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F83 Users Manual, by the Silicon Valley Users FIG Chapter. Originally in several smaller files. Can use some more text. F83 Users Manual ~~~~~~~~~~~~~~~~ F83 Version 2.0 written by Michael Perry and Henry Laxen This manual was compiled by J. G. Modrow for the SVCS FORTH SIG June 1984 Edited by John A. Peters July 85 Rev. 2.1.x INDEX ~~~~~ 1.0 Introduction 1.1 About F83 2.0 Using F83 2.1 Distribution Disks 2.2 Starting F83 2.3 Standard System Documentation Requirements 2.4 Version 2.0 General Information 2.5 Creating Custom Applications 2.6 Metacompiling F83 2.7 Quick Reference 3.0 Glossary 4.0 MSDOS services 5.0 MSDOS Disk File Interface 6.0 Assembler 7.0 Source Listings 8.0 Forth Books 1.0 Introduction WELCOME TO FORTH ******************************************************************** * * * This is a public domain system, and may be freely distributed * * and copied, as long as the authors are given credit and no * * copyright notice is placed upon it. If we catch someone selling * * this system as their own proprietary product, with their * * copyright notice , we will do our best to make them regret it * * for the rest of their lives. You have been warned!! * * * ******************************************************************** Forth is about ten years old now (1983) but some of the features of F83 are relatively new to the Public Domain Forth Model. If you are new to Forth your best bet is to purchase the book STARTING FORTH by LEO BRODIE. It costs about seventeen dollars and is available at most large book stores. On page 84 you will find the commands for the line editor. The F83 model follows both the book and the Forth 83 standard. See Section 8.0 for addresses of places where you can purchase STARTING FORTH and the FORTH 83 Standard. The Forth Interest Group ( FIG ) has meetings on the 4th Saturday of each month, currently at the Chabot College in Hayward, CA and the DYSAN Auditorium, 5201 Patrick Henry Drive, Santa Clara, CA at 1:00 pm. Call the FIG hot line if you wish to double check the location phone 415- 962-8653 or the FIG Tree BBS (300 baud) at 415-538-3580. Henry Laxen Mike Perry 1259 Cornell Avenue 1125 Bancroft Way Berkeley, CA 94706 Berkeley, CA 94702 1.1 About F83 F83 is an 83 standard Forth with several features not found in other FORTH's. F83 was written and donated to the public domain by Henry Laxen and Mike Perry. There are versions for MSDOS, CP/M-86, CP/M operating systems and other microprocessors. The distribution disk is normally a double sided disk with all the source files compressed except the file expansion utility. File expansion takes a long time because the expansion utility is all in high level code so F83 is being distributed by SVCS on two double sided disks in the expanded form. A Metacompiler and the F83 kernel source code is on one disk and the rest of the files on the other disk. There is only one short text file on one disk that explains the differences between versions 1.0 and 2.0. The source code contains the rest of the system documentation, but more about that later. F83 uses standard operating system files and has the facilities to open, create and close standard files through DOS. No special format FORTH disks are needed. The limit on the number of files that can be open at once is the amount of memory you have for file buffers. Separate input and output file control blocks allow different input and output screen files to be open at the same time. The word BDOS uses Interrupt 33 to provide access to MSDOS functions and make F83 usable on other MSDOS machines. Several words are vectored so that their definitions can be changed to suit your application. The discussion of screen output redirection to the printer later in this article is one illustration of the utility of this technique. The editor is modeled after the one in the book STARTING FORTH by LEO BRODIE. On page 84 you will find the commands for the editor. The F83 model follows both the book and the Forth 83 standard. STARTING FORTH would be a good book for the beginner and the FORTH 83 Standard would be a good reference for any user. Both books are available from many book stores with large computer book sections. If you can not find them try one of the sources listed in Section 8.0. A recursive decompiler is provided. It works fine but lists all the words in line. A super feature that is even more powerful is the ability to display the source code of any F83 word. The command 'VIEW name' will find the source code screen for the word 'name' and list the screen. Another command will list the documentation screen. The implementation of "Shadow Screens" is