.g., an address aligned for a datum of size 8 is divisible by  (e.g., an address aligned for a datum of size 8 is divisible by
 8). Unaligned accesses usually result in a @code{-23 THROW}.  8). Unaligned accesses usually result in a @code{-23 THROW}.
   
Line 1727  installation-dependent. Currently a char Line 1827  installation-dependent. Currently a char
 (Comments on that requested).  (Comments on that requested).
   
 @item character-set extensions and matching of names:  @item character-set extensions and matching of names:
 Any character except 0 can be used in a name. Matching is  Any character except the ASCII NUL charcter can be used in a
 case-insensitive. The matching is performed using the C function  name. Matching is case-insensitive. The matching is performed using the
 @code{strncasecmp}, whose function is probably influenced by the  C function @code{strncasecmp}, whose function is probably influenced by
 locale. E.g., the @code{C} locale does not know about accents and  the locale. E.g., the @code{C} locale does not know about accents and
 umlauts, so they are matched case-sensitively in that locale. For  umlauts, so they are matched case-sensitively in that locale. For
 portability reasons it is best to write programs such that they work in  portability reasons it is best to write programs such that they work in
 the @code{C} locale. Then one can use libraries written by a Polish  the @code{C} locale. Then one can use libraries written by a Polish
Line 1790  Given by the constant @code{/line}. Curr Line 1890  Given by the constant @code{/line}. Curr
 31  31
   
 @item method of selecting the user input device:  @item method of selecting the user input device:
 The user input device is the standard input. There is current no way to  The user input device is the standard input. There is currently no way to
 change it from within gforth. However, the input can typically be  change it from within Gforth. However, the input can typically be
 redirected in the command line that starts gforth.  redirected in the command line that starts Gforth.
   
 @item method of selecting the user output device:  @item method of selecting the user output device:
 The user output device is the standard output. It cannot be redirected  The user output device is the standard output. It cannot be redirected
 from within gforth, but typically from the command line that starts  from within Gforth, but typically from the command line that starts
 gforth. Gforth uses buffered output, so output on a terminal does not  Gforth. Gforth uses buffered output, so output on a terminal does not
 become visible before the next newline or buffer overflow. Output on  become visible before the next newline or buffer overflow. Output on
 non-terminals is invisible until the buffer overflows.  non-terminals is invisible until the buffer overflows.
   
 @item methods of dictionary compilation:  @item methods of dictionary compilation:
 Waht are we expected to document here?  What are we expected to document here?
   
 @item number of bits in one address unit:  @item number of bits in one address unit:
 @code{s" address-units-bits" environment? drop .}. 8 in all current  @code{s" address-units-bits" environment? drop .}. 8 in all current
Line 1838  string. Line 1938  string.
 Varies. You can determine the size at a specific time using @code{lp@  Varies. You can determine the size at a specific time using @code{lp@
 tib - .}. It is shared with the locals stack and TIBs of files that  tib - .}. It is shared with the locals stack and TIBs of files that
 include the current file. You can change the amount of space for TIBs  include the current file. You can change the amount of space for TIBs
 and locals stack at gforth startup with the command line option  and locals stack at Gforth startup with the command line option
 @code{-l}.  @code{-l}.
   
 @item size of the pictured numeric output buffer:  @item size of the pictured numeric output buffer:
Line 2216  another question. Line 2316  another question.
   
 @item repeatability to be expected from the execution of @code{MS}:  @item repeatability to be expected from the execution of @code{MS}:
 System dependent. On Unix, a lot depends on load. If the system is  System dependent. On Unix, a lot depends on load. If the system is
 lightly loaded, and the delay is short enough that gforth does not get  lightly loaded, and the delay is short enough that Gforth does not get
 swapped out, the performance should be acceptable. Under MS-DOS and  swapped out, the performance should be acceptable. Under MS-DOS and
 other single-tasking systems, it should be good.  other single-tasking systems, it should be good.
   
