MESA FORTH for Atari 8Bit Handbook#

Chapter 1#


MesaForth is based on the 6502 fig-Forth model. The major difference from the model is in the size of the screen on disk (512 bytes instead of 1024 bytes). You should refer to fig-Forth documentation for a complete description of Forth and the standard words provided in fig-Forth. This document will describe the special features provided in MesaForth.

A major difference between MesaForth and other Forth's available for ATARI is that MesaForth runs under ATARI DOS 2.0S. Forth source files and data files are written on standard DOS formatted diskettes. This means that Forth files can be interchanged with any other program that uses DOS files (ATARI BASIC, Assembler/Editor, Music Composer, ATARI Word Processor, etc.). This can make MesaForth a powerful tool in producing efficient software on your ATARI.

Your MesaForth system diskette contains more than the fig-Forth model. It also contains some additional software:

  1. Complete CIO interface to ATARI Operating System and DOS
  2. Support of Graphics/Sound/Joystick routines in O.S.
  3. Complete support of character string manipulation
  4. Interface to Disk Handler routines in O.S.
  5. Screen editor for modification of Forth files
  6. Text formatter for use with on-line documentation
  7. Turnkey support to create application programs

Chapter 2#

Booting MesaForth#

Before you use your MesaForth disk for the first time, you should make sure it is write-protected so that you can't accidentally destroy it. It is suggested that you duplicate this disk and store the original and use it only as a master disk. You should use another disk when you are running MesaForth. To boot MesaForth, follow these steps:

  1. Turn on disk drive and insert MesaForth diskette
  2. Turn on any other peripherals
  3. Turn on computer

DOS will boot up first. It will execute the AUTORUN.SYS file on the system disk. This will load and execute files with extensions of .IN0, .IN1, .IN2, .IN3, and .IN4 until it finds no files with these extensions. If you have an Interface Module (850), you will need the file INTRFACE.IN0 on your system disk. If you have any other special boot files, they should be loaded next. Then the MesaForth object file will be loaded and executed last (FORTH.IN1 on standard system disk). You will then see a message (fig-FORTH x.x) which announces that you are now in Forth.

At this point, you can enter any existing Forth word or enter a colon definition.

Defining system words#

When you first boot up your MesaForth, you will have the minimum subset of Forth words defined. Before you can do anything else, you will probably need to add the system extensions. These words are contained in the SYSTEM.4TH file. This file also contains in screens 4 through 6 the system error messages (you should usually leave DR0 selected to SYSTEM.4TH). This file defines some useful extensions to Forth such as character string manipulation and the :SELECT word. These will be described later.

To load these words, type:


MesaForth will then go out to the disk and load the words from SYSTEM.4TH.

After it is finished loading, it will type OK. This indicates that it is finished with the previous command(s) and is ready to accept new instructions.

Defining the screen editor words#

Now that you have loaded the system words, you can load the MesaForth editor. To do this, type:


This will select EDITOR.4TH as DR1 and execute a LOAD for that file.

Defining the DOS words#

Often you will want to perform some standard DOS operations on your disk. You can do these by loading the DOS words. This can be done by typing:


This will load the words from DOS.4TH. The words available will allow you to do directories, deletes, renames, locks, unlocks, and some copying. These words are designed to be forgotten when you are finished with them. This will release the memory used by these functions so that you can use it for you program. To forget DOS, type:


Chapter 3#

MesaForth file format#

Some differences have been made in the Forth file structure in MesaForth. First, the screen size has been modified to 512 bytes. This change is primarily due to the problem of displaying an entire Forth screen at one time. Fig-Forth suggests using a screen size of 1024 bytes (16 lines of 64 characters each). Since the ATARI line width is at most 40 characters, using 64 character lines would cause some confusion. In MesaForth, the line size is 32 characters. Each screen still has 16 lines, producing a screen size of 512 bytes.

Another major change is having Forth run under the ATARI DOS. Using DOS gives you access to files used by other ATARI DOS-supported programs. But, running under DOS adds some additional changes to Forth. First, DOS must be booted before Forth. DOS requires some memory; you lose this memory for use by your Forth programs. Also, Forth usually performs random accesses to screens on disk. But under ATARI DOS, files are normally accessed sequentially. MesaForth will simulate the random access, by creating an internal screen list showing the position of each screen within an ATARI file. After the list has been made (it is made automatically), then accesses to individual screens will be very fast (random access).

Note that since MesaForth supports all CIO functions, including the DOS file accesses, you will normally use Forth files for only your Forth sources (word definitions). Data files will usually by normal DOS files.

