CP/M

home *** CD-ROM | disk | FTP | other *** search

/ CP/M / CPM_CDROM.iso / lambda / soundpot / f / figforth.lbr / FORTH.DZC / FORTH.DOC

Wrap

Text File | 1993-10-26 | 11.3 KB | 264 lines

This documentation describes the extensions to FORTH which make up KFORTH. If you are not familiar with the FORTH language you will need to get a book to describe the structure, syntax, and vocabulary of the language. A very popular beginning FORTH book is: Starting FORTH By Leo Brodie Prentice-Hall 1981 The book will teach you the basics of FORTH. This documentation provides you with the information to use this version of FORTH which we call KFORTH. A Few Words About Forth To start FORTH you run the KFORTH.COM file just as any other .COM file by typing KFORTH <carriage return>. To get out of FORTH type BYE <CR>. FORTH does not create or use standard CP/M files as you are used to seeing. In FORTH the "file" you work with is called a screen. KFORTH provides you with 150 screens per disk which are kept within a 150 K CP/M file called FORTH.SCR. This allows you to put CP/M files on the remainder of the disk without getting into your FORTH workspace. It is possible to create a file FORTH.SCR which is less than 150 K. You should avoid this since KFORTH expects to have the full 150 K available and will try to read your CP/M files as if they were a FORTH screen. It is easy to avoid this by creating a screen or having a FORTH.SCR file on the disk with KFORTH.COM. To create a 150 K FORTH.SCR on a blank, formatted disk use the FORTH extension MAKE-NEW described below. Or you can use an existing FORTH.SCR like the one on this disk. The way you get into trouble is when you run KFORTH.COM on a disk that has no FORTH.SCR or use the FORTH extension BACK-UP-DISK (described below) without have an empty FORTH.SCR in drive B. In either of these cases, KFORTH just builds a file FORTH.SCR but only reserves the blocks it needs. Then if you PIP CP/M files onto that disk they may fill in the unreserved blocks. The next time you use KFORTH, it expects to be able to use all of its 150 K workspace even though it never reserved it. If you LIST a screen that has a CP/M file residing in its place, well, thats when things get weird. It is also a good idea if you are new at FORTH, not to put a disk in drive B with CP/M files on it unless there is a FORTH.SCR on it as well. _____________________________________________________________________________ FORTH.COM-------------------------------------------------------------------- This is the fig-FORTH kernel. It was written in assembly language and provides the interpreting core to make it possible to write in FORTH. In addition to the source for the kernel we will also include any extensions to our KFORTH that are submitted as they come in (or until the disk is full). FORTH.COM is the core of KFORTH.COM. You may extend the FORTH.COM to become KFORTH.COM by using the FORTH screens on this disk in the file FORTH.SCR. To do this use PIP to transfer FORTH.COM and FORTH.SCR to another disk (blank and formatted). Then use SYSGEN.COM to put your system tracks on this disk as well. Now place this disk in drive A and hit the reset button. Once you get the system prompt ( A> ), type in FORTH and a carriage return. FORTH will ask you for the date and you may respond or answer with a carriage return. Then type in 50 LOAD (must be uppercase) and a carriage return. This will cause FORTH to load into memory an executable version of the extensions. It will display the first line of each screen that it loads. After it has loaded about half of the extensions it will type to the screen: ENTER YOUR INITIALS IN THREE LETTERS and wait for you to do so. This will customize your editor so that it will put your initials on the first line of the FORTH screen whenever you edit. After you do this FORTH will load the rest of the extensions. Finally FORTH will return control to you and give you the OK prompt. Exit FORTH by entering: BYE<carriage return> Forth will then respond with: Forth is 61 Records Long LEAVING FORTH Have A Nice Day The number of records is the number of 256 byte pages of memory that FORTH now occupies with all of its extensions. But the extended version of FORTH is still in memory! To save it on disk as a .COM file you must now enter: SAVE 61 KFORTH.COM<carriage return> You now have a file on that disk which is identical to KFORTH.COM on this distribution disk but now it will leave your initials in a screen that you edit instead of BOB. _____________________________________________________________________________ FORTH.SCR-------------------------------------------------------------------- This file contains the screens that have the source for the FORTH extensions. Some of the extensions are in the vocabulary of KFORTH and others have to be LOADed before they may be used. First lets look at the "built-in" extensions. STATUS The line of text at the top of the CRT when you are in KFORTH is due to this extension. STATUS shows you the contents of the stack, the number base you are working in, and the vocabulary you are working in. Screen 16. WHERE This extension will find an error in compilation and underline it. Screen 17. OOPS ERR ERR replaces the standard FORTH word ERROR and uses WHERE to find and underline a mistake. OOPS puts you in the EDITOR and positions the cursor at the mistake. Screen 18. PATCH This extension allows you to redefine a word without having to re-compile. Puts a call to the new word at the beginning of the old word. Screen 