fig-forth-glossary.txt

This glossary contains all of the word definitions in Release 1 of
fig-FORTH. The definitions are presented in the order of their ascii sort.
Dated: 1979-MAY.
Copyright: See DISTRIBUTION in figdoc.txt 
OCER-ed by Albert van der Horst DFW The Netherlands 2000-MAR

The first line of each entry shows a symbolic description of the action of
the proceedure on the parameter stack. The symbols indicate the order in
which input parameters have been placed on the stack. Three dashes "---"
indicate the execution point; any parameters left on the stack are listed.
In this notation, the top of the stack is to the right.


The symbols include:

addr   memory address
b      8 bit byte (i.e. hi 8 bits zero)
c      7 bit ascii character (hi 9 bits zero)
d      32 bit signed double integer} most significant portion with sign
        on top of stack.
f      boolean flag. 0=false, non-zero=true
ff     boolean false flag=0
n      16 bit signed integer number
u      16 bit unsigned integer
tf     boolean true flag=non-zero

The capital letters on the right show definition characteristics:

C      May only be used within a colon definition. A digit indicates number
       of memory addresses used, if other than one.
E      Intended for execution only.
L0     Level Zero definition of FORTH-78
L1     Level One definition of FORTH-78
P      Has precedence bit set. Will execute even when compiling.
U      A user variable.


Unless otherwise noted, all references to numbers are for 16 bit signed
integers. On 8 bit data bus computers, the high byte of a number is on top
of the stack, with the sign in the leftmost bit. For 32 bit signed double
numbers, the most significant part (with the sign) is on top.

All arithmetic is implicitly 16 bit signed integer math, with error and
under-flow indication unspecified.

!              n  addr  ---                     L0
        Store 16 bits of n at address. Pronounced "store".


!CSP
        Save the stack position in CSP. Used as part of the compiler
        security.


#              d1  ---  d2                       L0
        Generate from a double number d1, the next ascii character which is
        placed in an output string. Result d2 is the quotient after division
        by BASE, and is maintained for further processing. Used between <#
        and #>.
        See #S.


#>             d  ---  addr  count              L0
        Terminates numeric output conversion by dropping d, leaving the text
        address and character count suitable for TYPE.


#S             d1  ---  d2                       L0
        Generates ascii text in the text output buffer, by the use of #,
        until a zero double number n2 results.
        Used between <# and #>.


'              ---  addr                       P,L0
        Used in the form: .
        ' nnnn
        Leaves the parameter field address of dictionary word nnnn.
        As a compiler directive, executes in a colon-definition to compile
        the address as a literal. If the word is not found after a search of
        CONTEXT and CURRENT, an appropriate error message is given.
        Pronounced "tick".


(                                               P,L0
        Used in the form:
        ( cccc)
        Ignore a comment that will be delimited by a right
        parenthesis on the same line. May occur during execution or in a
        colon-definition. A blank after the leading parenthesis is required.


(.")                                              C+
        The run-time proceedure, compiled by ." which transmits the
        following in-line text to the selected output device. See .'"


(;CODE)                                           C
        The run-time proceedure, compiled by ;CODE, that rewrites the code
        field of the most recently defined word to point to the following
        machine code sequence. See ;CODE.


(+LOOP)      n  ---                             C2
        The run-time proceedure compiled by +LOOP, which increments the loop
        index by n and tests for loop completion. See +LOOP.


(ABORT)
        Executes after an error when WARNING is -1. This word normally
        executes ABORT, but may be altered (with care) to a user's
        alternative proceedure.


(DO)                                             C
        The run-time proceedure compiled by DO which moves the loop control
        parameters to the return stack. See DO.


(FIND)  addr1 addr2 --- pfa b tf (ok)
        addr1 addr2 .--- ff (bad)
        Searches the dictionary starting at the name field address addr2,
        matching to the text at addr1. Returns parameter field address,
        length byte of name field and boolean true for a good match. If no
        match is found, only a boolean false is left.


(LINE) n1 n2 --- addr count
        Convert the line number n1 and the screen n2 to the disc buffer
        address containing the data. A count of 64 indicates the full line
        text length.


(LOOP)                                          C2
        The run-time proceedure compiled by LOOP which increments the loop
        index and tests for loop completion.
        See LOOP.


(NUMBER) d1 addr1 --- d2 addr2
        Convert the ascii text beginning at addr1+l with regard to BASE. The
        new value is accumulated into double number d1, being left as d2.
        Addr2 is the address of the first unconvertable digit. Used by
        NUMBER.


*             n1  n2  ---  prod               L0
        Leave the signed product of two signed numbers.


*/            n1  n2  n3  ---  n4             L0
        Leave the ratio n4 = n1*n2/n3 where all are signed numbers.
        Retention of an intermediate 31 bit product permits greater accuracy
        than would. be available with the sequence:
                n1  n2  *  n3  /



*/MOD n1 n2 n3 --- n4 n5 L0
        Leave the quotient n5 and remainder n4 of the operation n1*n2/n3 A
        31 bit intermediate product is used as for */.


+             n1  n2  ---  sum                L0
        Leave the sum of n1+n2.


+!     n  addr  ---                     L0
        Add n to the value at the address.
        Pronounced "plus-store".


+-            n1  n2  ---  n3
        Apply the sign of n2 to n1, which is left as n3.