Line 2647  when @code{REVEAL} is executed (by @code Line 2747  when @code{REVEAL} is executed (by @code
 @end table  @end table
   
   
 @node Model, Emacs and GForth, ANS conformance, Top  @node Model, Emacs and Gforth, ANS conformance, Top
 @chapter Model  @chapter Model
   
 @node Emacs and GForth, Internals, Model, Top  @node Emacs and Gforth, Internals, Model, Top
 @chapter Emacs and GForth  @chapter Emacs and Gforth
   
 GForth comes with @file{gforth.el}, an improved version of  Gforth comes with @file{gforth.el}, an improved version of
 @file{forth.el} by Goran Rydqvist (icluded in the TILE package). The  @file{forth.el} by Goran Rydqvist (icluded in the TILE package). The
 improvements are a better (but still not perfect) handling of  improvements are a better (but still not perfect) handling of
 indentation. I have also added comment paragraph filling (@kbd{M-q}),  indentation. I have also added comment paragraph filling (@kbd{M-q}),
Line 2663  stuff I do not use alone, even though so Line 2763  stuff I do not use alone, even though so
 TILE. To get a description of these features, enter Forth mode and type  TILE. To get a description of these features, enter Forth mode and type
 @kbd{C-h m}.  @kbd{C-h m}.
   
 In addition, GForth supports Emacs quite well: The source code locations  In addition, Gforth supports Emacs quite well: The source code locations
 given in error messages, debugging output (from @code{~~}) and failed  given in error messages, debugging output (from @code{~~}) and failed
 assertion messages are in the right format for Emacs' compilation mode  assertion messages are in the right format for Emacs' compilation mode
 (@pxref{Compilation, , Running Compilations under Emacs, emacs, Emacs  (@pxref{Compilation, , Running Compilations under Emacs, emacs, Emacs
Line 2675  Also, if you @code{include} @file{etags. Line 2775  Also, if you @code{include} @file{etags.
 (@pxref{Tags, , Tags Tables, emacs, Emacs Manual}) will be produced that  (@pxref{Tags, , Tags Tables, emacs, Emacs Manual}) will be produced that
 contains the definitions of all words defined afterwards. You can then  contains the definitions of all words defined afterwards. You can then
 find the source for a word using @kbd{M-.}. Note that emacs can use  find the source for a word using @kbd{M-.}. Note that emacs can use
 several tags files at the same time (e.g., one for the gforth sources  several tags files at the same time (e.g., one for the Gforth sources
 and one for your program).  and one for your program).
   
 To get all these benefits, add the following lines to your @file{.emacs}  To get all these benefits, add the following lines to your @file{.emacs}
Line 2686  file: Line 2786  file:
 (setq auto-mode-alist (cons '("\\.fs\\'" . forth-mode) auto-mode-alist))  (setq auto-mode-alist (cons '("\\.fs\\'" . forth-mode) auto-mode-alist))
 @end example  @end example
   
 @node Internals, Bugs, Emacs and GForth, Top  @node Internals, Bugs, Emacs and Gforth, Top
 @chapter Internals  @chapter Internals
   
 Reading this section is not necessary for programming with gforth. It  Reading this section is not necessary for programming with Gforth. It
 should be helpful for finding your way in the gforth sources.  should be helpful for finding your way in the Gforth sources.
   
 @menu  @menu
 * Portability::                   * Portability::                 
 * Threading::                     * Threading::                   
 * Primitives::                    * Primitives::                  
 * System Architecture::           * System Architecture::         
   * Performance::                 
 @end menu  @end menu
   
 @node Portability, Threading, Internals, Internals  @node Portability, Threading, Internals, Internals
Line 2728  Double-Word Integers, gcc.info, GNU C Ma Line 2829  Double-Word Integers, gcc.info, GNU C Ma
 double numbers. GNU C is available for free on all important (and many  double numbers. GNU C is available for free on all important (and many
 unimportant) UNIX machines, VMS, 80386s running MS-DOS, the Amiga, and  unimportant) UNIX machines, VMS, 80386s running MS-DOS, the Amiga, and
 the Atari ST, so a Forth written in GNU C can run on all these  the Atari ST, so a Forth written in GNU C can run on all these
 machines@footnote{Due to Apple's look-and-feel lawsuit it is not  machines.
 available on the Mac (@pxref{Boycott, , Protect Your Freedom---Fight  
 ``Look And Feel'', gcc.info, GNU C Manual}).}.  
   
