% FastBasic %VERSION% - Fast BASIC interpreter for the Atari 8-bit computers Introduction ============ `FastBasic` is a fast interpreter for the BASIC language on the Atari 8-bit computers. One big difference from other BASIC interpreters in 1980s era 8-bit computers is the lack of line numbers, as well as an integrated full-screen editor. This is similar to newer programming environments, giving the programmer a higher degree of flexibility. Another big difference is that default variables and operations are done using integer numbers; this is one of the reasons that the programs run so fast relative to its peers from the 1980s. The other reason is that the program is parsed on run, generating optimized code for very fast execution. Currently, FastBasic supports: - Integer and floating point variables, including all standard arithmetic operators. - All graphic, sound, and color commands from Atari BASIC, plus some extensions from TurboBASIC XL. - All control flow structures from Atari BASIC and TurboBASIC XL. - Automatic string variables of up to 255 characters. - Arrays of "word", "byte", floating point and strings. - User defined procedures, with integer parameters. - Compilation to binary loadable files. - Available as a full version `FB.COM`, as a smaller integer-only `FBI.COM`, and as a command-line compiler `FBC.COM`. First Steps =========== To run FastBasic from the included disk image, simply type `FB` at the DOS prompt. This will load the IDE and present you with a little help text: --D:HELP.TXT-------------------0-- ' FastBasic %VERSION% - (c) 2024 dmsc ' ' Editor Help ' ----------- ' Ctrl-A : Move to beginning of line ' Ctrl-E : Move to end of line ' Ctrl-U / Ctrl-I : Page up / down ' Ctrl-Z : Undo (only current line) ' Ctrl-C : Set Mark to current line ' Ctrl-V : Paste from Mark to here ' Ctrl-Q : Exit to DOS ' Ctrl-S : Save file ' Ctrl-L : Load file ' Ctrl-N : New file ' Ctrl-R : Parse and run program ' Ctrl-W : Compile to binary file ' Ctrl-G : Go to line number ' '- Press CONTROL-N to begin - You are now in the integrated editor. On the first line of the screen the name of the currently edited file is shown, and at the right the line on which the cursor is located. Please note that lines that show an arrow pointing to the top-left are empty lines beyond the last line of the current file. In this example, the cursor is in the first column of the first line of the file being edited. As the help text says, just press the `CONTROL` key and the letter `N` (at the same time) to begin editing a new file. If the text was changed, the editor asks if you want to save the current file to disk; to skip saving simply type `CONTROL-C`; to cancel the New File command type `ESC`. Now you are ready to start writing your own BASIC program. Try the following example, pressing `RETURN` after each line to advance to the next: INPUT "WHAT IS YOUR NAME?";NAME$ ? ? "HELLO", NAME$ The parser will let you know if you made any mistakes. To make corrections move back using the cursor keys, this is `CONTROL` and `-`, `=`, `+` or `*`, then press `BACKSPACE` key to delete the character before the cursor or press `DELETE` (`CONTROL` and `BACKSPACE`) to delete the character below the cursor. To join two lines, go to the end of the first line and press `DELETE`. After typing the last line, you can run the program by pressing `CONTROL` and `R`. If there are no errors with your program, it will be run now: the computer screen will show `WHAT IS YOUR NAME?`, type anything and press `RETURN`, the computer will reply with a greeting and the program will end. After this, the IDE waits for any key press before returning to the editor, so you have a chance to see your program's output. If you press the `BREAK` key when the program is running, it will terminate, wait for a key press and return to the IDE. If you made a mistake typing in the program code, instead of the program running, the cursor will move to the line and column of the error so you can correct it and retry. Remember to save often by pressing the `CONTROL` and `S` keys and entering a filename. Type the name and press `ENTER` to save. As with any prompt, you can press `ESC` to cancel the save operation. Use the `BACKSPACE` over the proposed file name if you want to change it. Compiling The Program To Disk ============================= Once you are satisfied with your program, you can compile to a disk file, producing a program that can be run directly from DOS. Press the `CONTROL` and `W` key and type a filename for your compiled program. It is common practice to name your compiled programs with an extension of ".COM" or ".XEX." With ".COM" extension files you don't need to type the extension in some versions of DOS on the Atari. The ".XEX" name is common in modern times to distinguish Atari executables from MSDOS/Windows programs (which are usually ".EXE" or sometimes ".COM") Compiled programs include the full FastBasic runtime, so you can distribute them alone without the IDE. You can also compile a program directly from DOS by using the included command line compiler `FBC.COM`. The compiler prompts for the input file name, loads the BASIC source, compiles it, and prompts for a executable output filename to write the compiled program to. Advanced Editor Usage ===================== The editor includes a few commands, most of those are already explainded above. - `CONTROL-A` and `CONTROL-E` Moves the cursor ro the beginning or the end of the line respectively. - `CONTROL-U` and `CONTROL-I` Moves the cursor 19 lines up or down respectively. - `CONTROL-G` Moves the cursor to a specific line. - `CONTROL-Z` Reverts all editing of the current line. Note that changing the line clears the undo buffer, so you can't undo more than one line. - `CONTROL-C` Sets the current line as the source for a copy operation. - `CONTROL-V` Copy one line from the source marked with the `CONTROL-C` to the current cursor position. After the copy, the source line is advanced, so by pressing `CONTROL-V` multiple times you can copy multiple consecutive lines. - `CONTROL-L` and `CONTROL-S` Loads a file, or Saves the file being edited, respectively. - `CONTROL-Q` Returns to DOS, abandoning the changes in the current file. - `CONTROL-R` Parses the current program and runs it. - `CONTROL-W` Compiles the current program and saves it to a binary file. Making the Editor Faster ======================== The FastBasic IDE uses the Atari screen handler for writing text, so it is compatible with all 80 column and other expansions available. As the original screen handler in the Atari OS is slow, there is a screen accelerator included on the FastBasic disk. To use the accelerator, just type `EFAST` in the DOS prompt, before loading the IDE, and enjoy editing programs faster. About The Syntax ================ The syntax of FastBasic language is similar to many BASIC dialects, with the following main rules: 1. A program line must be of 4 types: - a comment line, starting with a dot `.` or an apostrophe `'`, - a statement followed by its parameters, - a variable assignment, this is a name followed by `=` and a the expression for the new value. For string variables, there is also a concatenation operator, `=+`. - an empty line. 2. All statements and variable names can be lower or uppercase, the language is case insensitive. 3. Statements can be abbreviated to reduce typing; each statement has a different abbreviation. 4. Multiple statements can be put on the same line by placing a colon `:` between statements. 5. After any statement a comment can be included by starting it with an apostrophe `'`. 6. No line numbers are allowed. 7. Spaces after statements and between operators are optional and ignored. In the following chapters, whenever a value can take any numeric expression, it is written as "_value_", and whenever you can use a string it is written as "*text*". Expressions =========== Expressions are used to perform calculations in the language. There are numeric expressions (integer and floating point), boolean expressions, and string expressions. In FastBasic, standard numeric expressions are evaluated as integers from -32768 to 32767, this is called 16 bit signed integer values. Floating point expressions are used *only* if numbers have a decimal point. Floating point numbers are stored with standard Atari binary-coded decimal (BCD) representation, with a range from 1E-98 to 1E+98. Boolean expressions are "true" or "false", represented as the numbers 1 and 0, respectively. String expressions contain arbitrary text. In FastBasic strings can have up to 255 characters of length. (This is similar to Microsoft BASICs found on other 8-bit microcomputers, and in contrast to the 32K limit found in Atari BASIC and TurboBASIC XL.) Numeric Values -------------- Integer values can be written as decimal numbers (like `123`, `1000`, etc.), as hexadecimal numbers with a $ sign before (like `$1C0`, `$A00`, etc.) or by using the name of a variable. Floating point values are written with a decimal dot and an optional exponent (like `3.14159`, `-3.2`, or `1.0E+10`). Numeric Variables ----------------- Variable names must begin with a letter or the symbol `_`, and can contain any letter, number or the symbol `_`. Examples of valid integer variable names are `COUNTER`, `My_Var`, `num1`. Floating point variables have an `%` as last character in the name. Examples of valid floating point variable names are `MyNum%`, `x1%`. In FastBasic, variables can't be used in an expression before being assigned a value; the first assignment declares the new variable. Numeric Operators ----------------- There are various "operators" that perform calculations in expressions. The operators with higher precedence always executed first. The order of precedence for *integer* operators are: - `+` `-` : addition, subtraction, from left to right. - `*` `/` `MOD`: multiplication, division, modulus, from left to right. - `&` `!` `EXOR`: binary 'and', 'or', 'exclusive or', from left to right. - `+` `-` : positive / negative. For example, an expression like: `1 + 2 * 3 - 4 * -5` is evaluated in the following order: - First, the unary `-` before the `5`, giving the number `-5`. - The first multiplication, giving `2*3` = `6`. - The second multiplication, giving `4*-5` = `-20`. - The addition, giving `1+6` = `7`. - The subtraction, giving `7 - -20` = `27`. So, in this example the result is 27. If there is a need to alter the precedence, you can place expressions within parenthesis (e.g., "`(2+5)*10`", which results in `70`). Note that `MOD` and `EXOR` can be abbreviated `M.` and `E.