Chapter 4#

Character strings#

A useful extension to Forth in MesaForth is the support of character string operations. Since Forth is stack-oriented for its numeric operations, it is natural to add character string words as stack-oriented operations. A special string stack is set up separate from the numeric stack. It has its own stack pointer ($SP). The size of the string stack is defined by the variable

  • $*. The string stack and words are established when you load
SYSTEM.4TH. You can change the size of the stack, or change/add words by changing SYSTEM.4TH.

Refer to Appendix A for a complete list of the string operations. For efficiency, no special checks are performed on the string stack. If you exceed its size, or pop too many elements off of the string stack, your program will probably crash. Remember, you can add these checks by modifying the words in SYSTEM.4TH. The following sections will describe the string operations provided in MesaForth.

Stack Manipulaton#

" text"               ( -$> $ )

This operation pushes a quoted text string on top of the string stack. The string must be terminated by a double quote ("). NOTE that there "must" be a space between the first quote mark (") and the first character in the text string. Examples:

" This is a text string"
""                    ( -$> $ )

This word pushes an empty (zero-length) string on top of the string stack.

$DROP                 ( $2 $1 -$> $2 )

This is like the DROP word, except it drops the top string off the string stack.

$DUP                  ( $1 -$> $1 $1 )

This is like the DUP word, except that it duplicates the top string on the stack.

$FILL                 ( n c --> ) ( -$> $ )

This operation, takes the number of characters (n) and the character (c) off the numeric stack, and produces a string at the top of the string stack which contains the indicated number of characters c. Example:


This will put a string of 20 blanks on top of the string stack.

$SWAP                 ( $1 $2 -$> $2 $1 )

Just like the SWAP word, except that it swaps the top two strings on the string stack.

String operations#

$+                    ( $1 $2 -$> $1+$2 )

This operation is similar to the + word; it concatenates the top string on the stack onto the end of the second string on the string stack. Example:

" a" " b" $+
( this produces "ab" on the string stack )

$.                    ( $ -$> )

This prints the top string on the string stack.

$<                    ( --> f )  ( $1 $2 -$> )

This operation compares the top two string on the string stack. If $1 is less than $2, then the result (f) will be true(non-zero), otherwise the result will be false (zero).

$=                    ( --> f )  ( $1 $2 -$> )

Similar to $<, except the result will be true if $1 is equal to $2.

$COMPARE              ( --> n )  ( $1 $2 -$> )

This word is the internal comparison function. It is called by $< and $= to perform the actual comparison. It compares the top two strings on the string stack and returns -1 if $1<$2, 0 if $1=$2, and 1 if $1>$2.

$FETCH        ( addr len --> )  ( -$> $ )

This word is used to fetch strings not stored in string variables. It takes a string starting at the address (addr), and pushes it on top of the string stack. Its length will len.

$LEN           ( --> n )

This returns the length of the top string on the string stack.

$P!             ( --> )

This word resets the string stack pointer (makes the string stack empty). This is automatically done whenever a warm-restart (or cold-start) is performed. You can also do this yourself anytime, but be warned that anything that was on the string stack will be lost.

$P@            ( --> n )

This word returns the value of the string stack pointer (which is pointing to the address of the top string on the string stack).

  • NOTE* that you will probably never need to use this word since all
of the string operations can be performed without knowing the address of the string stack. This word is used in defining the string operations like $DROP or $SWAP.
$P2             ( --> n )

This word returns the address of the second string on the string stack. *NOTE* that you will probably never need this word. It is used to define other string operations.

$STORE          ( addr max --> actlen )    ( $ -$> )

This word is used to store strings into non-string variable locations. The top string on the string stack is stored into memory at the address (addr). The maximum string size allowed for storage is max. This word will return the actual length of the data stored on top of the numeric stack (actlen).

$VARIABLE xxx                   ( len --> )

Similar to the VARIABLE word, except that the numeric value on top of the stack indicates how many characters to allocate to the string variable. This will limit the size of the string which may be stored in the string variable. But it does not mean that all strings need to be this size. The actual length is also kept for each string variable. Example:

              10 VARIABLE NAME ( define 10 character string variable
                                 called NAME )
              " Smith" NAME $! ( store 5 character string in NAME )
              NAME $VARLEN     ( this will return 5, since the actual
                                 length is only 5 )
              " Smith, Jonathan" ( this will only store the leftmost 10
                                   characters into NAME, since its max
                                   length is 10 )
$VARLEN                         ( vaddr --> len )

Returns the actual length of the string variable (vaddr).

$VARMAX                         ( vaddr --> max )

Returns the maximum length of the string variable (vaddr).

Chapter 5#

MesaForth Editor#

You will be using the MesaForth Editor to create and modify your Forth source files. This editor is a screen editor; it allows you to make changes to your source by using the cursor controls and making changes by typing on the screen without using special editing commands. The screen editor is similar to the functions provided by ATARI BASIC or the Assembler/Editor.

