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Getting Started For beginners 1 Disassembler 2 Entering Numeric values 2 Printing strings 3 Numerics in strings 3 Printing Numeric values 3 Defining new words 5 LINK 5 Using the editor 6 Comments in Code 18 Debug utilities Dumping memory and stack 8 Dump Dictionary 8 DEBUG; TRACEON; TAG 8 TRACEL 9 TM, TD, and SYNONYM 9 differences from normal 10 Variables and Constants 12 BLOCK 12 CONST 12 ,CONST ( comma const) 13 Other Words FLOAD 15 ON REDEFINE 15 OFF PRINTLOAD 15 OMIT 16 Writing Assembly code BLOAD 15 :EXIT and :ENTER 16 Inline Assembler 16 Cross Compile Mode CROSS-COMPILE & UNCROSS 17 LOAD & ISAVE 17 STATUS 19 MAP 19 4TH_86 ( based upon United Controls Corporation CP/M80 Forth.) Translated for IBM PC with EGA graphics. ( Demo ) Version 4.01 December 1993 by M.F.Buchan Kinnell House 1 Argyle Place, Rothesay, Isle of Bute, PA20 0AZ, Scotland, U.K. Voice: 44-700-505185 Fax: 44-700-504051 Compuserve 100012,651 Internet: larryb@rothesay.demon.co.uk Translation Copyright (c) 1988, 1989, 1993, M.F.Buchan Original Copyright (c) 1982 United Controls Corporation, Huntsville, Alabama. 4th_86 GETTING STARTED page 1 The manual provided with this demo version is limited in content. The full manual is being updated at the moment and will be available with registered versions. =============== Getting Started =============== The registered package provides three versions of the system. 4TH_86.COM, 4TH_86DD.COM, and 4TH_86FP.COM. The first is a very minimal system with no disassembler; DOS shell; etc. 4TH86DD has everything except floating point; double precision; and transcendental functions. These are added to create 4TH_86FP.COM. The downloadable demonstration version 4TH86DEM.COM is essentially the same as 4TH_86FP.COM -- but starts in tutorial mode -- uses only page0 video as default -- has additional promotional text added -- a 10 second delay on exit -- and has certain other limitations as a consequence. From the DOS prompt, type 4TH86DEM <return> and you will be in 4th_86. If you want to get back to DOS, type BYE. (QUIT has been re- named to Q-U-IT as it is no longer a preferred exit word] If you are using the DEMO version you will be automatically placed in the split-screen tutorial mode. To exit this type UNSPLIT. The tutorial can always be re-entered at any time by typing HELP. The system words DIR and TYPE can be used from within 4th_86 and paths are now implemented. Drive letters from A: through D: are implemented and can be used alone to change default drive, or as prefix with DIR and TYPE. CD can be used to change directory, but facilities like MD, RD, and REName and COPY are done by shelling to DOS first, using the word SYS The screen contents can be dumped to printer using the normal IBM-PC keyboard keys SHIFT PRTSC. Also CTRL-P will toggle on and off duplication of screen output to printer. ============= For beginners ============= If you are not familiar at all with FORTH as a language, then a good book to read is FORTH: A text and Reference by Mahlon G. Kelly and Nicholas Spies -- Prentice Hall -- 1986. The following tutorial is not dificult to follow however, and you should work through it as the specific features which make this implementation unique will not be covered in any general text book. You also have the built in help facility. 4th_86 GETTING STARTED page 2 The screen display will be easier to follow if you exit from the default tutorial mode -- by typing FULLSCREEN -- before you try any of the following. Before we get into the basics of FORTH -- let's just have a quick look at the disassembler in order to become familiar with its use. This disassembler will be of enormous help when you come to write your first FORTH definitions of - as they are called - "words". ============ Disassembler ============ "DD" is the 4th_86 word which calls up the diassembler. It must be followed by the word you want to disassemble. To show the use of the disassembler, let us see how the word BYE is made up. Type DD BYE and then press <return>. This will show you that BYE makes use of several other Forth words such as PAGE0, BRKON, SECDELAY. Look at each of these words by typing DD PAGE0 etc. Unlike BYE itself - you will see that PAGE0 and BRKON are pure assembly