a very powerful documentation and help feature. F83 source code has a shadow screen containing documentation associated with every screen of source code. The limitation on this technique is that the source files must be in the default disk drive or they will not be found. The words SHADOW SHOW prints a range of source screens and their associated shadow screens side by side on an EPSON or IBM printer. F83 includes all the source code for the system, an Assembler and a Meta Compiler allowing you to customize the system any way you want. These are two very powerful features that are not included with many commercial versions of FORTH. You can delete unneeded words, change functions of words or add functions. You can rewrite the system assembly language level source code in KERNEL86.BLK and CPU8086.BLK and change the assembler in the meta compiler to cross compile a system for a different processor or operating system. The source code for a few words that are different between CP/M-86 and MSDOS is included for both systems so that F83 for either system can be generated. 2.0 Using F83 The following sections attempt to assist you in getting started with F83. With this information you should be able to start-up F83, start poking around and experimenting. Happy computing! 2.1 Distribution Disks The distribution disk for F83 Version 2.0 comes with the files compressed so that everything fits on one disk. You will need to expand the source files so you can list and use them. If you downloaded your system from a BBS you probably received your system in SQueezed format. Additionally it may be a library of files with a .LBR or .LIB extentions. DELBR.COM will extract all the files in a library or you can use NULU.COM to look at the files in a libray without coping them to another disk. However standard forth is 64 columns and the above utilitys usually expect for 80 columns making Forth block files look strangly offset. Hopefully some day Forth will include a variable width editor. A set of files that are SQueezed but not in a library can be most easily UNSQueezed with NSWEEP.COM or S/USQ.COM etc. Some of them have a war to tag a group of files and UNSQueez and copy in mass. If you received your system in the expanded format it will be on two DSDD disks or three SSDD disks. In that case you can skip the huffman unsqueezing instructions and go down to section 2.2 Starting F83. The list of the system and documentation files follows. Compressed: Expanded files: Dsk Description: ----------- --------------- --- ---------------------------------- M86.HUF META86.BLK 2 Metacompiler source code K86.HUF KERNEL86.BLK 2 F83 kernel, code words HF.HUF HUFFMAN.BLK 1 Compression utility source E86.HUF EXTEND86.BLK 1 F83 high level words C86.HUF CPU8086.BLK 1 Utility code words UT.HUF UTILITY.BLK 1 Utility high level words CK.HUF CLOCK.BLK 1 Clock source code FX.HUF F83-FIXS.TXT 1 V2.0 Update documentation F83.COM 1 Executable F83 system, not comprsd KERNEL.COM 2 Compiled F83 kernel The instructions for expanding the compressed files follow. The parts that you type are underlined. The <CR> symbol represents carriage return. The expansion process takes a lot of time because the expansion code is all high level code. So start it and go do something else or relax. Prepare two double sided formatted disks then put your disk with F83.COM and EXPAND86.BLK in disk drive A: and type the following at the DOS prompt. A>F83 EXPAND86.BLK <CR> F83 will load, at the "ok" prompt type "1 LOAD <CR>" and you will create an expansion program named RUNME.COM. To expand the system now type the following at the DOS prompt. A>RUNME <CR> You will get the following instructions to follow. To expand your system, type XYZZY XYZZY <CR> This takes a long long long time, and bells will ring when you are needed, so I suggest you get it started and have a long cool drink. To expand your F83 system, make sure this disk is in drive A: and that an empty, formatted disk is in drive B:. You will need two disks. When ready, press any key to continue. <key stroke> Expanding: M86.HUF into B:META86.BLK Expanding: K86.HUF into B:KERNEL86.BLK [ bells ring ] Your disk is now full, please remove it and insert another empty, formatted disk in drive B: and press any key to continue. <key stroke> Expanding: E86.HUF into B:EXTEND86.BLK Expanding: C86.HUF into B:CPU8086.BLK Expanding: UT.HUF into B:UTILITY.BLK Expanding: HF.HUF into B:HUFFMAN.BLK Expanding: CK.HUF into B:CLOCK.BLK Expanding: FX.HUF into B:F83-FIXS.TXT [ bells ring ] Congratulations, you have a full F83 system. May the Forth be with you. ok 2.2 Starting F83 By now you may have looked at some of the files with the TYPE command. You