To use the editor on a source file, you must first select the file you wish to edit. This can be done using the $SETDR1 word.

For example:


This will look for the file FILE.4TH on D1:. It will be used as DR1. DR1 is then selected as the active file. Now to invoke the editor, you use a special word:

EDIT                  ( screen --> )

This word invokes the editor on the indicated screen in the currently active file (DR0 or DR1). The television display will be cleared and the Forth screen will be displayed. All 16 lines of the screen will be shown, with a box around it (so that you can tell what is part of the screen, and what is information shown by the editor. The bottom of the display will show what special editor commands are available.

Standard editing commands:#

While you are in the editor, any character you type (except special control characters) while be entered into the screen at the current position of the cursor. It will replace whatever was in that position of the screen. The editor control characters are:

  • arrows*

The arrows (control characters left of the RETURN key) will move the cursor the appropriate direction in the screen.


This key will delete the character preceeding the cursor in the screen.


Holding the shift key down while hitting the DELETE/BACK-SPACE key will cause the entire line on which the cursor is positioned to be deleted. All lines below it on the screen will move up to fill in.


Holding the shift key down while hitting the INSERT key will insert a blank line at the line on which the cursor is positioned. All lines (including the line currently holding the cursor) will move down. Note that the last line in the screen will be moved outside of the screen. The editor will hold that line for you in case you accidentally inserted a line. To restore the screen to its original state, delete the line you just inserted.


Holding the ctrl key down while hitting the DELETE/BACK-SPACE key will delete the character currently under the cursor in the screen.


Holding the ctrl key down while hitting the INSERT key will cause a space to be inserted at the cursor. All characters after the cursor (including the character under the cursor) will shift right one position. The editor will not allow you to shift a character off the end of the line. You will have to split the line up if it gets full and you still need to add something to it.

Special Editing commands#

There are some additional editing commands available. To enter these commands, first hit the ESCAPE key. Then enter one of the following commands:

  • X* (eXit)

This command saves all of the screens that have been edited, and exits the editor mode, returning you to normal Forth command mode. You must enter this command before leaving the editor. Otherwise not all of the screens you have updated will get flushed to the disk.

  • A* (Abort)

This command aborts editing of the current screen. It will save all of the other screens that have been updated though.

  • C* (Copy)

This command allows you to move screens around within your file. It will ask you for the starting and ending screen numbers to be moved. It will also you ask you for the number of the first target screen. Enter each of these numbers, hitting a RETURN after each.

  • E* (Erase)

This command erases the current screen. It fills the entire screen with blanks.

  • S* (Search)

This command is not yet implemented, it would be a search through the file for a particular string of characters.

< (preceeding screen)

Use this command to move to the preceeding screen in the file.

> (following screen)

Use this command to move to the next screen in the file.

  • number* (move directly to a screen)

After hitting the ESCAPE key, enter a number, then a RETURN. The EDITOR will move directly to that screen.

Chapter 6#

ATARI Input/Outputy#

MesaForth provides a complete set of Forth extensions interfacing to the ATARI Operating System. The Input/Output (I/O) words fall into the following categories:

  1. Central Input/Output (CIO)
  2. Disk Handler
  3. Disk Operating System (DOS)
  4. Special I/O (sound, graphics, joysticks)

Refer to Appendix A for a complete summary of these functions. The remainder of this chapter will give a brief description of the features provided in MesaForth.

CIO functions#

The interface to CIO provides both input and output similar to what is available in ATARI BASIC. The ATARI Operating System allows up to 8 files/devices to be operated at a time. They are identified by individual I/O Control Blocks (IOCB). These IOCB's are identified by #0, #1, ... #7. MesaForth and the ATARI O.S. use some of these internally. The IOCB's available for your use are #0, #3, #4, #5, and #6. These words are defined for you convenience.

The functions provided are:

CLOSE close file/device
GET get character(byte)
GETBUF get buffer from file/device
GETREC get record (terminated by End-Of-Line)
JSRCIO call CIO (assumes IOCB set-up)
NOTE note position in disk file
OPEN open file/device
POINT point to position in disk file
PUT write character(byte)
PUTBUF write buffer to file/device
PUTREC write record (terminated by End-Of-Line)
STATUS return status of file/device
XIO call CIO (like BASIC XIO)

For a detailed description of OPEN, CLOSE, NOTE, POINT, and XIO refer to the ATARI BASIC manual. The calling sequence and meaning of arguments is similar, with the exception of the file name arguments. The ATARI O.S. requires that file name be terminated by an EOL. A special string function is provided ($FILE) which converts the top string on the string stack into a file name, and returns the address of the name on the top of the numeric stack. You can use this address in OPEN (or XIO). Then use a $DROP to drop the file name from the string stack. Example:

#3 GET

The above example opens D:FILE and gets the first byte from the file. The file is then closed. Another word (?DISKERROR) can be used to abort your program if a disk error occurs.