` respectively. When using floating point expressions, the operators are: - `+` `-` : addition, subtraction, from left to right. - `*` `/` : multiplication, division, from left to right. - `^` : exponentiation, from left to right. - `+` `-` : positive / negative. Note that integer expressions are automatically converted to floating point if needed, as this allows mixing integers and floating point in some calculations, but you must take care to force floating point calculations to avoid integer overflows. Example: the expression - a% = 1000 * 1000 + 1.2 gives correct result as 1000 is converted to floating point before calculation, but: x=1000: a% = x * x + 1.2 gives incorrect results as the multiplication result is bigger than 32767. Note that after any floating point errors (division by 0 and overflow), `ERR()` returns 3. Boolean Operators ----------------- Boolean operators return a "true" or "false" value instead of a numeric value, useful as conditions in loops and `IF` statements. Note that any boolean value can also be used as a numeric value, in this case, "true" is converted to 1 and "false" converted to 0. The supported boolean operators, in order of precedence, are: - `OR` : Logical OR, true if one or both operands are true. - `AND` : Logical AND, true only if both operands are true. - `NOT` : Logical NOT, true only if operand is false. - `<=` `>=` `<>` `<` `>` `=` For integer or floating point comparisons, compare the two numbers and return true or false. Note that `<>` is _not equal_. You can only compare two values of the same type, so an expression like `x = 1.2` is invalid, but `1.2 = x` is valid as the second operand is converted to floating point before comparison. The words `OR`, `AND` and `NOT` can be abbreviated `O.`, `A.` and `N.` Arrays ------ Arrays hold many ordered values (called elements). The array elements can be accessed by an index. In FastBasic, arrays must be dimensioned before use (see `DIM` statement below). The index of the element is written between parentheses and goes from 0 to the number of elements. Note that FastBasic does not check for out of boundary accesses, so you must be careful with your code to not overrun the size of the arrays. You can use an array position (the variable name followed by the index) in any location where a standard numeric variable or value is expected. Arrays can be of four types: - `WORD` arrays (the default if no type is given) use two bytes of memory for each element, and works like normal numeric integer variables. - `BYTE` arrays use only one byte for each element, so the numeric range is reduced from 0 to 255. - Floating point arrays, works like any floating point variable, and use six bytes of memory for each element. - String arrays store a string in each element. String arrays use two bytes of memory for each element that is not yet assigned (containing empty strings), and 258 bytes for each element with a string assigned. String Values ------------- String values are written as a text surrounded by double quotes (`"`). If you need to include a double quote character in a string, you must write two double quotes together. Example: PRINT "Hello ""world""" Will print: Hello "world" You can also include any character with it's hexadecimal code using `$` just after the closing quote, with no spaces around. This is the only way to include an ENTER character inside a string constant, see this example: PRINT "Hello"$9B"world"$2E$2E Will print: Hello world.. The bracket operator `[` `]` allows creating a string from a portion of another, and accepts two forms: - [ _start_ ] This form selects all characters from _start_ up to the end of the string, counting from 1. So, `A$[1]` selects the entire string, while `A$[3]` selects from the third character to the end, effectively removing the two leftmost characters. - [ _start_ , _len_ ] This form selects at most _len_ characters from _start_, or up to the end of the string if there is not enough characters. Example: PRINT "Hello World"[7] A$ = STR$(3.1415)[3,3] ? A$ ? A$[2,1] Will print: World 141 4 Note that the bracket operator creates a new string and copies the characters from the original string to the new one. As the same buffer is always used for the new string, you can't compare two values without first assigning one of them to a new string variable. This will print "ERROR": A$="Don't Work" IF A$[2,2] = A$[3,3] THEN ? "ERROR" while this will print "GOOD" A$="Long string" B$=A$[2,2] IF B$ <> A$[3,3] THEN ? "GOOD" String Variables --------------- The naming convention for string variables is the same as for numeric variables, but must end with a `$` symbol. Examples of valid string variable names are `Text$`, `NAME1$`. String variables always use 256 bytes, the first byte storing the string length and the following bytes storing up to 255 ATASCII characters. There are two types of string assignments: - The standard `=` sign copies the string expression in the right to the variable in the left. - The `=+` sign copies the string expression at the right to the end of the current string, concatenating the text. Example: A$ = "Hello " A$ =+ "World" ? A$ Will print: Hello World Functions --------- Functions take parameters (normally between parentheses) and return a result. Functions can be abbreviated by using a shorter name ended in a dot, for example you can write `R.