can have a printout of these instructions by using <Control PrtSc> in MSDOS or Controll P in CP/M and entering TYPE F83.DOC or TYPE F83-FIXS.TXT. In the following text, the <CR> symbol represents the carriage return key. First make a new system disk with COMMAND.COM on it. Copy the files from the disk with F83.COM on it except HUFFMAN.BLK, CLOCK.BLK and EXPAND86.BLK to the new disk. We will call this disk 1. Make a working system disk from the other distribution disk. Copy F83.COM to this disk. We will call this disk 2. F83 does not have or need a default source file name as some commercial versions of FORTH do. No default file extensions are provided either so file names and extensions must be entered. Now to enter Forth from DOS, insert the disk 1 into drive A of your computer, boot it and type at the DOS prompt, A>F83<CR> or A>F83 sourcefile.ext<CR> Forth will reply with: 8086 Forth 83 Model 2.1.0 Modified 01Apr84 Now try out the following words to see how they work and get a feeling for F83. WORDS and A L To see a list of the words that are in the dictionary type WORDS. You will see lots of words. Each word is a command in FORTH. FORTH has different vocabularies so that functions or utilities can be separated without word definitions clashing. Three of these vocabularies are HIDDEN, EDITOR and SHADOW. To list the vocabulary type the vocabulary name then WORDS. To return to the main vocabulary type FORTH <CR>. SEE word There is a decompiler present which reverses the compiling process, producing source code from object code. The user interface to it is the word SEE <name> where <name> is the name of a Forth word you wish to decompile. While the information SEE gives you is not as complete as that given by VIEW, a least it is always available, and not dependent upon whether or not the correct file is present on the currently logged in disk drive. For a real experience try decompiling the words STATUS, which is a DEFERred word, ie. and execution vector. SEE calls itself recursively in this case and tracks down the definition. This can be quite handy. However SEE is not a full decompiler. A definition with a literal number like for example 64 in it, will decompile to LIT 64 and the conditionals like DO, LOOP, IF, ESLE, THEN, BEGIN, WHILE, UNTILL and REPEAT will appear something like (0branch) 4 or (branch) 3. The number is the number of words foreward or back in the definition that the (branch) is spliting to. (or is it the number of words divided by two). Instead of counting, it is usually easier and more acurate to LOCate the word and turn to yur print out or find the disk with the source file and VIEW the word. VIEW word The VIEW command is one of the best features of F83. VIEW <word> <CR> will find the screen that contains the code for the <word>, provided that the file containing <word> is on the currently logged disk drive. If you can fit all of the source code on a single drive, VIEW works great, and takes care of opening the file and displaying the screen for you. If not when View can't find the proper file on line it atleast tells you the name of the files it is looking for along with the screen number. Each word is a command and each can be VIEWed. Let's look at the word SHOW by typing VIEW SHOW. Assuming all is well you will see a Forth screen containing the definition of SHOW along with some other words. Type this: EDITOR VIEW JOIN<CR> A L Type A L <CR> and you will be rewarded with the Shadow screen that goes with the word (command) L. A L <CR> will Alternate List you back to the original screen of code. Look at it and when you see a word that doesn't seem fully self evident, VIEW it and read the shadow screen. You are looking at a screen of editing commands. Lets go to the shadow with the A L command and do some exploring. While we are in the shadows lets look at the next five or six shadow screens that should be editor words. Use N L. N L and B L and N ED Now for some more commands. N is next screen and L is list. N L lists the next screen and B L lists the next screen back. N ED will edit the next screen etc. SHADOW and SHOW word ( COPY, CONVEY ) We have also tried to make extensive use of the shadow screen concept. In this regard, the A word moves you from the current screen to its associated shadow screen. The SHADOW vocabulary contains a bunch of words that are helpful in maintaining shadow screens. COPY allows you to copy not only a screen, but also its associated shadow. SHOW allows you to list each source screen across from its shadow when you want to print them. Finally CONVEY allows you to move groups of screens and their associated shadows. To see what words are in the SHADOW vocabulary simply