+BUF add1 --- addr2 f
        Advance the disc buffer address addr1 to the address of the next
        buffer addr2. Boolean f is false when addr2 is the buffer presently
        pointed to by variable PREV.


+LOOP n1 --- (run)   addr n2 --- (compile) P,C2,L0
        Used in a colon-definition in the form:
        DO ... n1 +LOOP
        At run-time, +LOOP selectively controls branching
        back to the corresponding DO based on n1, the loop index and the
        loop limit. The signed increment n1 is added to the index and the
        total compared to the limit.
        The branch back to DO occurs until the new index is equal to or
        greater than the limit (n1>0), or until the new index is equal to or
        less than the limit (n1<0). Upon exiting the loop, the parameters
        are discarded and execution continues ahead.


        At compile time, +LOOP compiles the run-time word (+LOOP) and the
        branch offset computed from HERE to the address left on the stack by
        DO. n2 is used for compile tine error checking.


+ORIGIN n --- addr
        Leave the memory address relative by n to the origin parameter area.
        n is the minimum address unit, either byte or word. This definition
        is used to access or modify the boot-up parameters at the origin
        area.


,             n  ---           ,                L0
        Store n into the next available dictionary memory cell, advancing
        the dictionary pointer. (comma)


-             n1  n2  ---  diff               L0
        Leave the difference of n1-n2.

        
-->                                         P,L0
        Continue interpretation with the next disc screen. (pronounced
        next-screen).


-DUP n1 -- n1 (if zero) n1 -- n1 n1 (non-zero) L0
        Reproduce n1 only if it is non-zero.
        This is usually used to copy a value just before IF, to eliminate
        the need for an ELSE part to drop it.


-FIND --- pfa b tf (found) --- ff (not found)
        Accepts the next text word (delimited by blanks) in the input stream
        to HERE, and searches the CONTEXT and then CURRENT vocabularies
        for a matching entry. If found, the dictionary entry's parameter
        field address, its length byte, and a boolean true is left.
        Otherwise, only a boolean false is left.


-TRAILING addr n1 --- addr n2
        Adjusts the character count n1 of a text string beginning address to
        suppress the output of trailing blanks. i.e. the characters at
        addr+n1 to addr+n2 are blanks.


.             n  ---                            L0
        Print a number from a signed l6 bit two's complement value,
        converted according to the numeric BASE.
        A trailing blanks follows.
        Pronounced "dot".


."                                            P,L0
        Used in the form:
            .', cccc"
        Compiles an in-line string cccc (delimited by the trailing ") with
        an execution proceedure to transmit the text to the selected output
        device.
        If executed outside a definition, ." will immediately print the text
        until the final ',. The maximum number of characters may be an
        installation dependent value. See (.").


-LINE line scr --
        Print on the terminal device, a line of text from the disc by its
        line and screen number. Trailing blanks are suppressed.


.R            n1  n2  ---
        Print the number n1 right aligned in a field whose width is n2. No
        following blank is printed.


/             n1  n2  ---  quot                L0
        Leave the signed quotient of n1/n2.


/MOD n1 n2 --- rem quot L0
        Leave the remainder and signed quotient of n1/n2. The remainder has
        the sign of the dividend.


0 1 2 3 --- n
        These small numbers are used so often that is is attractive to
        define them by name in the dictionary as constants.


0<            n  ---  f                        L0
        Leave a true flag if the number is less than zero (negative),
        otherwise leave a false flag.


0=            n  ---  f                        L0
        Leave a true flag is the number is equal to zero, otherwise leave a
        false flag.


0BRANCH       f  ---                            C2
        The run-time proceedure to conditionally branch. If f is false
        (zero), the following in-line parameter is added to the interpretive
        pointer to branch ahead or back. Compiled by IF, UNTIL, and WHILE.


1+            n1  ---  n2                      L1
        Increment n1 by l.


2+            n1  ---  n2
        Leave n1 incremented by 2.


:                                           P,E,L0
        Used in the form called a colon-definition:
                   : cccc     ...     ;
        Creates a dictionary entry defining cccc as equivalent to the
        following sequence of Forth word definitions '...' until the next
        ';' or ';CODE'.
        The compiling process is done by the text interpreter as long as
        STATE is non-zero. Other details are that the CONTEXT vocabulary is
        set to the CURRENT vocabulary and that words with the precedence bit
        set (P) are executed rather than being compiled.


;                                           P,C,L0
        Terminate a colon-definition and stop further compilation. Compiles
        the run-time ;S.


;CODE                                       P,C,L0
        Used in the form:
           : cccc .... ;CODE
        assembly mnemonics Stop compilation and terminate a new defining
        word cccc by compiling (;CODE). Set the CONTEXT vocabulary to
        ASSEMBLER, assembling to machine code the following mnemonics.

        When cccc later executes in the form:
                              cccc nnnn
        the word nnnn will be created with its execution proceedure given by
        the machine code following cccc.
        That is, when nnnn is executed, it does so by jumping to the code
        after nnnn. An existing defining word must exist in cc prior to
        ;CODE


;S                                            P,L0
        Stop interpretation of a screen.
        ;S is also the run-time word compiled at the end of a
        colon-definition which returns execution to the calling proceedure.


<             n1  n2  ---  f                   L0
        Leave a true flag if n1 is less than n2; otherwise leave a false
        flag.