Disk Handler#

The disk handler words interface to the ATARI O.S. disk handler routines. They support reading and writing of individual sectors on a disk (without using the DOS). Two extra words are defined which will dump sectors from disk, and do a sector by sector copy of a disk.

DOS Functions#

Some of the DOS functions are supported in MesaForth. You can delete, lock, rename, and unlock files. You can also do a directory of your disks. These functions use the string stack for the name of the file(s). For example:

" D:*.*" DIR

An additional function (SCRCOPY) can be used to create a copy of the currently selected file (DR0/DR1).

Special I/O#

Words have been defined to access the sound, graphics, and joystick functions provided by the ATARI O.S. These words are similar to the ATARI BASIC commands providing the same features:

COLOR selects color
DR. draws line (DRAWTO)
GR. opens screen for graphics (GRAPHICS)
LOC. locates color at point (LOCATE)
PL. plots point (PLOT)
POS. positions graphics cursor (POSITION)
SE. sets color register (SETCOLOR)
SO. sets voice for sound (SOUND)
STICK tests joystick position
STRIG tests joystick trigger

An additional word (CVTSTK) has been provided to convert the joystick position values to something more meaningful.

Chapter 7#

Miscellaneous Functions#

MesaForth provides two additional features useful for creating turnkey applications in Forth. A text formatter is provided to support on-line documentation to the screen or to a printer. A TURNKEY word is provided to save a set of loaded Forth words. A NEW-ABORT word allows you to chain your own functions into the warm restart sequence (SYSTEM RESET).

The Text Formatter reads a file generated using the MesaForth Editor (i.e., a Forth file of screens with no carriage returns). It looks for a small set of commands starting in column 1 of a line:

.BREAK pause on screen (so it can be read)
.CENTER text center text on line
.END end of file
.FILL begin filling of text (right-margin justify)
.NOFILL end filling of text
.PAGE force a start of a new page (clear screen)
. force a blank line

Use the text formatter to generate instructions for programs you have written. You call the text formatter (after it is loaded) by using the FORMAT word. It will display the text on the screen or print it on a printer. It will stop formatting if the BREAK key is hit.

To save your own turnkey programs, use the TURNKEY word. It will save the currently loaded Forth words to a binary file on disk. Usually you will have a blank disk (formatted, with DOS).

You will use TURNKEY to save your Forth program as AUTORUN.SYS. TURNKEY sets the fence so that your words cannot be deleted when you load the new file. Example:


A useful feature is to create programs that can be run, but that can be set so that the user cannot enter Forth to see what you are doing. This can be done by using the NEW-ABORT word. To automatically call one of your words when the SYSTEM RESET key is hit (or when the program is first loaded), define the following word:

: START  NEW-ABORT  yourword ;

The START word will automatically be executed whenever Forth restarts (on SYSTEM RESET or initial load). This can be used to prevent someone from ever getting into Forth. It can also be used to reset some application specific feature (like the string stack).

Appendix A -- MesaForth Reference#

The following reference table describes all of the Forth words available on the Forth system disk. This version of the Forth Interest Group Forth (figFORTH) is based on Forth 78. The difference (from figFORTH) is the block and screen size (512 bytes). Some of the words are defined in the standard Forth object file, others are defined in Forth source files on the system disk and can be modified and loaded.

The first column contains the name of the word.

The second column describes the stack operation:

( input --> output )
( $input -$> $output )

The normal stack is described with -->, the string stack is described by -$>. The top of the stack is the rightmost item in a list. The input items reflect the stack before the word is executed. The output items indicate the stack state after the word is executed. The operands are defined as follows:

n, n1, ... 16-bit signed integer numbers
d, d1, ... 32-bit signed integer numbers
u 16-bit unsigned integer number
addr 16-bit address
b 8-bit byte
c 8-bit ATASCII character
f boolean flag (0 is false)
iocb offset of I/O control block (i.e., hex 00, 10, 20, ...)