code. SECDELAY is interesting in that most of it is assembly code -- but a part in the middle is Forth code. It is quite simple to mix assembly and Forth source in this manner. The actual source code for SECDELAY is provided on disk. You can also try DD THREAD, DD COLON, and DD SRET if you wish. In fact you can type DD followed by any 4th_86 word and it will be disassembled. Perhaps a better word to demonstrate how Forth and Assembly can be mixed is the word GC. Type DD GC and then use ctrl-S to pause and start the display. You may get OOPS displayed in the disassembly -- and this simply means that the word which ** should ** appear there has been removed from the dictionary. There are two reasons for doing this -- to save space -- and because a ** very ** large number of the words needed to build up the system from source are of no use at all in normal use. You can not of course disassemble any word which has been removed from the dictionary. The display can be "aborted" at any time by pressing the space bar. Ctrl-S will start and stop the display. Ctrl-C and Ctrl-Brk are normally disabled, as using them would dump you back into DOS. The word BRKON turns the ctrl-Brk facility on again. 4th_86 GETTING STARTED page 3 ======================= Entering Numeric Values ======================= Here is one place that 4th_86 differs from all other Forths. Numbers can be input in Hex, Binary, Decimal or Octal. In 4th_86 considerable flexibility is introduced by using the same notation as when writing ASM code -- a suffix after the number -- 123H -- 123Q ( or 123O) -- 11011B for Hex, Octal, Binary respectively. Decimal is the default, so for 123 decimal just type in 123. ASCII values can be inserted as "A" rather than 41H -- or "B" "C" "D" etc. ================ Printing Strings ================ Unlike standard Forths, the dot-quote word ( ." ) does not double as part of the initial string quote. It is a separate word. 4th_86 => " this is a test" ." Other Forths => ."this is a test" Note also that in 4th_86 a space is needed between the first quote sign and the start of the string text. This is because the leading " is a Forth word just like any other word. The closing " is not a word -- it is an end of string delimiter. =================== Numerics in Strings =================== String values are entered between quotes " this is a test" If it is required to enter specific numeric bytes as part of the string -- for example 0D Hex and 0A Hex -- this is done by using the up-arrow ^ " ^0dh 0ah^this is a test" or " ^13 10^this is a test" The result of course is the same as crlf " this is a test" There is a file on disk called FRENCH.4TH which can be loaded [ type FLOAD FRENCH.4th ] and will demonstrate how special accented characters and ascii graphics can be displayed. 4th_86 GETTING STARTED page 4 ======================= Printing Numeric Values ======================= To print out the value on the TOS (top of stack) the operators .H .L .HB .C and . are provided. .H prints a word in Hex with a leading space. .HB prints a byte in Hex with leading space. A single period . prints the TOS in decimal with a leading space. .C prints the ASCII character if one exists -- but with no leading space. .L is the same as . but without a leading space. It's main purpose is for sending ANSI control codes requiring numeric parameters. A leading space would invalidate the ANSI sequence. Try the following at the 4th86 prompt 20H 16 "C" + + dup .H crlf dup . crlf 30H - .C Try also the following 20H 16 "C" + + dup .h 3 spcs dup . 3 spcs 30h - .c In normal Forths different number bases can not be mixed. It is necessary to define a variable BASE as either HEX DECIMAL etc. 4th_86 does not have this clumsy restriction. Whilst there used to be a variable called BASE in 4th_86 it had nothing to do with number bases, and was never used in normal events. It was the relocation offset used when meta-compiling stand-alone COM programs. It is no longer used in version 4.01. You may have noticed that to the left of the 4th_86 ■ prompt there is a highlighted number, which is usually _0_ This number represents the total number of two byte values pushed on the data stack. ( It can become negative if stack underflow takes place ) Try typing in numbers 2 <return> 3 <return> 4567 <return> A" <return> and watching the depth indication increase. Now print out the stack values one at a time with . . . (or if you prefer it .H .H .H ) and note the depth indication decrease. If you print out a value when the stack is empty you will get a negative value of depth display. 