 Writing in a portable language has the reputation of producing code that  Writing in a portable language has the reputation of producing code that
 is slower than assembly. For our Forth engine we repeatedly looked at  is slower than assembly. For our Forth engine we repeatedly looked at
Line 3021  To see what assembly code is produced fo Line 3120  To see what assembly code is produced fo
 with your compiler and your flag settings, type @code{make engine.s} and  with your compiler and your flag settings, type @code{make engine.s} and
 look at the resulting file @file{engine.s}.  look at the resulting file @file{engine.s}.
   
 @node System Architecture,  , Primitives, Internals  @node System Architecture, Performance, Primitives, Internals
 @section System Architecture  @section System Architecture
   
 Our Forth system consists not only of primitives, but also of  Our Forth system consists not only of primitives, but also of
Line 3044  possible, because we do not want to dist Line 3143  possible, because we do not want to dist
 same image file, and to make it easy for the users to use their image  same image file, and to make it easy for the users to use their image
 files on many machines. We currently need to create a different image  files on many machines. We currently need to create a different image
 file for machines with different cell sizes and different byte order  file for machines with different cell sizes and different byte order
 (little- or big-endian)@footnote{We consider adding information to the  (little- or big-endian)@footnote{We are considering adding information to the
 image file that enables the loader to change the byte order.}.  image file that enables the loader to change the byte order.}.
   
 Forth code that is going to end up in a portable image file has to  Forth code that is going to end up in a portable image file has to
Line 3064  at run-time. The loader also has to repl Line 3163  at run-time. The loader also has to repl
 primitive calls with the appropriate code-field addresses (or code  primitive calls with the appropriate code-field addresses (or code
 addresses in the case of direct threading).  addresses in the case of direct threading).
   
   @node  Performance,  , System Architecture, Internals
   @section Performance
   
   On RISCs the Gforth engine is very close to optimal; i.e., it is usually
   impossible to write a significantly faster engine.
   
   On register-starved machines like the 386 architecture processors
   improvements are possible, because @code{gcc} does not utilize the
   registers as well as a human, even with explicit register declarations;
   e.g., Bernd Beuster wrote a Forth system fragment in assembly language
   and hand-tuned it for the 486; this system is 1.19 times faster on the
   Sieve benchmark on a 486DX2/66 than Gforth compiled with
   @code{gcc-2.6.3} with @code{-DFORCE_REG}.
   
   However, this potential advantage of assembly language implementations
   is not necessarily realized in complete Forth systems: We compared
   Gforth (compiled with @code{gcc-2.6.3} and @code{-DFORCE_REG}) with
   Win32Forth 1.2093 and LMI's NT Forth (Beta, May 1994), two systems
   written in assembly, and with two systems written in C: PFE-0.9.11
   (compiled with @code{gcc-2.6.3} with the default configuration for
   Linux: @code{-O2 -fomit-frame-pointer -DUSE_REGS}) and ThisForth Beta
   (compiled with gcc-2.6.3 -O3 -fomit-frame-pointer). We benchmarked
   Gforth, PFE and ThisForth on a 486DX2/66 under Linux. Kenneth O'Heskin
   kindly provided the results for Win32Forth and NT Forth on a 486DX2/66
   with similar memory performance under Windows NT.
    
   We used four small benchmarks: the ubiquitous Sieve; bubble-sorting and
   matrix multiplication come from the Stanford integer benchmarks and have
   been translated into Forth by Martin Fraeman; we used the versions
   included in the TILE Forth package; and a recursive Fibonacci number
   computation for benchmark calling performance. The following table shows
   the time taken for the benchmarks scaled by the time taken by Gforth (in
   other words, it shows the speedup factor that Gforth achieved over the
   other systems).
   