<#                                              L0
        Setup for pictured numeric output formatting using the words:
            <# # #S SIGN #>
        The conversion is done on a double number producing
        text at PAD.


<BUILDS                                      C,L0
        Used within a colon-definition:
                        : cccc  <BUILDS  ...
                                 DOES>     ...    ;
        Each time cccc is executed, <BUILDS defines a new word with a
        high-level execution proceedure. Executing cccc in the form:
                     cccc nnnn
        uses <BUILDS to create a dictionary entry for nnnn with a call to
        the DOES> part for nnnn. When nnnn is later executed, it has the
        address of its parameter area on the stack and executes the words
        after DOES> in cccc. <BUILDS and DOES> allow runtime proceedures to
        written in high-level rather than in assembler code (as required by
        ;CODE).


=             n1  n2  ---  f                  L0
        Leave a true flag if n1=n2; otherwise leave a false flag.


>             n1  n2  ---  f                   L0
        Leave a true flag if n1 is greater than n2; otherwise a false flag.


>R            n  ---                         C,L0
        Remove a number from the computation stack and place as the most
        accessable on the return stack. Use should be balanced with R> in
        the same definition.


?             addr  --                         L0
        Print the value contained at the address in free format according to
        the current base.


?COMP
        Issue error message if not compiling.


?CSP
        Issue error message if stack position differs from value saved in
        CSP.


ERROR  f n --
        Issue an error message number n, if the boolean flag is true.


?EXEC
        Issue an error message if not executing.


?LOADING
        Issue an error message if not loading


?PAIRS n1 n2 --
        Issue an error message if n1 does not equal n2. The message
        indicates that compiled conditionals do not match.


?STACK
        Issue an error message is the stack is out of bounds. This
        definition may be installation dependent.


?TERMINAL --- f
        Perform a test of the terminal keyboard for actuation of the break
        key. A true flag indicates actuation.
        This definition is installation dependent.


@           addr  ---  n                       L0
        Leave the 16 bit contents of address.


ABORT                                           L0
        Clear the stacks and enter the execution state. Return control to
        the operators terminal, printing a message appropriate to the
        installation.


ABS           n  ---  u                        L0
        Leave the absolute value of n as u.


AGAIN addr n --- (compiling) P,C2,L0
        Used in a colon-definition in the form:
                         BEGIN ... AGAIN
        At run-time, AGAIN forces execution to return to corresponding
        BEGIN.
        There is no effect on the stack. Execution cannot leave this loop
        (unless R> DROP is executed one level below).

        At compile time, AGAIN compiles BRANCH with an offset from HERE to
        addr. n is used for compile-time error checking.


ALLOT         n  ---                           L0
        Add the signed number to the dictionary pointer DP. May be used to
        reserve dictionary space or re-origin memory. n is with regard to
        computer address type (byte or word).


AND           n1  n2  ---  n2                  L0
        Leave the bitwise logical and of n1 and n2 as n3.


B/BUF --- n
        This constant leaves the number of bytes per disc buffer, the byte
        count read from disc by BLOCK.


B/SCR --- n
        This constant leaves the number of blocks per editing screen. By
        convention, an editing screen is 1O24 bytes organized as 16 lines of
        64 characters each.


BACK addr --
        Calculate the backward branch offset from HERE to addr and compile
        into the next available dictionary memory address.


BASE          ---  addr                      U,L0
        A user variable containing the current number base used for input
        and output conversion.


BEGIN         ---  addr  n  (compiling)     P,L0
        Occurs in a colon-definition in form:
           BEGIN ... UNTIL
           BEGIN ... AGAIN
           BEGIN ... WHILE ... REPEAT
        At run-time, BEGIN marks the start of a sequence that may be
        repetitively executed. It serves as a return point from the
        corresponding UNTIL, AGAIN or REPEAT. When executing UNTIL, a return
        to BEGIN will occur if the top of the stack is false;
        for AGAIN and REPEAT a return to BEGIN always occurs.

        At compile time BEGIN leaves its return address and n for compiler
        error checking.


BL            ---  c
        A constant that leaves the ascii value for "blank".


BLANKS addr count --
        Fill an area of memory beginning at addr with blanks.


BLK           ---  addr                      U,L0
        A user variable containing the block number being interpreted. If
        zero, input is being taken from the terminal input buffer.


BLOCK         n  ---  addr                     L0
        Leave the memory address of the block buffer containing block n. If
        the block is not already in memory, it is transferred from disc to
        which ever buffer Was least recently written. If the block occupying
        that buffer has been marked as updated, it is rewritten to disc
        before block n is read into the buffer. See also BUFFER, R/W UPDATE
        FLUSH


BLOCK-READ
BLOCK-WRITE
        These are the preferred names for the installation dependent code to
        read and write one block to the disc.


BRANCH                                       C2,L0
        The run-time proceedure to unconditionally branch. An in-line offset
        is added to the interpretive pointer IP to branch ahead or back.
        BRANCH is compiled by ELSE, AGAIN, REPEAT.


BUFFER n --- addr
        Obtain the next memory buffer, assigning it to block n. If the
        contents of the buffer is marked as updated, it is written to the
        disc The block is not read from the disc.
        The address left is the first cell within the buffer for data
        storage.


C!            b  addr  ---
        Store 8 bits at address. On word addressing computers, further
        specification is necessary regarding byte addressing.