4th_86 GETTING STARTED page 5 One feature of all FORTHs is that an unrecognised entry clears the stack and most other transient variables. Type in 2 3 4 5 <return> to get some values on the stack, then type sgkdfshk <return> [ or some other garbage entry ] and the depth display will become zero. In addition to the auto-depth display, the word DEPTH is available to use within definitions. ================== Defining new words ================== Type : Fred 3 . ; This defines a word Fred -- which simply prints the value 3 Type FRED (or fred FrEd fREd) and you will see 3 printed (out of curiosity, disassemble with DD FRED ) Type : Fred 4 . ; You will be asked if you want to redefine Fred -- answer Y Type FRED and and you will see that 4 is now printed instead of 3 Now type : Larry 4 ; : Tom Larry 2 * . ; and then type TOM You should get an 8 printed -- Larry -- which is 4 -- has been multiplied by 2 Let's redefine LARRY : Larry 6 ; ( and of course answer Y ) Now type TOM --- and you will find that you do not get 12 printed - you still get 8. The redefinition of LARRY from 4 to 6 has not affected the prior definition of TOM. This is the normal way with Forth. When TOM was defined -- it used the IMMEDIATELY PRIOR defined value of LARRY. The redefinition of LARRY ** after ** the definition of TOM does not affect TOM's use of the original LARRY definition. A clearer picture of all the words you have entered can be seen if you type DDICT. Now let's see how we can actually replace the old definition with a new one. 4th_86 GETTING STARTED page 6 ==== LINK ==== Type DD LARRY and you will see the constant 6 type FORGET LARRY and then DD LARRY and you will see that we are now back to our original definition of LARRY as the value 4 type : KEN 6 ; LINK LARRY KEN ( ignore the warning message ) TOM you should get the value 12 printed. All calls to the last LARRY are now diverted to KEN instead. Try DD LARRY and DD KEN. The last word linked can be restored with UNLINK Type UNLINK which unlinks LARRY from KEN type TOM and you should get 8 type DD TOM DD KEN and DD LARRY to confirm ================ Using the editor ================ Make sure you have read and implemented the instructions in INTRO.4TH for configuriing EDITR.BAT and ASMBL.BAT. You must first tell 4th_86 the name of the file you want to edit. The default name built into 4th_86 is EDHELP.TXT -- so if you type EDIT you should get this help message displayed by your editor. The word USING allows you to change the default file name to another one. To edit a different file -- say SQ.4TH -- first type USING SQ.4TH -- then all future uses of the word EDIT (and the words REDIT and RELOAD) will call up the file SQ.4TH. The editor is designed to be much more flexible than this however. After editing a Forth source file, the normal procedure would be to re-load it for testing and debugging. For this purpose, the words RELOAD and REDIT exist. RELOAD behaves the same as FLOAD except that it uses the name already specified by USING. Therefore 4th_86 GETTING STARTED page 7 FLOAD SQ.4TH is the same as having executed USING SQ.4TH and then executing RELOAD REDIT also uses the name specified by the previous USING and is equivalent to EDIT followed by RELOAD. The normal edit => fload => test => re-edit cycle is simplified Try USING SQ.4th FLOAD SQ.4th DD OSQUARE REDIT <==> DD OSQUARE REDIT <==> DD OSQUARE where <==> are the steps to exit from the editor you are using. You will see by the addresses attached to the DD disassembly that each REDIT redefines a new OSQUARE, getting higher and higher in memory. To confirm this -- type DDICT and examine how many copies of the word OSQUARE you have loaded. This multiple redefinition can be avoided by defining a dummy word -- say STRT -- and starting your source file with FORGET STRT Try USING SQ.4TH : STRT ; FLOAD SQ.4TH DD OSQUARE REDIT <==> DD OSQUARE now the re-load of the newly edited file SQ.4TH causes deletion of the previously