(10)` instead of `RAND(10)`. You can also omit parentheses on functions that take only one argument, for example, `RAND 10`. Note: This is not possible when the function accepts a variable number of arguments (as with `USR`), or with the `ADR` function. Some functions don't take parameters, and you must provide a set of parentheses, like `KEY()`. However, when abbreviated, you can omit the parenthesis, like `K.` for `KEY()`. Standard Functions ------------------ Following is a list of all the general purpose functions supported by FastBasic. Shown are the full syntax and the abbreviated syntax. - TIME / T. : Returns the current time in "jiffies." This is about 60 times per second in NTSC systems or 50 times per second in PAL systems. Use `TIMER` statement to reset to 0. Note: TIME is special, and does not need parentheses. - ABS(_num_) / A.(_num_) : Returns the absolute value of _num_ (e.g., `ABS(5)` and `ABS(-5)` both result in `5`). Can be used with integers and floating point. - SGN(_num_) / SG.(_num_) ; Returns the sign of _num_, this is 1 if positive, -1 if negative or 0 if _num_ is 0. Can be used with integers and floating point. - RAND(_num_) / R.(_num_) : Returns a random, non negative number, a maximum of 1 less than _num_. - FRE() / F. : Returns the free memory available in bytes. - ERR() / E. : Returns the last Input/Output error value, or 1 if no error was registered. - LEN(*string*) / L.(*string*) : Returns the length of the *string*. - VAL(*string*) / V.(*string*) : Converts *string* to a number. If no conversion is possible, `ERR()` is set to 18. Can be used with integers and floating point. - ASC(*string*) / AS.(*string*) : Returns the ATASCII code of the first character of the *string*. Atari Specific Functions ------------------------ The following functions allow interacting with the Atari hardware to read controller and keyboard input and to program with Player/Missile graphics. - PADDLE(_n_) / PA.(_n_) : Returns the value of the PADDLE controller _n_. - PMADR(_n_) / PM.(_n_) : Returns the address of the data for Player _n_ or the address of the Missiles with _n_ = -1. - PTRIG(_n_) / PT.(_n_) : Returns 0 if the PADDLE controller _n_ button is pressed, 1 otherwise. - STICK(_n_) / S.(_n_) : Returns the JOYSTICK controller _n_ position. `STICK(_n_)` values are: `10` `14` ` 6` `11` `15` ` 7` ` 9` `13` ` 5` - STRIG(_n_) / STR.(_n_) : Returns 0 if JOYSTICK controller _n_ button is pressed, 1 otherwise. - KEY() / K. : Returns 0 if no key was pressed, or a keycode. The returned value only goes to 0 after reading the key in the OS (via a `GET` or `POKE 764, 255` statement). _Hint: The value returned is actually the same as_ `(PEEK(764) EXOR 255)`. The following program will show the `KEY()` codes for pressed keys: PRINT "Press keys, exit with ESC" REPEAT REPEAT : UNTIL KEY() PRINT "Key code: "; KEY() GET K PRINT "ATASCI code: "; K UNTIL K=27 Floating Point Functions ------------------------ These functions use floating point values, and are only available in the floating point version. In case of errors (such as logarithm or square root of negative numbers and overflow in the results), the functions will return an invalid value, and the `ERR()` function returns 3. - ATN(_n_) / AT.(_n_) : Arc-Tangent of _n_. - COS(_n_) / CO.(_n_) : Cosine of _n_. - EXP(_n_) : Natural exponentiation. - EXP10(_n_) / EX.(_n_) : Returns ten raised to _n_. - INT(_num_) / I.(_num_) : Converts the floating point number _num_ to the nearest integer from -32768 to 32767. - LOG(_n_) : Natural logarithm of _n_. - LOG10(_n_) / LO.(_n_) : Decimal logarithm of _n_. - RND() / RN. : Returns a random positive number strictly less than 1. - SIN(_n_) / SI.(_n_) : Sine of _n_. - SQR(_n_) / SQ.(_n_) : Square root of _n_. String Functions ---------------- - STR$(_num_) : Returns a string with a printable value for _num_. Can be used with integers and floating point. Note that this function can't be used at both sides of a comparison, as the resulting string is overwritten each time it is called. - CHR$(_num_) : Converts _num_ to a one character string with the ATASCII value. Low level Functions ------------------- The following functions are called "low level" because they interact directly with the hardware. Use with care! - ADR(_arr_) / &_arr_ : Returns the address of the first element of _arr_ in memory. Following elements of the array occupy adjacent memory locations. Instead of `ADR(X)` you can simply type `&X`. - ADR(_str_) / &_str_ : Returns the address of the _string_ in memory. The first memory location contains the length of the string, and following locations contain the string characters. (This differs from Atari BASIC and TurboBASIC XL, where the address returned points to the first character of the string.) - ADR(_var_) / &_var_ : Returns the address of the _variable_ in memory. - DPEEK(_addr_) / D.(_addr_) : Returns the value of memory location _addr_ and _addr_+1 as a 16 bit integer. This is the same as doing PEEK(_addr_)+PEEK(_addr_+1)*256 - PEEK(_address_) / P.