   @example
   relative             Win32-        NT               This-
     time     Gforth     Forth     Forth       PFE     Forth
   sieve        1.00      1.30      1.07      1.67      2.98
   bubble       1.00      1.30      1.40      1.66
   matmul       1.00      1.40      1.29      2.24
   fib          1.00      1.44      1.26      1.82      2.82
   @end example
   
   You may find the good performance of Gforth compared with the systems
   written in assembly language quite surprising. One important reason for
   the disappointing performance of these systems is probably that they are
   not written optimally for the 486 (e.g., they use the @code{lods}
   instruction). In addition, Win32Forth uses a comfortable, but costly
   method for relocating the Forth image: like @code{cforth}, it computes
   the actual addresses at run time, resulting in two address computations
   per NEXT (@pxref{System Architecture}).
   
   The speedup of Gforth over PFE and ThisForth can be easily explained
   with the self-imposed restriction to standard C (although the measured
   implementation of PFE uses a GNU C extension: global register
   variables), which makes efficient threading impossible.  Moreover,
   current C compilers have a hard time optimizing other aspects of the
   ThisForth source.
   
   Note that the performance of Gforth on 386 architecture processors
   varies widely with the version of @code{gcc} used. E.g., @code{gcc-2.5.8}
   failed to allocate any of the virtual machine registers into real
   machine registers by itself and would not work correctly with explicit
   register declarations, giving a 1.3 times slower engine (on a 486DX2/66
   running the Sieve) than the one measured above.
   
 @node Bugs, Pedigree, Internals, Top  @node Bugs, Pedigree, Internals, Top
 @chapter Bugs  @chapter Bugs
   
   Known bugs are described in the file BUGS in the Gforth distribution.
   
   If you find a bug, please send a bug report to !!. A bug report should
   describe the Gforth version used (it is announced at the start of an
   interactive Gforth session), the machine and operating system (on Unix
   systems you can use @code{uname -a} to produce this information), the
   installation options (!! a way to find them out), and a complete list of
   changes you (or your installer) have made to the Gforth sources (if
   any); it should contain a program (or a sequence of keyboard commands)
   that reproduces the bug and a description of what you think constitutes
   the buggy behaviour.
   
   For a thorough guide on reporting bugs read @ref{Bug Reporting, , How
   to Report Bugs, gcc.info, GNU C Manual}.
   
   
 @node Pedigree, Word Index, Bugs, Top  @node Pedigree, Word Index, Bugs, Top
 @chapter Pedigree  @chapter Pedigree
   
   Gforth descends from BigForth (1993) and fig-Forth. Gforth and PFE (by
   Dirk Zoller) will cross-fertilize each other. Of course, a significant part of the design of Gforth was prescribed by ANS Forth.
   
   Bernd Paysan wrote BigForth, a child of VolksForth.
   
   VolksForth descends from F83. !! Authors? When?
   
   Laxen and Perry wrote F83 as a model implementation of the
   Forth-83 standard. !! Pedigree? When?
   
   A team led by Bill Ragsdale implemented fig-Forth on many processors in
   1979. Dean Sanderson and Bill Ragsdale developed the original
   implementation of fig-Forth based on microForth.
   
   !! microForth pedigree
   
   A part of the information in this section comes from @cite{The Evolution
   of Forth} by Elizabeth D. Rather, Donald R. Colburn and Charles
   H. Moore, presented at the HOPL-II conference and preprinted in SIGPLAN
   Notices 28(3), 1993.  You can find more historical and genealogical
   information about Forth there.
   
 @node Word Index, Node Index, Pedigree, Top  @node Word Index, Node Index, Pedigree, Top
 @chapter Word Index  @chapter Word Index
   
   This index is as incomplete as the manual. Each word is listed with
   stack effect and wordset.
   
   @printindex fn
   
 @node Node Index,  , Word Index, Top  @node Node Index,  , Word Index, Top
 @chapter Node Index  @chapter Node Index
   
   This index is even less complete than the manual.
   
 @contents  @contents
 @bye  @bye
   

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