loaded file. Following this tutorial should now be much easier as a hands-on process. Instead of trying to key into 4th_86 lengthy definitions directly from the keyboard, they can be edited into a test file, and the file loaded. Lower and upper case are equivalent, whether entered from the keyboard or floaded from a file. Of course, case in quoted strings is preserved " Hey There" ." will be printed Hey There - not capitalized nor all lower case. 4th_86 GETTING STARTED page 8 ======================== Dumping memory and stack ======================== DM 8DM and 16DM are memory dumps -- try 2000H 8DM etc. NOTE that there is a number left on the stack after the dump is completed. Use .H to display this value and you will see that it is 2080H. The purpose of this is so that the dump can be continued simply by typing 8DM again [ or 16DM or whatever ]. DS and DDS are stack dumps try 2 3 4 5 DS <return> DS <return> DS <return> DDS <return> DS <return> DS prints out the stack values, and leaves them unchanged DDS (destructive dump stack) prints the values and removes them try 2 3 4 5 <return> DS <return> abcd <return> DS <return> this is a convenient way to clear and reset the stack -- type in any meaningless phrase (i.e. - abcd), press return, and the error message clears the stack. =============== Dump Dictionary =============== Type DDICT and you will be presented with a display of the words in the dictionary, together with the address of the dictionary entry and flag byte (high segment ) and the start offset of the code area ( low segment ). The display has now been arranged to pause every 15 items. RETURN produces the next 15 entries. Any other keypress aborts. Type PDICT DUP and instead of returning all the words in the dictionary, you will just get the addresses for the word DUP. =================== DEBUG; TRACEON; TAG =================== We already have TOM defined Type TRACEON TOM and then TOM the word is traced, and stack values are displayed 4th_86 GETTING STARTED page 9 TRACEOFF removes the trace, and TAG (trace-again) restores it applying TRACEON to another word automatically removes it from the old one any errors -- as well as clearing the stack -- also remove TRACEON DEBUG is an on/off toggle. type TRACEOFF to be sure -- and then type DEBUG ( to toggle debug on) now type 3 4 5 6 <return> . . <return> DDS (return> DEBUG ( to toggle it off) this display of stack contents is useful. ====== TRACEL ====== This is Trace-level and is used for tracing DO...LOOP structures Type : SLOOPY 5 0 do I . loop ; then run it by typing SLOOPY you should get 0 1 2 3 4 5 displayed on the screen now TRACEON SLOOPY SLOOPY -------- not very impressive 3 TRACEL SLOOPY ---- somewhat better ??? =============== TM; TD; SYNONYM =============== Type TM and the time will be shown Type TD <return> and then TD <return> again. the elapsed time between the two events is shown Try : dly1 1000 0 do loop ; : dly td 10 0 do dly1 loop crlf td crlf ; 4th_86 GETTING STARTED page 10 then run by typing DLY. The SECOND line shows the elapsed time to complete the word DLY -- measured between the first TD and the second TD. No -- indeed this system is not as fast as many others -- but at the moment speed is not the objective. The objective is a user-friendly interface which will allow ease of code writing and learning for beginners. So you think TM is too terse and non-standard? well try SYNONYM TIMEELAPSED TD and type TIMEELAPSED -- purists can build synonyms for any word they think "non-standard" (or modify the source) and create a new system file using SAVESYS. 4th_86 GETTING STARTED page 11 ======================= differences from normal ======================= 4th_86 is different from other implementations of FORTH in several ways. Some of the differences are because of the targeted applications of FORTH such as the fact that the dictionary is stored separately from the code so compact stand-alone code can be generated. Other differences arise because of adding features not commonly found in other FORTHs, different naming conventions, and different philosophies in the implementation. Listed below are some of the minor differences that may "disturb" the user of a more conventional FORTH. SYNONYMS or short words can be used to re-define the