C,            b  ---
        Store 8 bits of b into the next available dictionary byte, advancing
        the dictionary pointer. This is only available on byte addressing
        computers, and should be used with caution on byte addressing mini-
        computers.


C@            addr  ---  b
        Leave the 8 bit contents of memory address. On word addressing
        computers, further specification is needed regarding byte
        addressing.


CFA    pfa --- cfa
        Convert the parameter field address of a definition to its code
        field address.


CMOVE from to count --
        Move the specified quantity of bytes beginning at address from to
        address to. The contents of address from is moved first proceeding
        toward high memory. Further specification is necessary on word
        addressing computers.


COLD
        The cold start proceedure to adjust the dictionary pointer to
        the minimum standard and restart via ABORT.
        May be called from the terminal to remove application programs and
        restart.


COMPILE                                         C2
        When the word containing COMPILE executes, the execution address of
        the word following COMPILE is copied (compiled) into the dictionary.
        This allows specific compilation situations to be handled in
        addition to simply compiling an execution address (which the
        interpreter already does).


CONSTANT     n  ---                           L0
        A defining word used in the form:
                           n CONSTANT cccc
        to create word cccc, with its parameter field containing n. When
        cccc is later executed, it will push the value of n to the stack.


CONTEXT --- addr U,L0
        A user variable containing a pointer to the vocabulary within which
        dictionary searches will first begin.


COUNT addr1 --- addr2 n L0
        Leave the byte address addr2 and byte count n of a message text
        beginning at address addr1. It is presumed that the first byte at
        addr1 contains the text byte count and the actual text starts with
        the second byte.
        Typically COUNT is followed by TYPE.


CR                                              L0
        Transmit a carriage return and line feed to the selected output
        device.


CREATE
        A defining word used in the form:
                           CREATE cccc
        by such words as CODE and CONSTANT to create a dictionary header for
        a Forth definition. The code field contains the address of the words
        parameter field. The new word is created in the CURRENT vocabulary.


CSP           ----  addr                        U
        A user variable temporarily storing the stack pointer position, for
        compilation error checking.


D+ d1 d2 --- dsum
        Leave the double number sum of two double numbers.


D+-           d1  n  ---  d2
        Apply the sign of n to the double number d1, leaving it as d2.


D.            d  ---                            L1
        Print a signed double number from a 32 bit two's complement value.
        The high-order l6 bits are most accessable on the stack. Conversion
        is performed according to the current BASE. A blank follows.
        Pronounced D-dot.


D.R           d  n  ---
        Print a signed double number d right aligned in a field n characters
        wide.


DABS d --- ud
        Leave the absolute value ud of a double number.


DECIMAL                                         L0
        Set the numeric conversion BASE for decimal input-output.


DEFINITIONS                                    L1
        Used in the form:
                        cccc DEFINITIONS
        Set the CURRENT vocabulary to the CONTEXT vocabulary. In the
        example, executing vocabulary name cccc made it the CONTEXT
        vocabulary and executing DEFINITIONS made both specify vocabulary
        cccc.


DIGIT c n1 --- n2 tf (ok) c n1 --- ff (bad)
        Converts the ascii character c (using base n1) to its binary
        equivalent n2, accompanied by a true flag. If the conversion is
        invalid, leaves only a false flag.


DLIST
        List the names of the dictionary entries in the CONTEXT vocabulary.


DLITERAL d --- d (executing) d --- (compiling) P
        If compiling, compile a stack double number into a literal. Later
        execution of the definition containing the literal will push it to
        the stack. If executing, the number will remain on the stack.


DMINUS d1 --- d2
        Convert d1 to its double number two's complement.


DO n1 n2 --- (execute)
        addr n --- (compile) P,C2,L0
        Occurs in a colon-definition in form:
          DO ... LOOP


DO ... +LOOP
        At run time, DO begins a sequence with repetitive execution
        controlled by a loop limit n1 and an index with initial value n2. DO
        removes these from the stack. Upon reaching LOOP the index is
        incremented by one.
        Until the new index equals or exceeds the limit, execution loops
        back to just after DO; otherwise the loop parameters are discarded
        and execution continues ahead. Both n1 and n2 are determined at
        run-time and may be the result of other operations.
        Within a loop 'I' will copy the current value of the index to the
        stack. See I, LOOP, +LOOP, LEAVE.

        When compiling within the colon definition, DO compiles (DO), leaves
        the following address addr and n for later error checking.


DOES>                                           L0
        A word which defines the run-time action within a high-level
        defining word. DOES> alters the code field and first parameter of
        the new word to execute the sequence of compiled word addresses
        following DOES>. Used in combination with <BUILDS. When the DOES>
        part executes it begins with the address of the first parameter of
        the new word on the stack. This allows interpretation using this
        area or its contents. Typical uses include the Forth assembler,
        multidimensional arrays, and compiler generation.


DP            ----  addr                      U,L
        A user variable, the dictionary pointer, which contains the address
        of the next free memory above the dictionary. The value may be read
        by HERE and altered by ALLOT.


DPL           ----  addr                     U,L0
        A user variable containing the number of digits to the right of the
        decimal on double integer input. It may also be used hold output
        column location of a decimal point, in user generated formating. The
        default value on mingle number input is -1.


DR0
DR1
        Installation dependent commands to select disc drives, by presetting
        OFFSET. The contents of OFFSET is added to the block number in BLOCK
        to allow for this selection. Offset is suppressed for error text so
        that is may always originate from drive 0.