The third column indicates the source of the word. The values for this column are:

fig fig-Forth word in normal Forth object file
ext MesaForth extensions in Forth object file
SYS in SYSTEM.4TH, words usually needed
DISK in DISK.4TH, disk handler interface
EDIT in EDIT.4TH, Forth screen editor
FORM in FORMAT.4TH, text-formatting words for use in program HELP files
TURN in TURNKEY.4TH, saves current Forth words for turnkey operation

Stack Manipulation#

-DUP ( n --> n ? ) figDuplicate only if non-zero
>R ( n --> ) figMove top item to "return stack" for temporary storage (use caution)
DUP ( n --> n n ) figDuplicate top of stack
DROP ( n --> ) figThrow away top of stack
OVER ( n1 n2 --> n1 n2 n1 ) figMake copy of second item on top
PICK ( nm...n1 --> nm...n1 nm ) extPick the mth item into the stack and copy it to the top of the stack
R> ( --> n ) figRetrieve item from return stack
R ( --> n ) figCopy top of return stack onto stack
ROT ( n1 n2 n3 --> n2 n3 n1 ) figRotate third item to top
SWAP ( n1 n2 --> n2 n1 ) figReverse top two stack items

Number Bases#

BASE ( --> addr ) figSystem variable containing number base.
DECIMAL ( --> ) figSet decimal base.
HEX ( --> ) figSet hexadecimal base.

Arithmetic and Logical#

* ( n1 n2 --> prod ) figMultiply.
*/ ( n1 n2 n3 --> quot ) figMultiply, then divide (n1*n2/n3), using double-precision intermediate.
*/MOD ( n1 n2 n3 --> rem quot ) figMultiply, then divide (n1*n2/n3), using double-precision intermediate.
+ ( n1 n2 --> sum ) figAdd.
- ( n1 n2 --> diff ) figSubtract (n1-n2).
/ ( n1 n2 --> quot ) figDivide (n1/n2).
/MOD ( n1 n2 --> rem quot ) figDivide (n1/n2), giving both remainder and quotient.
1+ ( n --> n+1 ) figIncrement number by 1.
2+ ( n --> n+2 ) figIncrement number by 2.
ABS ( n --> absolute ) figAbsolute value of n.
AND ( n1 n2 --> and ) figLogical AND (bitwise).
D+ ( d1 d2 --> sum ) figAdd double-precision numbers.
D+- ( d1 n --> d2 ) figApply the sign of n to d1, leaving it as d2.
DABS ( d --> absolute ) figAbsolute value of double precision number.
DMINUS ( d --> -d ) figChange sign of double-precision number.
M* ( n1 n2 --> d ) figMultiplies two numbers, producing a double-precision number.
M/ ( d n1 --> rem quot ) figDivide double precision number by single precision number, producing single-precision numbers.
M/MOD ( ud1 u2 --> u3 ud4 ) figUnsigned divide of double-precision number, producing single precision remainder(u3) and double-precision quotient(ud4).
MAX ( n1 n2 --> max ) figMaximum of n1 and n2.
MIN ( n1 n2 --> min ) figMinimum of n1 and n2.
MINUS ( n --> -n ) figChange sign of number.
MOD ( n1 n2 --> rem ) figModulo (i.e. remainder of n1/n2).
OR ( n1 n2 --> or ) figLogical OR (bitwise).
U* ( u1 u2 --> ud ) figUnsigned multiplication of two numbers, producing unsigned double-precision number.
U/ ( ud u1 --> u2 u3 ) figUnsigned divide of double-precision number by single-precision number, producing unsigned remainder (u2) and quotient (u3)
XOR ( n1 n2 --> xor ) figLogical exclusive OR (bitwise).


0< ( n --> f ) figTrue if number is negative.
0= ( n --> f ) figTrue if top number zero (i.e., reverses truth value).
< ( n1 n2 --> f ) figTrue if n1 less than n2.
= ( n1 n2 --> f ) figTrue if n1 equals n2.
> ( n1 n2 --> f ) figTrue if n1 greater than n2.


! ( n addr --> ) figStore word value at address in memory.
+! ( n addr --> ) figAdd number to value of word at address in memory.
<CMOVE ( from to n --> ) SYSLike CMOVE, except bytes moved starting at high address first.
? ( addr --> ) figPrint numeric value of word at address in memory.
@ ( addr --> n ) figFetch one word from memory at indicated address.
BLANKS ( addr u --> ) figFill u bytes in memory with blanks.
C! ( b addr --> ) figStore byte value at address in memory.
C@ ( addr --> b ) figFetch one byte at address from memory.
CMOVE ( from to u --> ) figMove u bytes in memory.
ERASE ( addr u --> ) figFill u bytes in memory with zeroes.
FILL ( addr u b --> ) figFill u bytes in memory with a byte value.