more familiar names. For example: SYNONYM EMIT .C or : KEY 0 BEGIN DROP 255 6 MON2 DUP END ; After the table below is a discussion of several more significant differences. Many FORTHs 4th_86 exact Equivalent replacement C@ B@ C! B! EMIT .C KEY 0 BEGIN DROP 255 6 MON2 DUP GETCHR END TYPE 1 DO DUPB@ .C 1+ LOOP DROP ." VARIABLE DATA[ ...] CONSTANT CONST ."string" " string" ." ABORT" string" " string" 1 ERMSG LEAVE EXIT BEGIN..UNTIL BEGIN...END BEGIN..WHILE..REPEAT REPEAT..WHILE..ENDWHILE D+ D= etc. ,+ ,= etc. 4th_86 GETTING STARTED page 12 In 4th_86, DO..LOOPs terminate when the loop count is exceeded, not equaled. Also in most FORTHs, the loop is always executed at least once, while in 4th_86 the loop index is checked against the limit before the loop is executed (loop skipped if limit exceeds maximum). In 4th_86, loops cannot use negative increments, When the word EXIT (corresponds to LEAVE) is executed, the loop is exited immediately (most FORTHS set the loop limit equal to the current loop index). The file SHARPS.4th contains source for double precision formatted output routines -- it also includes a self loading and executing demonstration of these. CREATE...DOES is not included as such, but the file ARRAY.4th shows how defining words can be created. This file also contains a self exeuting demonstration. ======================= Variables and Constants ======================= BLOCK ===== Purpose: Reserves a block of contiguous memory where the size of the block is on the TOS and the name of the block is the next word. When the name is executed, the address of the block of memory associated with it is placed on the stack. ?? block_size --- ?? ( when BLOCK is executed ) ?? --- ?? address ( when the name of the block is executed ) Example: Reserve 25 bytes of memory and name it BUFFER. 25 BLOCK BUFFER ( A buffer which is 25 bytes long ) Example: Assume that the address of BUFFER is 453EH. Using the word .H print the address of BUFFER. BUFFER .H 453E ( this is printed on the console ) 4th_86 CONSTANTS AND VARIABLES page 13 CONST ===== Purpose: Defines a constant whose value is on TOS and name follows CONST. When the name is executed, the value associated with that name is placed on TOS. Only single precision integers may be used as the value of a constant. ?? value -- ?? ( when CONST is executed ) ?? -- ?? value ( when name of constant is executed ) Example: Define the constant B_SIZE whose value is 1100. Also, using the word . print the value of SIZE. 1100 CONST B_SIZE B_SIZE . 1100 ( this is printed on console ) ,CONST ( comma const) ====== Purpose: ,CONST is similar to CONST except a double precision constant is defined. ?? --- ?? Format: value ,CONST name DATA[ ( data left bracket) ====== Purpose: Defines a block of memory with the values between DATA[ and ] with the name of the block following ]. The values may be: 1. one byte integers 2. two byte integers 3. strings with a length byte 4. strings without a length byte When the name of the block is executed, the address of the block associated with the name is placed on the TOS 4th_86 CONSTANTS AND VARIABLES page 14 There are special words which allow the data type to vary as mentioned above. The words are: BYTE WORD LENGTH NOLENGTH and are respective to the meanings 1 through 4 above. The defaults are WORD and LENGTH. When these words are detected, all remaining values have the same data type until either a new defining data type is encountered or a ] is found, which ever comes first. Note that ' and " can be used in DATA[ ?? --- ?? Example: Define TABLE whose values and format are: 145 ( one byte) 5394 ( one byte) 13 ( two bytes) " HI" ( with length byte) 423EH ( two bytes) " HELLO" ( no length byte) and write a word, TEST which prints each value one per line. DATA[ BYTE 145 5394 WORD 13 LENGTH " HI" WORD 423EH NOLENGTH " HELLO" ] TABLE : TEST TABLE DUPB@ . CRLF 1+ DUPB@ . CRLF 1+ DUP@ . CRLF 2+ DUP 4 + SWAP DO DUPB@ + 1+ DUP@ .H CRLF 2+ DUP 4 + SWAP DO I B@ ." LOOP ; TEST 145 18 13 HI 423E HELLO 4th_86 OTHER WORDS & FEATURES page 15 ===== FLOAD ===== This has already been described. An alternative to FLOAD FILE.ABC would be " FILE.ABC" LOAD. The use of the word FLOAD avoids the need for string quotes. ON REDEFINE ============ REDEFINE is a flag which