DROP          n  ---                           L0
        Drop the number from the stack.


DUMP          addr  n  ---                     L0
        Print the contents of n memory locations beginning at addr. Both
        addresses and contents are shown in the current numeric base.


DUP           n  ---  n  n                     L0
        Duplicate the value on the stack.

                                            .
ELSE addr1 n1 --- addr2 n2
          (compiling) P,C2,L0
        Occurs within a colon-definition in the form:
                         IF ... ELSE ... ENDIF
        At run-time, ELSE executes after the true part following IF. ELSE
        forces execution to skip over the following false part and resumes
        execution after the ENDIF. It has no stack effect.

        At compile-time ELSE emplaces BRANCH reserving a branch offset,
        leaves the address addr2 and n2 for error testing. ELSE also
        resolves the pending forward branch from IF by calculating the
        offset from addr1 to HERE and storing at addr1.


EMIT          c  ---                            L0
        Transmit ascii character c to the selected output device. OUT is
        incremented for each character output.


EMPTY-BUFFERS L0
        Mark all block-buffers as empty, not necessarily affecting the
        contents.
        Updated blocks are not written to the disc. This is also an
        initialization proceedure before first use of the disc.


ENCLOSE addr1 c -- addr1 n1 n2 n3
        The text scanning primitive used by WORD. From the text address
        addr1 and an ascii delimiting character c, is determined the byte
        offset to the first non-delimiter character n1, the offset to the
        first delimiter after the text n2, and the offset to the first
        character not included.
        This proceedure will not process past an ascii 'null', treating it
        as an unconditional delimiter.


END                                        P,C2,L0
        This is an 'alias' or duplicate definition for UNTIL.


ENDIF         addr  n  ---  (compile)   P,CO,L0
        Occurs in a colon-definition in form:
          IF ... ENDIF
          IF ... ELSE ... ENDIF
        At run-time, ENDIF serves only as the destination of a forward
        branch from IF or ELSE. It marks the conclusion of the conditional
        structure. THEN is another name for ENDIF. Both names are supported
        in fig-FORTH. See also IF and ELSE.

        At compile-time, ENDIF computes the forward branch offset from addr
        to HERE and stores it at addr. n is used for error tests.


ERASE addr n --
        Clear a region of memory to zero from addr over n addresses.


ERROR line --- in blk
        Execute error notification and restart of system. WARNING is first
        examined. If 1, the text of line n, relative to screen 4 of drive O
        is printed. This line number may be positive or negative, and beyond
        just screen 4. If WARNING=O, n is just printed as a message number
        (non disc installation). If WARNING is -l, the definition (ABORT) is
        executed, which executes the system ABORT. The user may cautiously
        modify this execution by altering (ABORT).
        fig-FORTH saves the contents of IN and BLK to assist in determining
        the location of the error. Final action is execution of QUIT.


EXECUTE addr -
        Execute the definition whose code field address is on the stack. The
        code field address is also called the compilation address.


EXPECT addr count --- L0
        Transfer characters from the terminal to address, until a "return"
        or the count of characters have been received. One or more nulls are
        added at the end of the text.


FENCE         ---   addr                        U
        A user variable containing an address below which FORGETting is
        trapped. To forget below this point the user must alter the contents
        of FENCE.


FILL addr quan b --
        Fill memory at the address with the specified quantity of bytes b.


FIRST --- n
        A constant that leaves the address of the first (lowest) block
        buffer.


FLD           ---  addr                         U
        A user variable for control of number output field width. Presently
        unused in fig-FORTH.


FORGET                                      E,L0
        Executed in the form:
                        FORGET cccc
        Deletes definition named cccc from the dictionary with all entries
        physically following it. In fig-FORTH, an error message will occur
        if the CURRENT and CONTEXT vocabularies are not currently the same.


FORTH                                         P,L1
        The name of the primary vocabulary.
        Execution makes FORTH the CONTEXT vocabulary. Until additional user
        vocabularies are defined, new user definitions become a part of
        FORTH. FORTH is immediate, so it will execute during the creation of
        a colon-definition, to select this vocabulary at compile time.


HERE          ---  addr                        L0
        Leave the address of the next available dictionary location.


HEX                                             L0
        Set the numeric conversion base to sixteen (hexadecimal).


HLD           ---  addr                        L0
        A user variable that holds the address of the latest character of
        text during numeric output conversion.


HOLD          c  ---                           L0
        Used between <# and #> to insert an ascii character into a pictured
        numeric output string.
        e.g. 2E HOLD will place a decimal point.


I             ---  n                         C,L0
        Used within a DO-LOOP to copy the loop index to the stack. Other use
        is implementation dependent.
        See R.


ID. addr --
        Print a definition's name from its name field address.


IF f --- (run-time)  -- addr n
          (compile) P,C2,L0
        Occurs is a colon-definition in form:
               IF (tp) ...  ENDIF      .
               IF (tp) ... ELSE (fp) ... ENDIF
        At run-time, IF selects execution based on a boolean flag. If f is
        true (non-zero), execution continues ahead thru the true part. If f
        is false (zero), execution skips till just after ELSE to execute
        the false part. After either part, execution resumes after ENDIF.
        ELSE and its false part are optional.; if missing, false execution
        skips to just after ENDIF..