type SHADOW WORDS <CR>. To view the SHOW word type VIEW SHOW <CR>. The word SHOW and it's source code that we have been viewing, is a command that prints out three source screens along with three shadows for a total of six screens per page. There are two versions of SHOW. The vocabulary you are in determines how SHOW will print out. If you are in the SHADOW vocabulary, three screens of code and three of shadows will print. If you are in FORTH you will get six screens of code with out shadows. This is how yu do it when there are no shadows in the file. If you have a printer you may print the editor screens now as follows. Type VIEW WIPE for example. If wipe is the first of 6 screens of editor words remember the screen number. If for instance it was 80 then type 80 85 SHADOW SHOW <CR> FILE? and DEFAULT FILE? prints the filespec of the current output file and DEFAULT? prints the default disk drive number. FILES? prints the names of both the OPEN and the FROM files. It is defined in TOOLS.BLK FROM filespec FROM d:filename.ext makes "filename" the current input screen file so that you can have different input and output screen files. OPEN filespec OPEN d:filename.ext makes "filename.ext" the current input and output screen file. A: B: and n SELECT You can select the default disk drive from F83 by typing A: for drive A and B: for drive B. 0 SELECT <CR> does the same as A: <CR>. If you want to make drive C the default drive type 2 SELECT. Create the word C: by typing the following definition. : C: 2 SELECT ; <CR> PRINTING ON and PRINTING OFF PRINTING ON turns on the printer enable directing output to the screen and the printer. PRINTING OFF turns printer output off directing all output to the screen. ' (PRINT) IS EMIT and ' (EMIT) IS EMIT and ' (CONSOLE) IS EMIT ' (PRINT) IS EMIT redirects screen output to the printer. Nothing will print on the screen, regardless of the state of PR-IN. ' (CONSOLE) IS EMIT directs output to the screen only, regardless of the state of PRINTING ON or OFF. ' (EMIT) IS EMIT directs output back to the screen. Now PRINTING ON and OFF will function as explained above. Backspace By now you may have noticed that if you make a mistake typing a word the only way to correct it is to type backspace. Backspace backs up the cursor on the screen but does not erase the characters already there. These characters are erased from the input buffer so backspacing and retyping the correct word does work correctly. I find it confusing to have this extra garbage on the screen. The source code to change the backspace to a backspace and delete is in KERNEL86.BLK screens 47 and 48. Type the following to fix F83.COM. HEX 41 112A C! DECIMAL <CR> If you wish to save this change, type SAVE-SYSTEM F83.COM <CR>. The current system image will be saved on the current disk as F83.COM. To fix the source code edit KERNEL86.BLK screen 48 and remetacompile the system. Put disk 2 in drive B: and type B: VIEW CC-FORTH <CR> to view the screen you need to change. You need to change the word BS-IN to (DEL-IN) in the definition of CC-FORTH. You can do this with the editor. Now follow the steps explained in Section 2.6, Metacompiling F83, to generate a new F83 with this change. CAPS ON and CAPS OFF The default condition for F83 words is that both upper case and lower case are considered the same. For example WORD and word are the same. If you prefer to treat upper case letters and lower case letters as different, set CAPS to false by typing CAPS OFF <CR>. CAPS ON <CR> will switch back to the original condition. 2.3 Standard System Documentation Requirement 1. The system dictionary space is CPU dependent and can be determined by typing HERE U. <CR> 2. The application dictionary space is also CPU dependent and is the difference between the top of the dictionary and the beginning of the parameter stack. The location of the parameter machine. The application dictionary space can be determined by typing SP@ HERE - U. <CR> 3. The data stack space is the same as the dictionary space. 4. The return stack space was arbitrarily set at 256 bytes. It can be altered by remeta-compiling the system. 5. No mass storage block ranges are reserved by the system, other than the contents of the files that are distributed. 6. The user has available to him blocks 0 thru 65534. Note that block 0 may not be used for loading. Block number 65535 is reserved to indicate the buffer is missing. 