determines whether the compiler will give a warning or not when a re-definition is encountered. ON REDEFINE allows words to be redefined without warning. OFF REDEFINE causes warning messages. OFF PRINTLOAD ============= PRINTLOAD is a flag which determines whether the file will be listed on the screen as it is loaded. OFF PRINTLOAD allows the file to load without being displayed on the screen. ON and OFF PRINTLOAD can be scattered throughout a file if parts are to be observed during loading -- as indeed can ON and OFF REDEFINE. ===== BLOAD ===== BLOAD is used for COM files created by MASM. It does ** NOT ** check for re-definition so care is needed not to duplicate words. This feature has been briefly described in INTRO.4TH and will not be elaborated in this shortened manual. In-line assembly is available and will normally be the preferred method. There is however a file TEST.ASM provided, which you can use [ issue the command BLOAD TEST --- do **not** use the .ASM suffix ]. The first time you BLOAD this file it will automatically compile into TEST.BIN [ provided you have configured ASMBL.BAT properly ] and then load the TEST.BIN into 4th_86. By examining the source for TEST.ASM you will see that it defines three words FIRST SECOND and THIRD. If you execute these words they each print a message. BLOAD only compiles the target file into BIN if there is no BIN file already existing -- or if its date is earlier than that of the ASM file. If you use BLOAD TEST again it will no longer compile TEST.ASM -- unless you delete TEST.BIN first -- or edit TEST.ASM to give it a later date. 4th_86 OTHER WORDS & FEATURES page 16 ================ :EXIT and :ENTER ================ These allow changes from assembly to colon ( :ENTER) and from colon to assembly ( :EXIT) within the same word definition. See the file SECDELAY.4TH ==== OMIT ==== As the number of words added to the system increases, it soon becomes necessary to "prune out" the garbage entries in the dictionary. All code entered has a dictionary entry, -- and is referenced by other code. A good 50% of the code entered however will never be needed for external applications, and maintaining a dictionary pointer to it is simply a waste of space. ================ Inline Assembler ================ This feature has again been described briefly in INTRO.4TH and will not be elaborated on in this limited manual. There are however two files MASM.TST and MASMTST which were used in developing the assembler. These can both be FLOADed -- or examined to see the format of entering inline assembly instructions. Both files end by calling upon the disassembler to display the code that was just loaded. The object was to check that the assembler and disassembler were consistent. Many of the source files for the system have both inline assembly; BLOADable assembly; and plain FORTH code. Much can be learned by examining these. ============================= How to compile demonstrations ============================= To create SINE.COM simply bring up 4TH_86 and then type FLOAD SINCOM.DEM The process will end by exiting to DOS. Look at the file SINCOM DEM which automates the building process, and the file SIN.4TH which is the source for the demonstration, to see what is happening. 4th_86 ASSEMBLY & CROSS COMPILE page 17 Similarly you can FLOAD SMITH.DEM to produce SMITH.COM -- and of course FLOAD HILCOM.DEM will produce HILBERT.COM. HILSIER2 is used exclusively by HILCOM.DEM to produce HILBERT.COM -- and omits the facility for defining levels and magnification. If you examine the source code however, you will see commented out the relevant code to allow level and magnification to be specified from the 4th_86 command prompt. You can edit HILSIER2.4TH [ or use HILSIER.4TH ] to reinsert the omitted code - and then reload. The easiest way is by using REDIT as already described. ======================= CROSS-COMPILE & UNCROSS ======================= The demonstrations which you created above were created in CROSS-COMPILE mode. The 4th_86 system provides the user with a means of compiling any system provided either image [ xxx.IMG ] or source code files are available for all the words needed. The cross-compiler is not a separate compiler, instead it is a mode in which the compiler executes. The compiler