        At compile-time IF compiles 0BRANCH and reserves space for an offset
        at addr. addr and n are used later for resolution of the offset and
        error testing.


IMMEDIATE
        Mark the most recently made definition so that when encountered at
        compile time, it will be executed rather than being compiled. i.e.
        the precedence bit in its header is set.
        This method allows definitions to handle unusual compiling
        situations, rather. than build them into the fundamental compiler.
        The user may force compilation of an immediate definition by
        preceeding it with [COMPILE],


IN            ---  addr                        L0
        A user variable containing the byte offset within the current input
        text buffer (terminal or disc) from which the next text will be
        accepted. WORD uses and moves the value of IN.


INDEX from to --
        Print the first line of each screen over the range from, to. This is
        used to view the comment lines of an area of text on disc screens.


INTERPRET
        The outer text interpreter which sequentially executes or compiles
        text from the input stream (terminal or disc) depending on STATE. If
        the word name cannot be found after a search of CONTEXT and then
        CURRENT it is converted to a number according to the current base.
        That also failing, an error message echoing the name with a " ?"
        will be given.
        Text input will be taken according to the convention for WORD. If a
        decimal point is found as part of a number, a double number value
        will be left. The decimal point has no other purpose than to force
        this action.
        See NUMBER.


KEY           ---  c                            L0
        Leave the ascii value of the next terminal key struck.


LATEST --- addr
        Leave the name field address of the topmost word in the CURRENT
        vocabulary.


LEAVE                                         C,L0
        Force termination of a DO-LOOP at the next opportunity by setting
        the loop limit equal to the current value of the index. The index
        itself remains unchanged, and execution proceeds normally until LOOP
        or +LOOP is encountered.


LFA pfa --- lfa
        Convert the parameter field address of a dictionary definition to
        its link field address.


LIMIT ---- n
        A constant leaving the address just above the highest memory
        available for a disc buffer. Usually this is the highest system
        memory.


LIST          n  ---                            L0
        Display the ascii text of screen n on the selected output device.
        SCR contains the screen number during and after this process.


LIT           ---  n                        C2,L0
        Within a colon-definition, LIT is automatically compiled before each
        16 bit literal number encountered in input text. Later execution of
        LIT causes the contents of the next dictionary address to be pushed
        to the stack.


LITERAL n --- (compiling) P,C2,L0
        If compiling, then compile the stack value n as a 16 bit literal.
        This definition is immediate so that it will execute during a colon
        definition. The intended use is:
              : xxx    [ calculate ]  LITERAL  ;
        Compilation is suspended for the compile time calculation of m
        value.
        Compilation is resumed and LITERAL compiles this value.


LOAD          n  ---                            L0
        Begin interpretation of screen n.
        Loading will terminate at the end of the screen or at ;S. See ;S and
        -->.


LOOP          addr  n  ---  (compiling) P,C2,L0
        Occurs in a colon-definition in form:
                        DO ... LOOP
        At run-time, LOOP selectively controls branching back to the
        corresponding DO based on the loop index and limit. The loop index
        is incremented by one and compared to the limit. The branch back to
        DO occurs until the index equals or exceeds the limit;
        at that time, the parameters are discarded and execution continues
        ahead.

        At compile-time. LOOP compiles (LOOP) and uses addr to calculate an
        offset to DO. n is used for error testing.


M*            n1  n2  ---  d
        A mixed magnitude math operation which leaves the double number
        signed product of two signed number.


M/              d  n1  ---  n2  n3
        A mixed magnitude math operator which leaves the signed remainder n2
        and signed quotient n3 from a double number dividend and divisor n1.
        The  remainder takes its sign from the dividend.


M/MOD ud1 u2 --- u3 ud4
        An unsigned mixed magnitude math operation which leaves a double
        quotient ud4 and remainder u3, from a double dividend ud1 and single
        divisor u2.


MAX           n1  n2  ---  max                L0
        Leave the greater of two numbers.


MESSAGE n --
        Print on the selected output device the text of line n relative to
        screen 4 of drive O. n may be positive or negative. MESSAGE may be
        used to print incidental text such as report headers. If WARNING is
        zero, the message will simply be printed as a number (disc
        unavailable).


MIN           n1  n2  ---  min                 L0
        Leave the smaller of two numbers.


MINUS         n1  ---  n2                      L0
        Leave the two's complement of a number.


MOD           n1  n2  ---  mod                 L0
        Leave the remainder of n1/n2, with the same sign as n1.


MON
        Exit to the system monitor, leaving a re-entry to Forth, if
        possible.


MOVE addr1 addr2 n --
        Move the contents of n memory cells (l6 bit contents) beginning at
        addr1 into n ills beginning at addr2.
        The contents of addr1 is moved first.
        This definition is appropriate on on word addressing computers.


NEXT
        This is the inner interpreter that uses the interpretive pointer IP
        to execute compiled Forth definitions. It is not directly executed
        but is ff the return point for all code proceedures. It acts by
        fetching the address pointed by IP, storing this value in register
        W. It then jumps to the address pointed to by the address pointed to
        by W. W points to the code field of a definition which contains
        the address of the code which executes for that definition.
        This usage of indirect threaded code is a major contributor to the
        power, portability, and extensibility of Forth. Locations of IP and
        W are computer specific.


NFA pfa --- nfa
        Convert the parameter. field address of a definition to its name
        field.