7. Any ASCII terminal should work with this system. If the user has a cursor addressable terminal, the editor can be easily modified to take advantage of the terminal's characteristics. System action taken upon error conditions: ' <name> ['] <name> not found results in ? error message */ */MOD / /MOD MOD UM/MOD all division by 0 errors result in a 0 quotient : in the case of an error, a ? error message will be printed DO if a nesting error occurs, the system will crash. (if you are lucky) 2.4 Version 2.0 General Information This Section describes most of the changes to F83 between versions 1.0 and 2.0. It is always difficult to follow a moving target. In the six months since we released version 1.0 we have received so many good suggestions that the temptation to use some of them was impossible to resist. To all of you who contributed, thank you again. We will try to avoid any further changes until 1985 at the earliest. If there are bugs, we will report them separately. Updating the various versions is a lot of work even without offering any support, and we are tired. It is time to move on to applications, and do something useful for a change. The changes were as follows: General: * Removed the superfluous NOOP from all self-defining words. * Changed all instances of C; to END-CODE ( by request). * Partitioned META into META.BLK ( the meta-compiler ) and KERNEL.BLK ( the source for the kernel ). META: * Fixed .SYMBOLS KERNEL: * Removed null from the system. Sealed search orders no longer require the old magic null word. * Fixed PARSE and PARSE-WORD. They used to increment >IN past the end of source text. * Changed CP/M to DOS. * Moved kernel DOS words into DOS vocabulary. * Added USER VARIABLE IN-FILE. All file operations read from IN-FILE and write to FILE. This allowed removing the confusing FILES vocabulary. User interface is unchanged: FROM <file> makes <file> the IN-FILE. OPEN <file> makes both the same. LOAD uses IN-FILE, then resets it to FILE. This is probably appropriate. * FBLOCK and FBUFFER take an fcb address and a block nuber. * SWITCH exchanges FILE and IN-FILE. * ?UPPERCASE conditionally forces a string to upper case. Used by DEFINED and FORGET. * EMIT primitives renamed: (CONSOLE) is console only, (EMIT) is for console and maybe also printer, depending on PRINTING. * Fixed CONTROL. * Made default (PRINT) not use LISTST, because it hangs on many systems. Optionally use LISTST if available for faster spooling. * Renamed FORTH control character table from CC1 to CC-FORTH. * Changed DO to ?DO in -TRAILING. * Deleted HEADER from CREATE, made CREATE do it all. * Changed ,VIEW to make file 0 if BLK is 0. * Added \S for comment to end of screen. * Added better error handling for disk reads and writes. * Accessing a BLOCK which is Out of Range no longer leaves the buffer assigned to the non-existent block. * Changed DISCARD to mark discarded buffer as empty. * .FILE and FILE? added to display file names. EXTEND: * Split ONLY into the ONLY operator and the ROOT vocabulary. * Removed OPEN-FILE from FILE: and added it to VIEW. * Added VIEWS which installs files into VIEW-FILES table. * Moved SET-DRIVE into EXTEND, changed it to use the BIOS to determine whether a drive is legal, and renamed it SELECT. * DRIVE? prints the current drive. * Added A: and B: which select drive A or B. * Added error control into MAKE, CLOSE, READ, and WRITE. CPU: * Added three words for decompiling DOES> words. * Renamed FIX to UNBUG. UTILITY: FORTH: * Added :: for immediate compilation. * VIEW is now wordier. It prints the file name and screen number of the source code for a word, then OPENs the file and LISTs the code. * Made SEARCH much faster when CASE is significant ( false), by SCANning for the first character. Turn CAPS OFF for speed. * Added .SCR which prints current screen number and file name. It is used by LIST and EDITOR .ALL. * Changed N and B to include DISK-ERROR OFF. EDITOR: * Changed ?TEXT to use PARSE instead of WORD. This allows commands like "F ^" to use the contents of the buffers. * Modified auto display updating to work correctly with both smart and dumb terminals. * Added FIX which VIEWs and EDITs. * Renamed JUST to J. I use it a LOT. * Made ED smarter: it does not change context if already editing. * ID field defaults to blanks, not nulls. * GET-ID waits for an extra character to allow you to read what you typed before hitting return. Showing: * SHOW now uses (SEMIT) which outputs to either the console or the printer, but not both, depending on PRINTING, which is reset by (ABORT"). * SHOW works for small files: PR replaces out-of-range blocks with LOGO. * FOOTING is vectored. * PAGE defaults to linefeeds. Many people did not have form-feed capability. Multitasker: * Renamed BACKGROUND to BACKGROUND: because it compiles until a semi-colon. NEW FILES: * HUFFMAN.BLK contains the source for the Huffman encoding used on the files as shipped. * CLOCK.BLK shows how to use a clock/calendar to automatically set the editor date stamp when you boot. The code is for a CompuPro System Support 1, but should give you some hints. * HUNT.BLK has source for HUNT. HUNT <sub> lists all words whose name contains the given substring. 