Control Structures#

BEGIN ...UNTIL until: ( f --> ) figLoop back to BEGIN until true at UNTIL.
BEGIN ...REPEAT while: ( f --> ) figLoop while true at WHILE. ...WHILE.
DO...+LOOP do: ( end+1 start --> ) +loop: ( n--> ) figLike DO...LOOP, except adds stack value to index at end of loop.
DO...LOOP do: ( end+1 start --> ) figSet up loop, given index range.
I ( --> index ) figPlace current index value on stack.
IF...(true) ...ENDIF if: ( f --> ) figIf top of stack is true (non-zero), execute.
IF...(true) ELSE...(false) ...ENDIF if: ( f --> ) figLike IF...ENDIF, except if false, the ELSE clause is executed.
LEAVE ( --> ) figTerminate loop at next LOOP or +LOOP.

Terminal Input-Output#

. ( n --> ) figPrint number.
." ( --> ) figPrint message (terminated by ").
.R ( n fieldwidth --> ) figPrint number, right-justified in field.
?TERMINAL ( --> f ) figTrue if terminal break request present.
BELL ( --> ) SYSRing console bell.
BL ( --> n ) figLeaves the .ATASCII. value of blank on the stack.
COUNT ( addr --> addr+1 u ) figChange length-byte string to TYPE form.
CR ( --> ) figDo a carriage return.
D. ( d --> ) figPrint double-precision number.
D.R ( d fieldwidth --> ) figPrint double-precision number, right-justified in field.
DUMP ( addr u --> ) SYSDump u .bytes. starting at address.
EMIT ( c --> ) figType character c.
EXPECT ( addr n --> ) figRead n characters (or until a carriage return) from input to address.
KEY ( --> c ) figRead key, put .ATASCII. value on stack.
PR-OFF ( --> ) SYSTurn the printer off (for terminal I/O).
PR-ON ( --> ) SYSTurn the printer on (for terminal I/O). All output from TYPE, EMIT, etc. will appear on the screen and the printer. All keyboard input will also be echoed on the printer.
SPACE ( --> ) figType a space.
SPACES ( n --> ) figType n spaces.
SPEMIT ( c --> ) SYSAllows special characters to be sent to the screen.
TYPE ( addr u --> ) figType string of u characters starting at address.
U. ( u --> ) SYSType the unsigned number.
WORD ( c --> ) figRead one word from input stream, stopping at character c (usually blank).

Input-Output Formatting#

# ( d --> d ) figConvert next digit of double-precision number and add character to output string.
#> ( d --> addr u ) figTerminate output string (ready for TYPE).
#S ( d --> 0 0 ) figConvert all significant digits of double-precision number to output string.
<# ( --> ) figStart output string.
HOLD ( c --> ) figInsert .ATASCII. character into output string.
NUMBER ( addr - d ) figConvert string at address to double-precision number.
SIGN ( n d --> d ) figInsert sign of n into output string.

Disk Handling#

B/BUF ( --> n ) FIGSystem constant giving disk block size in bytes
B/SCR ( --> n ) FIGSystem constant giving blocks per editing screen
BLK ( --> addr ) FIGSystem variable containing current block number
BLOCK ( block --> addr ) FIGRead disk block to memory address
DR0 ( --> ) FIGSelects use of .file. 0 for LIST, LOAD, and .EDIT.
DR1 ( --> ) FIGSelects use of .file. 1 for LIST, LOAD, and .EDIT.
EMPTY-BUFFERS ( --> ) FIGErase all buffers
FLUSH ( --> ) FIGWrite all updated buffers to disk
INDEX ( from to --> ) FIGLists the first line of the screens indicated
LIST ( screen --> ) FIGList a disk screen (.512 bytes.)
LOAD ( screen --> ) FIGLoad disk screen (compile or execute)
PLIST ( strt end --> ) SYSList the screens from strt to end to the printer (and screen)
SCR ( --> addr ) FIGSystem variable containing current screen number
UPDATE ( --> ) FIGMark last buffer accessed as updated

Defining Words#

: xxx f pointer to context vocabulary (searched first)
CURRENT ( --> addr ) FIGReturns address of pointer to current vocabulary (where new definitions are put)
FORTH ( --> ) FIGMain Forth vocabulary (execution of FORTH sets CONTEXT vocabulary)
VLIST ( --> ) FIGPrint names of all words in CONTEXT vocabulary
VOCABULARY ( --> ) FIGCreate new vocabulary named xxx