(_address_) : Returns the value of memory location at _address_. - USR(_address_[,_num1_ ...]): Low level function that calls the user supplied machine code subroutine at _address_. Parameters are pushed to the CPU stack, with the LOW part pushed first, so the first PLA returns the HIGH part of the last parameter, and so on. The value of the A and X registers is used as a return value of the function, with A the low part and X the high part. This is a sample usage code snippet: ' PLA / EOR $FF / TAX / PLA / EOR $FF / RTS DATA ml() byte = $68,$49,$FF,$AA,$68,$49,$FF,$60 FOR i=0 TO 1000 STEP 100 ? i, USR(ADR(ml),i) NEXT i - $(_addr_) : Returns the string at memory address _addr_. This is the inverse of `ADR()`, and can be used to create arbitrary strings in memory. For example, the following code prints "AB": DATA x() byte = 2, $41, $42 ? $( ADR(x) ) Also, you can store string addresses to reuse later, using less memory than copying the full string: x = ADR("Hello") ? $( x ) - %(_n_) : This returns the floating-point value stored at memory address _n_. List Of Statements ================== In the following descriptions, statement usage is presented and the abbreviation is given after a /. Console Print and Input Statements ---------------------------------- **Reads Key From Keyboard** **GET _var_ / GE.** Waits for a keypress and writes the key value to _var_, which can be a variable name or an array position (like "array(123)") **Input Variable Or String** **INPUT _var_ / I.** **INPUT "prompt"; _var_** **INPUT "prompt", _var_** **INPUT ; _var_** Reads from keyboard/screen and stores the value in _var_. A "?" sign is printed to the screen before input, or the "prompt" if given. Also, if there is a comma after the prompt, spaces are printed to align to a column multiple of 10 (similar to how a comma works in `PRINT`). In the case you don't want any prompt, you can use a semicolon alone. If the value can't be read because input errors, the error is stored in ERR variable. Valid errors are 128 if BREAK key is pressed and 136 if CONTROL-3 is pressed. In case of a numeric variable, if the value can't be converted to a number, the value 18 is stored in ERR(). See the _Device Input and Output Statements_ section for the `INPUT #` usage. **Moves The Screen Cursor** **POSITION _column_, _row_ / POS.** Moves the screen cursor position to the given _column_ and _row_, so the next PRINT statement outputs at that position. Rows and columns are numerated from 0. **Print Strings And Numbers** **PRINT _expr_, ... / ?** **PRINT _expr_ TAB(_expr_) ...** **PRINT RTAB(_expr_) ...** **PRINT COLOR(_expr_) ...** **PRINT _expr_ ; ...** Outputs strings and numbers to the screen or other output device. Each _expr_ can be a constant string, a string variable or any complex expression, with commas or semicolons between each expression. If the first expression is a device I/O channel (e.g., `PRINT #1,"HELLO"`) the output will be sent to that device. In `GRAPHICS` modes other than 0 (e.g., large text `GRAPHICS 2`, multicolor text `GRAPHICS 12`, or even bitmapped graphics modes), use `#6` to write to that part of the screen. After writing the last expression, the cursor advanced to a new line, except if the statement ends in a comma, semicolon or `TAB`, where the cursor stays in the last position. If there is a comma before any expression, spaces are printed to advance the printing column to the next multiple of 10, allowing easy printing of tabulated data. The `COLOR` function alters the color the text that follows, until the end of the statement, depending on the graphics mode. This is abbreviated `C.`. Use 0 or 128 in graphics 0, for normal or inverse video. Use 0, 32, 128 or 160 in graphics mode 1 and 2 for the four available text colors, see the two examples below: ' In GRAPHICS 0: ? "NORMAL"; COLOR(128) "INVERSE" ' In GRAPHICS 2: S = 1234 ? #6, "SCORE: "; COLOR(32) S The `TAB` function advances the position to a column multiple of the argument, so that `TAB(10)` is the same as using a comma to separate arguments. This is abbreviated `T.`. The `RTAB` function, abbreviated `RT.`, advances the position so that the next argument to print ends just before a column multiple of the argument, right aligning the printing of the data. This function must be immediately followed by a variable or a string to align. Note that `,`, `TAB` and `RTAB` always print at least one space, and that to separate `TAB` or `RTAB` and the previous and next arguments you can use a `;` or simply a space. See the _Device Input and Output Statements_ section for the `PRINT #` usage. This example shows the usage of `TAB` and `RTAB`, note that the columns will be left and right aligned respectively: FOR i=0 TO 10 n = i*(9-2*i)*134 ? TAB(8) "Val:" RTAB(20) n NEXT The output is: Val:0 0 Val:1 938 Val:2 1340 Val:3 1206 Val:4 536 Val:5 -670 Val:6 -2412 Val:7 -4690 Val:8 -7504 Val:9 -10854 Val:10 -14740 *Advanced:* To implement the spacing on `,`, `TAB` and `RTAB`, FastBasic uses the current column in the OS, so that `POSITION` and printing to a graphics screen will work ok, unlike Atari BASIC; but when printing to a file or other devices the number of spaces will not be correct. Avoid using the functions to print to any device except the screen. *Advanced:* The `COLOR` function does an *exclusive or* of the given value with the value of each character in the original string before printing. **Writes A Character To Screen** **PUT _num_ / PU.** Outputs one character to the screen, given by it's ATASCII code. **Clears The Screen** **CLS** Clears the text screen. This is the same as `PUT 125`. For clearing the graphics screen, you can use `CLS #6`. Control Statements ------------------ **Endless Loops** **DO** **LOOP / L.