2.5 Creating custom applications F83 allows precompilation of FORTH applications. Redirection of BOOT to the top level word then saving the executable image will generate a custom application. The following sequence will create a custom application. Using this technique you can generate a sealed application blocking the user from access to Forth. Test and debug your application the type the following. DECIMAL nn LOAD <CR> ( nn is your load screen number ) ' MY-PROGRAM IS BOOT <CR> ( execution starts with MY-PROGRAM on cold start ) SAVE-SYSTEM MY-FILE.COM <CR> ( saves the executable program, as MY-FILE.COM ) 2.6 Metacompiling F83 Metacompiling allows you to change word definitions or to eliminate unnecessary words from your application. You could even change the assembler definitions to cross compile a new FORTH system for a different processor or system. META86.BLK screens 25 through 45 provide the documentation on the Metacompiler source. The source code proves some information on how to use this facility. The following sequence will recompile a new F83.COM file. Put disk 2 in drive A and type the following. A>F83 META86.BLK <CR> When F83 boots type. 1 LOAD <CR> The Metacompiler will be compiled then KERNEL86.BLK will be compiled and you will get a string of screen numbers and two messages. When the kernel has completed compilation a summary of of system statistics will be printed on the screen. Instructions on what to do next follows the summary. Unresolved references: Statistics: Last Host Address: 35890 First Target Code Address: 38694 Last Target Code Address: 50216 Now return to the DOS and type: KERNEL EXTEND86.BLK <CR> OK <CR> Type BYE <CR> to exit to DOS. Copy KERNEL.COM to disk 1, put disk 1 in drive A and type the following. A>KERNEL EXTEND86.BLK <CR> OK <CR> You will get a progress message as compilation of each functional area starts to compile. The last two messages are. System has been loaded, Size = 26337 System saved as F83.COM ok Now type BYE <CR> to exit to DOS. Type F83 <CR> and test your new F83. 2.7 Quick Reference To be added later. 4.0 MSDOS services To be added later. Using DOS calls through BDOS you can use system functions or even run other programs from Forth. The assembler allows you to speed up any function that is too slow or to call assembly language subroutines. 7.0 Source Listings The source listings for the files listed below can be printed by entering F83 then using SHOW in the SHADOW vocabulary. The list of source files then the steps to list them follow. You need an Epson or IBM printer to get the source plus documentation screens on an 8 1/2 " X 11 " page. META86.BLK KERNEL86.BLK EXTEND86.BLK CPU8086.BLK UTILITY.BLK HUFFMAN.BLK EXPAND86.BLK (CLOCK.BLK) Put your working disk with F83.COM and META86.BLK in drive A:. Put your other working disk in drive B:. Turn on your printer then type the following lines as shown. A>F83 META86.BLK <CR> 0 21 SHADOW SHOW <CR> OPEN B:KERNEL86.BLK <CR> 0 92 SHOW <CR> B: OPEN EXTEND86.BLK <CR> 0 13 SHOW <CR> OPEN CPU8086.BLK <CR> 0 25 SHOW <CR> OPEN UTILITY.BLK <CR> 0 54 SHOW <CR> Put the master disk with HUFFMAN.BLK and EXPAND86.BLK in drive B: and type the following. OPEN HUFFMAN.BLK <CR> 0 21 SHOW <CR> OPEN EXPAND86.BLK <CR> Set your printer to top of form. PRINTING ON <CR> 0 2 TRIAD <CR> Set printer to top of form. 3 5 TRIAD <CR> PRINTING OFF <CR> Later: In the traditon of Forth, one programmer can make the whole thing much easier by codng an easy to use word. The word in this case is the command LISTING. LISTING lists the whole file to the printer by starting at screen zero and going to the CAPACITY of the file. Neat! 8.0 Forth Books The FORTH 83 Standard and other books on Forth can be purchased from several places three of which are listed below. FORTH Interest Group P. O. Box 1105 San Carlos, CA 94070 Phone: 415-962-8653 Mountain View Press P. O. Box 4656 Mountain View, CA 94040 Phone: 415-961-4103 Computer Literacy Book Store 530 Lawrence Expressway Santa Clara, CA 94086 Phone: 408-730-9955 Many other book stores carry the books recommended here and other books on Forth. Check with your favorite local book store. The F83 imp lementation follows the book STARTING FORTH by Leo Brodie. THINKING FORTH also by Leo Brodie is good too. INSIDE F83 by C.H.Ting is good reference book. It is published by Offete Enterprises, 1306 So. B. St, San Mateo, CA 94402 name and screen number of the source code for a word, then OPENs the file and