Miscellaneous and System#

' xxx ( --> addr ) FIGFind address of xxx in dictionary; if used in definition, compile address
( ( --> ) FIGBegin comment, terminated by right paren on same line; space after (
, ( n --> ) FIGCompile a number into the dictionary
ABORT ( --> ) FIGError termination of operation
ADDBLKS ( 0/1 n --> ) EDITAdds n blocks (screens) to the end of DR0(0) or DR1(1)
ALLOT ( --> ) FIGLeave a gap of n bytes in the dictionary
COLD ( --> ) FIGPerforms a system cold start (erases application program and restarts)
EDIT ( n --> ) EDITEnters screen editor for screen n of the current file (DR0/DR1)
FORGET xxx ( --> ) FIGForget all definitions back to and including xxx
FORMAT ( filespec -$> ) FORMRead the file, and format the text on the screen or printer
FREE ( --> n ) SYSReturns the number of free bytes left in memory
HERE ( --> addr ) FIGReturns address of next unused byte in the dictionary
IN ( --> addr ) FIGSystem variable containing offset into input buffer (used by WORD)
NEW-ABORT ( --> ) SYSThis word is used when compiling another word that is to be executed on a warm-reset (like the SYSTEM RESET key). This word should be the very first word in a colon definition. The remainder of the new word definition will be executed each warm-restart
PAD ( --> addr ) FIGReturns address of scratch area (usually 68 bytes beyond HERE)
SP@ ( n --> ) FIGReturns address of top stack item

String Functions#

" text" ( -$> $ ) SYSPushes a string constant on top of the str ng stack
"" ( -$> $ ) SYSPush the empty string on top of the string stack
! ( vaddr --> ) ( $ -$> ) SYSStore the string at the top of the string stack into the string variable
+ ( $1 $2 -$> $1+$2 ) SYSConcatenate the top two strings on the string stack
+! ( vaddr --> ) ( $ -$> ) SYSConcatenate the top string of the string stack onto the end of the string variable
. ( $ -$> ) SYSType the string at the top of the string stack
< ( --> f ) ( $1 $2 -$> ) SYSCompare the top two strings on the string stack and return true if $1 < $2
= ( --> f ) ( $1 $2 -$> ) SYSCompare the top two strings on the string stack and return true if $1 = $2
@ ( vaddr --> ) ( -$> $ ) SYSFetch the string from the string variable, and place it on top of the string stack
COMPARE ( --> n ) ( $1 $2 -$> ) SYSCompare the top two strings on top of the string stack. Return 1, 0, -1
DROP ( $2 $1 -$> $2 ) SYSDrop top value from string stack
DUP ( $1 -$> $1 $1 ) SYSDuplicate the string at the top of the string stack
EXTRACT ( vaddr offset char --> offset true ) ( -$> wd ) --> false ) ( -$> ) SYS Extracts substrings from a string, starting at the offset within the string looking for the next occurrence of the character. If there is another of the character (or a substring between the offset and the end of the string variable), then true is returned along with the new offset. Otherwise false is returned. This function is useful to extract words from a sentence.
FETCH ( addr len --> ) ( -$> $ ) SYSFetch the string starting at the address, with its length as indicated, and place it on the top of the string stack
FILL ( n c --> ) ( -$> $ ) SYSCreate a string at the top of the string stack which has n characters (c)
LEN ( --> n ) SYSReturn length of the string on top of the string stack
P! ( --> ) SYSReset string stack pointer
P@ ( --> n ) SYSReturns value of string stack pointer
P2 ( --> n ) SYSReturn the address of the 2nd string on the string stack (the string below the top string)
STORE ( addr max --> actlen ) ( $ -$> ) SYSStore the string on top of the string stack at the indicated address. The string will be stored up to the indicated maximum, the actual length of the string stored will be returned on top of the stack
SWAP ( $1 $2 -$> $2 $1 ) SYSSwap the top two strings on the string stack
VARFILL ( vaddr c --> ) SYSFill the string variable with the character (c)
VARIABLE xx ( len --> ) SYSCreates a string variable with maximum length as indicated
VARLEN ( vaddr --> len ) SYSReturn the length of the string currently in the string variable
VARMAX ( vaddr --> max ) SYSReturn the maximum string length of the string variable
*$* ( --> ) SYSVariable containing the size of the string stack (512 byte default)