NUMBER        addr   ---   d
        Convert a character string left at addr with a preceeding count, to
        a signed .double number, using the current numeric base. If a
        decimal point is encountered in the text, its position will be
        given in DPL, but no other effect occurs. If numeric conversion is
        not possible, an error message will be given.


OFFSET         ---   addr                            U
        A user variable which may contain a block offset to disc drives. The
        contents of OFFSET is added to the stack number by BLOCK. Messages
        by MESSAGE are independent of OFFSET.
        See BLOCK, DR0, DR1, MESSAGE.


OR             n1   n2  --   or                    L0
        Leave the bit-wise logical or of two l6 bit values.


OUT            ---  addr                            U
        A user variable that contains a value incremented by EMIT. The user
        may alter and examine OUT to control display formating.


OVER nl n2 --- nl n2 n1 L0
        Copy the second stack value, placing it as the new top.


PAD            ---   addr                           L0
        Leave the address of the text output buffer, which is a fixed offset
        above v HERE.


PFA nfa --- pfa
        Convert the name field address of a compiled definition to its
        parameter field address.


POP
        The code sequence to remove a stack value and return to NEXT. POP is
        not directly executable, but is s Forth re-entry point after machine
        code.


PREV ---- addr
        A variable containing the address of the disc buffer most recently
        referenced. The UPDATE command marks this buffer to be later written
        to disc.


PUSH
        This code sequence pushes m3chine registers to the computation stack
        and returns to NEXT. It is not directly executable, but is a Forth
        re-entry point after machine code.


PUT
        This code sequence stores machine register contents over the topmost
        computation stack value and returns to NEXT. It is not directly
        executable, but is a Forth re-entry point after machine code.


QUERY
        Input 80 characters of text (or until a "return") from the operators
        terminal. Text is positioned at the address contained in TIB with IN
        set to zero.


QUIT
        Clear the return stack, stop compilation, and return control to the
        operators terminal. No message is given.


R               ---  n
        Copy the top of the return stack to the computation stack.


R#              ---  addr                            U
        A user variable which may contain the location of an editing cursor,
        or other file related function.


R/W addr blk f --
        The fig-FORTH standard disc read-write linkage. addr specifies the
        source or destination block buffer, blk is the sequential number of
        the referenced block; and f is a flag for f=O write and f=l read.
        R/W determines the location on mass storage, performs the read-write
        and performs any error checking.


R>             ---  n                            L0
        Remove the top value from the return stack and leave it on the
        computation stack. See >R and R.


R0             ---  addr                          U
        A user variable containing the initial location of the return stack.
        Pronounced R-zero. See RP!


REPEAT addr n --- (compiling) P,C2
        Used within a colon-definition in the form:
                          BEGIN ... WHILE ... REPEAT
        At run-time, REPEAT forces an unconditional branch back to just
        after the corresponding BEGIN.

        At compile-time, REPEAT compiles BRANCH and the offset from HERE to
        addr. n is used for error testing.


ROT nl n2 n3 --- n2 n3 nl L0
        Rotate the top three values on the stack, bringing the third to the
        top.


RP!
        A computer dependent proceedure to initialize the return stack
        pointer from user variable R0.


S->D          n  ---  d
        Sign extend a single number to form a double number.


SO             ---  addr                          U
        A user variable that contains the initial value for the stack
        pointer.
        Pronounced S-zero. See SP!


SCR           ---   addr                         U
        A user variable containing the screen number most recently reference
        by LIST.


SIGN          n  d  ---  d                      L0
        Stores an ascii "-" sign just before a converted numeric output
        string in the text output buffer when n is negative. n is discarded
        but double number d is maintained. Must be used between <# and #>.


SMUDGE
        Used during word definition to toggle the "smudge bit" in a
        definitions' name field. This prevents an uncompleted definition
        from being found during dictionary searches, until compiling. is
        completed without error.


SP!
        A computer dependent proceedure to initialize the stack pointer from
        SO.


SP@ --- addr
        A computer dependent proceedure to return the address of the stack
        position to the top of the stack, as it was before SP@ was executed.
            (e.g.  1  2  SP@  @  .   .   .     would
            type 2  2   1)


SPACE                                            L0
        Transmit an ascii blank to the output device.


SPACES        n  ---                            L0
        Transmit n ascii blanks to the output device.


STATE         ---  addr                       L0,U
        A user variable containing the compilation state. A non-zero value
        indicates compilation. The value itself may be implementation
        dependent.


SWAP nl n2 --- n2 n1 L0
        Exchange the top two values On the stack.


TASK
        A no-operation word which can mark the boundary between
        applications.
        By forgetting TASK and re-compiling, an application can be discarded
        in its entirety.


THEN                                        P,CO,L O
        An alias for ENDIF.


TIB           ---  addr                          U
        A user variable containing the address of the terminal input buffer.


TOGGLE  addr b --
        Complement the contents of addr by the bit pattern b.


TRAVERSE addr1 n --- addr2
        Move across the name field of a fig-FORTH variable length name
        field.
        addr1 is the address of either the length byte or the last letter.
        If n=1, the motion is toward hi memory; if n=-l, the motion is
        toward low memory. The addr2 resulting is address of the other end
        of the name.


TRIAD scr --
        Display on the selected output device the three screens which
        include that numbered scr, beginning with a screen evenly divisible
        by three. Output is suitable for source text records, and includes a
        reference line at the bottom taken from line 15 of screen4.