runs in one of two modes: cross-compile or noncross-compile. Until specified, the compiler will operate in noncross-compile mode. Executing the word CROSS-COMPILE switches to the cross-compile mode. Unlike earlier versions of 4th_86, CROSS-COMPILE now needs no parameters. Because all cross compile activity is in its own dedicated segment, it starts at offset 100H and has it's upper limit close to the 64K offset limit. several points need to be noted a) code generated in cross-compile mode can ** NOT ** be run during the process of cross compiling. All offsets are identical to the final code produced -- but the segment is inappropriate. b) all code forming part of the "mother system" can be run in cross-compile just as in noncross mode. Obvously this is essential or the compiler would be "dead". c) cross-compiled definitions can not reference a word which has not already been itself defined in cross-compile. The word may already exist in the mother system -- and be executable -- but attempts to use it in a cross-compie definition will give an error message. d) Cross-compile creates its own dictionary, and FIND will reference this dictionary to determine code addresses ** NOT ** the system dictionary. The system dictionary is only used for words in immediate mode. 4th_86 ASSEMBLY & CROSS COMPILE page 18 ISAVE ===== This is only used during cross-compile. At any stage of partial completion of the cross-compile, the memory image can be saved by using ISAVE FNAME.IMG ILOAD ===== This allows a previously saved xxx.IMG file to be re-loaded in the cross-compile mode. Unlike earlier versions of 4th_86, image files are not system sensitive because cross compile takes place in a dedicated segment - and always at offset 100H. COMMENTS IN CODE ================ Forth or in-line assembly code between brackets is treated as comments and ignored by FLOAD. for example : comment_test 2 ( first variable ) 3 ( second variable ) dup ( stack is 2 3 3 ) * ( 3 * 3 gives 9 ) + 2 + 9 gives 11 ) . ( print answer ) ; ( end word definition ) To assist in following complicated if -- then -- else and mixed conditional statements; the usual practice of indenting has not been used. Instead the ascii-graphic character B3 Hex [ 179 decimal ] is ignored by 4th_86 when encountered in FLOADed code. This character is a vertical line and its use is shown by the following sample. : DS ( DISPLAY STACK ELEMENTS IN HEX) SP@ CLISP @ SWAP - 2 / DUP 0> IF ( SOMETHING ON STACK) │ │ BEGIN │ │ DUP 1+ PICK .H ( PRINT IT) │ │ 1 - DUP 0= │ END DROP crlf │ ELSE │ │ IF ( underflow) │ │ " STACK UNDERFLOW ... RESETTING STACK." 1 ERMSG │ THEN │ " STACK EMPTY." ." CRLF │ THEN ; 4th_86 ASSEMBLY & CROSS COMPILE page 19 ====== STATUS ====== STATUS is a word which prints out the dictionary and code space available at any stage. In cross-compile mode it prints additional information. === MAP === " xxxx.yyy" MAP will create a file xxxx.yyy showing all the words loaded into a system either in cross-compile or noncross mode. It will not list the words already embedded in the "mother" system. ========== CONCLUSION ========== The main features of 4th_86 have been outlined. The Glossary will define individual words -- and the complete manual will give a description of the memory layout and dictionary structure. 4th_86 INDEX page 20 ,+ ,= etc 11 ,CONST 13 ." 3 .C 4 .H 4 .HB 4 .L 4 . 4 16DM 8 8DM 8 :ENTER 16 :EXIT 16 ^ 3 ARRAY.4th 12 AUTO-DEPTH DISPLAY 4 BASE 4 BLOAD 15 BLOCK 12 BRKON 2 brkon 2 BYE 2 C! 11 C@ 11 CD 1 Colon Definitions 5 COLON 2 CONST 12 CONSTANT 11 CREATE .. DOES 12 ctrl-Break 2 ctrl-Brk 2 ctrl-C 2 CTRL-P 1 ctrl-S 2 D+ D= etc. 11 DATA[ 13 DD 2 DDH 2 DDICT 8 DDL 2 DDS 8 DEBUG 9 DEMO version 1 DEPTH 5 4th_86 INDEX page 21 diassembler 2 DIR 1 DM 8 DO..LOOP 9 DO..LOOPs 12 DS 8 EMIT 11 EXIT 12 FLOAD 15 FLOAD 7 FORGET 6 FRENCH.4TH 3 FULLSCREEN 2 HEAD 15 HILSIER2 17 ILOAD 18 Inline Assembler 16 ISAVE 18 KEY 11 LAST 15 LEAVE 12 LINK 6 LOAD 15 MAP 19 OMIT 16 OOPS 2 PAGE0 2 PDICT 8 PRINTER 1 PRINTLOAD 15 REDEFINE 15 REDIT 6 RELOAD 6 RELOAD 7 SECDELAY.4TH 16 SECDELAY 2 SHARPS.4th 12 SHIFT PRTSC 1 SRET 2 STATUS 19 SYNONYM 10 4th_86 INDEX page 22 SYS 1 TAG 8 TD 9 TEST.ASM 15 THREAD 2 TM 9 TRACEL 9 TRACEOFF 8 TRACEON 8 TYPE 11 TYPE 1 UNLINK 6 UNSPLIT. 1 USING 6 VARIABLE 11