ATARI Input/Output(CIO) Functions#

#0 ( --> ) SYSIocb offset for #0
#3 ( --> ) SYSIocb offset for #3
#4 ( --> ) SYSIocb offset for #4
#5 ( --> ) SYSIocb offset for #5
#6 ( --> ) SYSIocb offset for #6
FILE ( --> addr ) ( $ -$> $+EOL ) SYSMakes the string at the top of the string stack into a file name (terminated by an EOL) and returns the starting address on top of the stack. This file name can now be used by CIO functions (OPEN, XIO)
(STAT) ( --> n ) extStatus of previous CIO call
?DISKERROR ( --> ) extAborts and prints an error message if the previous CIO operation had an error
CLOSE ( iocb --> ) extCloses file using iocb
GET ( iocb --> b ) extGets a single byte using the given iocb. Check (STAT) for End-Of-File
GETBUF ( iocb addr len --> actlen ) extPerforms a get buffer operation using the indicated iocb. The buffer starts at the indicated address and has the indicated length. The transfer will end when the buffer is full, or the end-of-file is reached. The actual length of the data transferred will be returned on the stack
GETREC ( iocb addr len --> actlen ) extSame as GETBUF, except the transfer will be terminated at an EOL (End Of Line). This is a get record operation
JSRCIO ( iocb cmd --> ) extPerforms a call to the Operating System CIO routine. Iocb is the I/O Control block offset and cmd is the CIO command code. The status is stored in (STAT)
NOTE ( iocb --> sector disp ) extNotes position in disk file
OPEN ( iocb aux1 aux2 nameaddr --> ) extOpens file using iocb, 2 auxilliary bytes (see CIO), and name (terminated by EOL)
POINT ( iocb sector disp --> ) extPoints to position in disk file
PUT ( iocb b --> ) extOutput a single byte using the iocb
PUTBUF ( iocb addr len --> ) extOutputs the buffer using the iocb. The buffer starts at the indicated address and has the given length.
PUTREC ( iocb addr len --> ) extOutputs the record starting at the address, with given length. The record will be terminated by an EOL
STATUS ( iocb --> status ) extPerforms a status I/O operation using given iocb
XIO ( cmd iocb aux1 aux2 addr --> ) SYSSames as BASIC XIO function. Calls CIO

ATARI Forth File Functions#

LOAD ( filespec -$> ) SYSOpen the file as DR1, select DR1, and load the file (starting at screen 1)
SETDR0 ( filespec -$> ) SYSOpen the file as DR0
SETDR1 ( filespec -$> ) SYSOpen the file as DR1
LOAD-ED ( --> ) SYSLoad the screen editor from EDITOR.4TH
LOAD-DOS ( --> ) SYSLoad the DOS utilities from DOS.4TH
LOAD-TURN ( --> ) SYSLoad the turnkey software generator from TURNKEY.4TH
TURNKEY ( filespec -$> ) SYSSave the current loaded Forth words (including the entire Forth program, but not including the DOS from DOS.SYS)

General ATARI Input/Output Functions#

COLOR ( color --> ) SYSSelects color to use
CVTSTK ( n1 --> n2 ) SYSConverts joystick value to a more usable number (0=nothing, 1=up, 2=up-right, 3=right, 4=down-right, 5=down, 6=down-left, 7=left, 8=up-left)
DR. ( x y --> ) SYSDraws a line from the current position to the X-Y coord.
GR. ( mode --> ) SYSOpens screen for graphics I/O using iocb #6
LOC. ( x y --> value ) SYSSets the cursor to the X-Y coord. and determines the color of that point
PL. ( x y --> ) SYSSets the cursor to the X-Y coord. and plots the point
POS. ( x y --> ) SYSSets cursor to the X-Y coord.
SE. ( reg hue lum --> ) SYSSets a color register to the indicated hue and luminosity
SO. ( voice pitch dist vol --> ) SYSSets the voice to the desired pitch, distortion and volume
STICK ( port --> ) SYSReads the indicated joystick port (0,1,2,3)
STRIG ( port --> f ) SYSReads joystick trigger port, returns true if trigger not pushed

ATARI Disk Handler Functions#

COPY ( --> ) DISKMakes a bit copy of a disk from drive 1 to drive 2. It reports the status of each read and write on the screen. It will not abort if it should encounter read errors (say from a missing sector on the disk)
DMP ( sector --> ) DISK Reads a disk sector into a buffer at hex 8000. It reads the sector from drive 2. The sector is then dumped to the screen
GETSECTOR ( drive addr sector --> status ) DISK Performs a get of the sector on the indicated disk drive (1,2,3,4). The sector (128 bytes) will be read in starting at the address. The sector number (1 to 720) indicates the disk sector. The status of the read will be returned on the stack
PUTSECTOR ( drive addr sector --> status )DISK Writes a sector to disk. Similar to GETSECTOR

ATARI DOS Functions#

DELETE ( filespec -$> ) DOS Deletes the file(s). .Warning. there will be no confirmation like normal DOS
DIR ( filespec -$> ) DOS Lists a directory of the given file(s)
FORGET DOS ( --> ) DOS Used to forget DOS (after it has been loaded)
LOCK ( filespec -$> ) DOS Locks the file(s)
RENAME ( " Dn:file,file" -$> ) DOS Renames file(s)
SCRCOPY ( strt end --> ) ( filespec -$> ) DOS Creates a new file, copying screens from the current file (DR0/DR1) to the new file
UNLOCK ( filespec -$> ) DOS Unlocks the file(s)