TYPE addr count --- L0
        Transmit count characters from addr to the selected output device.


U*            u1  u2  ---  ud
        Leave the unsigned double number product of two unsigned numbers.


U/  ud u1 --- u2 u3
        Leave the unsigned remainder u2 and unsigned quotient u3 from the
        unsigned double dividend ud and unsigned divisor u1.


UNTIL f --- (run-time)
          addr n --- (compile) P,C2,L0
        Occurs within a colon-definition in the form:
                        BEGIN ... UNTIL
        At run-time, UNTIL controls the conditional branch back to the
        corresponding BEGIN. If f is false, execution returns to just after.
        BEGIN;
        if true, execution continues ahead.

        At compile-time, UNTIL compiles (0BRANCH) and an offset from HERE to
        addr. n is used for error tests.


UPDATE                                          L0
        Marks the most recently referenced block (pointed to by PREV) as
        altered. The block will subsequently be transferred automatically to
        disc should its buffer be required for storage of a different block.


USE --- addr
        A variable containing the address of the block buffer to use next,
        as the least recently written.


USER          n  ---                            L0
        A defining word used in the form:
                        n USER cccc
        which creates a user variable cccc.
        The parameter field of cccc contains n as a fixed offset relative to
        the user pointer register UP for this user variable. When cccc is
        later executed, it places the sum of its offset and the user area
        base address on the stack as the storage address of that
        particular variable.


VARIABLE                                     E,LU
        A defining word used in the form:
                          n VARIABLE cccc
        When VARIABLE is executed, it creates the definition cccc with its
        parameter field initialized to n. When cccc is later executed, the
        address of its parameter field (containing n) is left on the stack,
        so that a fetch or store may access this location.


VOC-LINK --- addr U
        A user variable containing the address of a field in the definition
        of the most recently created vocabulary. All vocabulary names are
        linked by these fields to allow control for FORGETting thru multiple
        vocabularies.


VOCABULARY                                    E,L
        A defining word used in the form:
                     VOCABULARY cccc
        to create a vocabulary definition cccc. Subsequent use of cccc will
        make it the CONTEXT vocabulary which is searched first by INTERPRET.
        The sequence "cccc DEFINITIONS" will also make cccc the CURRENT
        vocabulary into which new definitions are placed.

        In fig-FORTH, cccc will be so chained as to include all definitions
        of the vocabulary in which cccc is itself defined. All vocabularys
        ultimately chain to Forth. By convention, vocabulary names are to be
        declared IMMEDIATE. See VOC-LINK.


VLIST
        List the names of the definitions in the context vocabulary. "Break"
        will terminate the listing.


WARNING       ---  addr                         U
        A user variable containing a value controlling messages. If = 1 disc
        is present, and screen 4 of drive 0 is the base location for
        messages. If = 0, no disc is present and messages will be presented
        by number. If = -1, execute (ABORT) for a user specified proceedure.
        See MESSAGE, ERROR.


WHILE   f --- (run-time)
            ad1 nl --- ad1 n1 ad2 n2 p,C2
        Occurs in a colon-definition in the form:
                  BEGIN ... WHILE (tp) ... REPEAT
        At run-time, WHILE selects conditional execution based on boolean
        flag f. If f is true (non-zero), WHILE continues execution of the
        true part thru to REPEAT, which then branches back to BEGIN. If f is
        false (zero), execution skips to just after REPEAT, exiting the
        structure.

        At compile time, WHILE emplaces (0BRANCH) and leaves ad2 of the
        reserved offset. The stack values will be resolved by REPEAT.


WIDTH         ---  addr                          U
        In fig-FORTH, a user variable containing the maximum number of
        letters saved in the compilation of a definitions' name. It must be
        1 thru 31, with a default value of 31. The name character count and
        its natural characters are saved, up to the value in WIDTH. The
        value may be changed at any time within the above limits.


WORD          c  ---                            L0
        Read the next text characters from the input stream being
        interpreted, until a delimiter c is found, storing the packed
        character string beginning at the dictionary buffer HERE. WORD
        leaves the character count in the first byte, the characters, and
        ends with two or more blanks. Leading occurrences of c are ignored.
        If BLK is zero text is taken from the terminal input buffer,
        otherwise from the disc block stored in BLK.
        See BLK, IN.


X
        This is pseudonym for the "null" or dictionary entry for a name of
        one character of ascii null. It is the execution proceedure to
        terminate interpretation of a line of text from the terminal or
        within a disc buffer, as both buffers always have a null at the
        end.


XOR           nl  n2  ---  xor                 L1
        Leave the bitwise logical exclusive or of two values.


[                                               P,L1
        Used in a colon-definition in form:
                           :  xxx    [  words   ]    more   ;
        Suspend compilation. The words after [ are executed, not compiled.
        This allows calculation or compilation exceptions before resuming
        compilation with ] .  See LITERAL, ].


[COMPILE]                                       p,C
        Used in a colon-definition in form:
                         :  xxx    [COMPILE]   FORTH   ;
        [COMPILE] will force the compilation of an immediate definitions,
        that would otherwise execute during compilation. The above example
        will select the FORTH vocabulary then xxx executes, rather than at
        compile time.


]                                                 L1
        Resume compilation, to the completion of a colon-definition.
        See [.