** Starts and ends an endless repetition. When reaching the LOOP statement the program begins again, executing from the DO statement. The only way to terminate the loop is via an EXIT statement. **Calls A Subroutine** **EXEC _name_ _num1_, ... / EXE. / @** Calls the subroutine _name_, with the optional parameters _num1_ and so on, separated by commas. Note that the subroutine must be defined with PROC with the same number of parameters, but can be defined before or after the call. Instead of `EXEC` you can simply use a `@` in front of the procedure name. (i.e., these are equivalent: `EXEC GAMEOVER` and `@GAMEOVER`.) **Exits From Loop Or PROC** **EXIT / EX.** Exits current loop or subroutine by jumping to the end. In case of loops, the program continues after the last statement of the loop. In case of PROC, the program returns to the calling EXEC. **Loop Over Values Of A Variable** **FOR _var_=_value_ TO _end_ [STEP _step_] / F. T. S.** **NEXT _var_ / N.** FOR loop allows performing a loop a specified number of times while keeping a counting variable. First assigns the _value_ to _var_, and starts iterations. _var_ can be any variable name or a word array position (like "array(2)"). In each iteration, the command first compares the value of _var_ with _end_, if the value is past the end it terminates the loop. At the end of the loop, _var_ is incremented by _step_ (or 1 if STEP is omitted) and the loops repeats. An EXIT statement also terminates the loop and skips to the end. Note that if _step_ is positive, the iteration ends when the value of _var_ is bigger than _end_, but if _step_ is negative, the iteration ends if value of _var_ is less than _end_. Also, _end_ and _step_ are evaluated only once at beginning of the loop; that value is stored and used for all loop iterations. If at the start of the loop _value_ is already past _end_, the loop is completely skipped. A slightly modified usage of the FOR/NEXT loop allows for excluding the variable name from NEXT; this is required if _var_ is an array. This is an example of NEXT without variable: ' sample of FOR/NEXT loop without ' NEXT variable name FOR i=0 to 1000 step 100 ? i NEXT **Conditional Execution** **IF _condition_ THEN _statement_ / I. T.** **IF _condition_** **ELIF _condition_ / ELI.** **ELSE / EL.** **ENDIF / E.** The first form (with THEN) executes one _statement_ if the condition is true. This differs from Atari BASIC, TurboBASIC XL, and others, which will execute all statements after THEN until the end of the line. For example: A=1 IF A=0 THEN ? "ZERO":? "THE END" Results in "THE END" being printed in FastBasic, whereas nothing would be printed in Atari BASIC. The second form executes all statements following the IF (up until an ELIF, ELSE, or ENDIF) only if condition is true. If the condition is false, optional statements following the ELSE (until an ENDIF) are executed. In case of an ELIF, the new condition is tested and acts like a nested IF until an ELSE or ENDIF. This is an example of a multiple IF/ELIF/ELSE/ENDIF statement: IF _condition-1_ ' Statements executed if ' _condition-1_ is true ELIF _condition-2_ ' Statements executed if ' _condition-1_ is false but ' _condition-2_ is true ELIF _condition-3_ ' Also, if _condition-1_ and ' _condition-2_ are false but ' _condition-3_ is true ELSE ' Executed if all of the above ' conditions are false ENDIF **Define A Subroutine.** **PROC _name_ _var1_ .../ PR.** **ENDPROC / ENDP.** PROC statement starts the definition of a subroutine that can be called via EXEC or `@`. You can pass a list of integer variables separated by spaces after the PROC name to specify a number of parameters, the variables will be set to the values passed by the EXEC call. Those variable names are always global, so the values set are seen outside the PROC. The number of parameters in the PROC definition and in all the EXEC calls must be the same. Note that if the PROC statement is encountered while executing surrounding code, the full subroutine is skipped, so PROC / ENDPROC can appear any place in the program. **Loop Until Condition Is True** **REPEAT / R.** **UNTIL _condition_ / U.** The REPEAT loop allows looping with a condition evaluated at the end of each iteration. Executes statements between REPEAT and UNTIL once, then evaluates the _condition_. If false, the loop is executed again, if true the loop ends. An EXIT statement also terminates the loop and skips to the end. **Loop while condition is true** **WHILE _condition_ / W.** **WEND / WE.** The `WHILE` loop allows looping with a condition evaluated at the beginning of each iteration. Firstly it evaluates the condition. If false, it skips the whole loop to the end. If true, it executes the statements between `WHILE` and `WEND` and returns to the top to test the condition again. An EXIT statement also terminates the loop and skips to the end. Graphic and Sound Statements ---------------------------- **Set Color Number** **COLOR _num_ / C.** Changes the color of `PLOT`, `DRAWTO` and the line color on `FILLTO` to _num_. **Draws A Line** **DRAWTO _x_, _y_ / DR.** Draws a line from the last position to the given _x_ and _y_ positions. **Sets Fill Color Number** **FCOLOR _num_ & FC.** Changes the filling color of `FILLTO` operation to _num_. **Fill From Line To The Right** **FILLTO _x_, _y_ / FI.** Draws a line from the last position to the given _x_ and _y_ position using `COLOR` number. For each plotted point it also paints all points to the right with the `FCOLOR` number, until a point with different color than the first is reached. **Sets Graphic Mode** **GRAPHICS _num_ / G.