13. CP/M This extension has some utilities to allow you to make a CP/M file on disk B. Screens 25-27. SCREEN-ORIENTED EDITOR The screen editor is loaded into the KFORTH vocabulary. It is very easy to use once you get started. The source for this editor is in screens 61-97. To use the screen editor you enter the number of the screen you wish to edit followed by an E. For example 100 E will edit screen 100 (empty on this disk) If you enter that when you are in KFORTH it will display it on the screen after it pulls it from the disk. You are now in the editor. A ^Q will display the HELP screen which shows you the keypad usage map. The cursor control (arrow) keys will move you about the screen and you may edit text as you please. To exit either choose exit with no update of the disk file or exit and write to disk (^Q to see the HELP screen). After you exit the editor the screen will not be written out to disk until you (or a FORTH utility) FLUSH the buffer. (Enter FLUSH just to make sure). If you did the editor customization above the next time you view the screen you just edited your initials and today's date should be on the first line of the screen. The editor also has some FORTH words to re-direct the output while you are in FORTH. These are: PRINTER-ENABLE -- send the output to the printer instead of the CRT CRT-ENABLE -- un-does the above (output goes to CRT) BOTH-ENABLE -- output to printer and CRT PRINTER-EMIT -- same as EMIT but to printer BOTH-EMIT -- EMIT to CRT and printer The ASSEMBLER The assembler is an 8080 assembler and is on screens 108-114. This allows you to enter and include 8080 mnemonics in your FORTH programs. The assembler works as a standard FORTH assembler does. All code entry must be in reverse polish notation. The code segment should start with the FORTH word CODE and end with C; (another FORTH word). An example segment would be: CODE BOP H POP, H PUSH, H PUSH, H PUSH, NEXT, C; ^ ^ ^ ^ ^ ^ ^ ^ | | | | | | | |___________end code segment | | | | | | |___________return to interpreter | | | | | |________________push H and L registers | | | | |________________________push H and L registers | | | |________________________________push H and L registers | | |________________________________________pop H and L registers | |_________________________________________name for this code segment |_____________________________________________________begin code segment This section of code (BOP by name) duplicates the top stack item twice. To test this in KFORTH enter the line above (don't forget the commas after the instructions). The assembler will create the word BOP and put it in your dictionary (type VLIST to confirm this). Then put a number on the stack (by typing the number and a carriage return) and then type BOP. Look at the contents of your stack. The number you entered should now be there three times. DECOMPILER The decompiler source is in screens 102-106. It allows you to decompile FORTH words that you do not have the source for. As an example you could decompile the FORTH word LIST. To do this you would enter: GOESINTO LIST <carriage return> Now each time you hit the space bar you will get the next FORTH word used by LIST. If you see one of these FORTH words (say PAGE) and want to decompile it you may hit the carriage return and the decompiler will work on that word, showing you the lower FORTH words that make up that word. To exit the decompiling session just hit the space bar until the decompilation is complete. NUMBER-BASE When KFORTH begins the number base is set to DECIMAL. You may choose three other bases to use, HEX, BINARY, or OCTAL. Entering any of these words will change the number base you are working in. The base you are presently in is displayed at the top of the screen by STATUS. _____________________________________________________________________________ Extensions Which Are Not Loaded Into KFORTH.COM------------------------------ There are some other FORTH extensions in these screens that are not loaded to become part of the KFORTH.COM file. To use these utilities you must load them into memory by using the LOAD command. To do this type in the number of the screen where it is located followed by a space and the word LOAD. Then you may type in the FORTH word and it will execute. Screen #32 LOG This word will copy what is on the CRT into a CP/M file on drive B called FORTH.LOG. It will begin copying when you type START-LOG and stop when you type END-LOG. It does not terminate lines with a carriage return/ line feed, only a carriage return. If you would want to make a file record of the words in your FORTH dictionary enter: 32 LOAD START-LOG VLIST END-LOG Screen #33 BACK-UP-DISK This word will copy any screen with something written in the first line to drive B. Backs up all screens. You should have a FORTH.SCR with all screens empty in drive B. To use enter: 33 LOAD BACK-UP-DISK Screen #34 TRIAD-THRU Use this word to list screens in groups of three followed by a form-feed. If you want it to go to the printer, don't forget to type PRINTER-ENABLE first. You need to type a beginning screen # and an ending screen #. To list screens 30-35 to the printer enter: 34 LOAD PRINTER-ENABLE 30 35 TRIAD-THRU Screen #40 MAKE-NEW This constructs the CP/M file FORTH.SCR with empty screens. Place a blank formatted disk in drive B and enter: 40 LOAD MAKE-NEW Do this before using BACK-UP-DISK or any time you need a new FORTH workspace. Place KFORTH.COM on a disk with this new FORTH.SCR and start FORTH with a new slate.