** Sets the graphics mode for graphics operations. Below is a basic chart of GRAPHICS modes, their full screen resolution and number of available colors.[^1] Text modes[^2][^3][^4]: |Mode | Resolution | # Of Colors | |------ | ---------- | ------------ | |GR. 0 | 40x24 | 2 | |GR. 1 | 20x24 | 5 | |GR. 2 | 20x12 | 5 | |GR. 12 | 40x24 | 5 | |GR. 13 | 40x12 | 5 | Bitmapped graphics modes:[^5] |Mode | Resolution | # Of Colors | |------ | ---------- | ------------- | |GR. 3 | 40x24 | 4 | |GR. 4 | 80x48 | 2 | |GR. 5 | 80x48 | 4 | |GR. 6 | 160x96 | 2 | |GR. 7 | 160x96 | 4 | |GR. 8 | 320x192 | 2 | |GR. 9 | 80x192 | 16 shades | |GR. 10 | 80x192 | 9 | |GR. 11 | 80x192 | 16 hues | |GR. 14 | 160x192 | 2 | |GR. 15 | 160x192 | 4 | [^1]: `GRAPHICS 0` and `GRAPHICS 8` offer two colors, where the "on" pixels may be a different shade (luminence) of the background color's hue, but cannot have its own hue. (Television color artifacting effects can be utilized to simulate two additional colors.) Use `SETCOLOR 2,H,L1` and `SETCOLOR 1,0,L2` (or `POKE 710,H*16+L1` & `POKE 709,L2`). [^2]: Mode 0 (and the text window found at the bottom of most other modes) can render 128 different characters (from a character set, aka font) in both normal video, and inverse video, based on whether the high bit of the character is set. See `PRINT COLOR()`. [^3]: Modes 1 and 2 are text modes that offer multiple colors, but only a single color (plus the background) may be used by any given character cell. The colors are chosen by the two high bits of the character. This means only half of a character set (font) -- 64 shapes -- may normally be used. See `PRINT COLOR()`. [^4]: Modes 12 and 13 are mutlicolor text modes, where every pair of two bits in a character's bitmap data are used to represent one of four colors. As with mode 0, 128 characters may be used. However, when the high bit is set (which produces an inverse-video effect in mode 0), the effect in these modes is to change which color palette register is used for the fourth color (pixels comprised of `11` bits); instead of `SETCOLOR 2` (aka `POKE 710`), the color from `SETCOLOR 3` (aka `POKE 711`) will be used. See `PRINT COLOR()`. [^5]: The so-called "GTIA modes" -- 9, 10, and 11 -- offer 16 shades of the given background color (use `SETCOLOR 4,H,0` or `POKE 712,H*16`), all nine color registers (`SECTOLOR N,H,L` or `POKE 704+N,H*16+L`), or 15 hues of a particular brightness (the background remains darkest; use `SETCOLOR 4,0,L`), respectively. For graphics modes which include a 4-line `GRAPHICS 0` style text window at the bottom (all but 0, 9, 10, and 11), add 16 to the mode number to disable the text window. (e.g., `GRAPHICS 2+16`) Add 32 to the mode number to prevent the graphics data from being cleared. (Note: Some graphics data may be replaced when changing modes.) *Advanced:* The Atari OS `S:` screen device dictate which `GRAPHICS` modes are available. However (as demonstrated by the text window), the Atari can mix graphics modes via use of Display Lists. The ANTIC graphic chip uses a different set of values to reflect the different graphics modes (and modes 9, 10 and 11 utilize a feature managed by the GTIA chip), as well as other features (blank scanlines, fine scrolling, Display List Interrupts, etc.) Consult _De Re Atari_ chapter 2, "ANTIC and the Display List" for more details. **Get color of pixel** **LOCATE _x_, _y_, _var_ / LOC.** Reads the color of pixel in the specified _x_ and _y_ coordinates and store into variable _var_. **Plots A Single Point** **PLOT _x_, _y_ / PL.** Plots a point in the specified _x_ and _y_ coordinates, with the current `COLOR` number. **Player/Missile Graphics Mode** **PMGRAPHICS _num_ / PMG.** Set up Atari Player / Missile graphics. A value of 0 disables all player and missiles; a value of 1 sets up single line resolution; a value of 2 sets up double line resolution. Single line mode uses 256 bytes per player, while double line uses 128 bytes per player. (Note that all four missiles share the same data.) For retrieving the memory address of the player or missile data use the `PMADR()` function. **Player/Missile Horizontal Move** **PMHPOS _num_,_pos_ / PM.** Set the horizontal position register for the player or missile _num_ to _pos_. Players 0 to 3 correspond to values 0 to 3 of _num_; missiles 0 to 3 correspond to the values 4 to 7, respectively. This is the same as writing: `POKE $D000 + num , pos` Note: Player/Missile graphics on the Atari are strips that are as tall as the screen, and therefore to move a shape vertically its data must be moved within their 128- or 256-byte buffer (using the `MOVE` statement, for example). **Sets Displayed Color** **SETCOLOR _num_, _hue_, _lum_ / SE.** Alters the color registers so that color number _num_ has the given _hue_ and _luminance_. To set Player/Missile colors use negative values of _num_, -4 for player 0, -3 for player 1, -2 for player 2, and -1 for player 3. Missiles share the same color as their player, unless you combine them into a "5th Player" by setting bit number 4 of the `GPRIOR` register, e.g.: `POKE 623,16`. (You must also move them horizontally in unison if you wish to use them as a true 5th Player.) It is possible to cause pixels of certain overlapping players to produce a third color (or black) by setting bit number 5 of the `GPRIOR` register, e.g. `POKE 623,32`. Consult the `GPRIOR` section of _Mapping the Atari_ for more details. **Adjust Voice Sound Parameters** **SOUND _voice_, _pitch_, _dist_, _vol_ / S.** **SOUND _voice_** **SOUND** Adjusts sound parameters for _voice_ (from 0 to 3) of the given _pitch_, _distortion_ and _volume_. If only the _voice_ parameter is present, that voice is cleared so no sound is produced by that voice. If no parameters are given, it clears all voices so that no sounds are produced. Note: TurboBASIC XL offers a `DSOUND` statement to pair sound channels for increased (16-bit) frequency range. This is not available in FastBasic. Device Input and Output Statements ---------------------------------- **Binary read from file** **BGET #_iochn_,_address_,_len_ / BG.** Reads _length_ bytes from the channel _iochn_ and writes the bytes to _address_. For example, to read to a byte array, use `ADR(array)` to specify the address. On any error, `ERR()` will hold an error code, on success `ERR()` reads 1. **Binary Read From File** **BPUT #_iochn_,_address_,_len_ / BP.** Similar to `BPUT`, but writes _length_ bytes from memory at _address_ to the channel _iochn_. On any error, `ERR()` will hold an error code, on success `ERR()` reads 1. **Close Channel** **CLOSE #_iochn_ / CL.** Closes the input output channel _iochn_, finalizing all read/write operations. On any error, `ERR()` will hold an error code, on success `ERR()` reads 1. Note that it is important to read the value of `ERR()` after close to ensure that written data is really on disk. **Reads bytes from file** **GET #_iochn_, _var_, ...** Reads one byte from channel _iochn_ and writes the value to _var_. _var_ can be a variable name or an array position (like `array(123)`) In case of any error, `ERR()` returns the error value. **Input Variable Or String From File** **INPUT #_iochn_, _var_ / IN.** Reads a line from channel _iochn_ and stores to _var_. If _var_ is a string variable, the full line is stored. If _var_ is a numeric variable, the line is converted to a number first. On any error, `ERR()` will hold an error code, on success `ERR()` reads 1. **Opens I/O Channel** **OPEN #_ioc_,_mode_,_ax_,*dev* / O.** Opens I/O channel _ioc_ with _mode_, _aux_, over device *dev*. To open a disk file for writing, _mode_ should be 8, _aux_ 0 and *dev* the file name as "D:name.ext". To open a disk file for reading, _mode_ should be 4, _aux_ 0 and *dev* the file name as "D:name.ext". See Atari BASIC manual for more documentation in the open modes, aux values, and device names. On any error, `ERR()` will hold an error code, on success `ERR()` reads 1. **Print Strings And Numbers To A File** **PRINT #_iochn_, ... / ?** Uses the same rules as the normal print, but all the output is to the channel _iochn_. Note that you must put a comma after the channel number, not a semicolon. On any error, ERR() will hold an error code, on success ERR() reads 1. Note that you can only read the error for the last element printed. **Outputs One Byte To The File** **PUT #_iochn_, _num_ / PU.** Outputs one byte _num_ to the channel _iochn_. On any error, ERR() will hold an error code, on success ERR() reads 1. **Generic I/O Operation** **XIO #_iochn_, _cmd_, _aux1_, _aux2_, *dev* / X.** Performs a general input/output operation on device *dev*, over channel _ioc_, with the command _cmd_ ,and auxiliary bytes _aux1_ and _aux2_. Note that the arguments of XIO statements are in different order than Atari BASIC, for consistency with other statements the _iochn_ is the first argument. Example: to delete the file "FILE.TXT" from disk, you can do: XIO #1, 33, 0, 0, "D:FILE.TXT" General Statements ------------------ **Line comments** **' / .** Any line starting with a dot or an apostrophe will be ignored. This is analogous to REM in Atari BASIC. **Clears variables and free memory** **CLR** Clears all integer and floating-point variables to 0, all strings to empty strings and frees all memory associated with arrays. After `CLR` you can't access arrays without allocating again with `DIM`. **Defines array with initial values** **DATA _arr()_ [type] = n1,n2, / DA.** This statement defines an array of fixed length with the values given. The array name should not be used before, and type can be `BYTE` (abbreviated `B.`) or `WORD` (abbreviated `W.`). If no type is given, a word data is assumed. If you end the `DATA` statement with a comma, the following line must be another `DATA` statement without the array name, and so on until the last line. Example: DATA big() byte = $12,$23,$45, DATA byte = $08,$09,$15 Note that the array can be modified afterwards like a normal array. *Advanced Usage* Byte DATA arrays can be used to include assembler routines (to call via `USR`, see the example above), display lists and any other type of binary data. To facilitate this, you can include constant strings and the address of other byte DATA array by name. All the bytes of the string, including the initial length byte are included into the DATA array. Example: DATA str() B. = "Hello", "World" X = ADR(str) ? $(X), $(X+6) DATA ad() B. = $AD,str,$A2,0,$60 ? USR(ADR(ad)), str(0) *Loading data from a file* The cross-compiler also supports loading data from a file directly into the program, using the `BYTEFILE` (abbreviated `BYTEF.`) and `WORDFILE` (abbreviated `WORDF.` or simply `F.`) types and a file name enclosed in double quotes. Example: DATA img() bytefile "img.raw" DATA pos() wordfile "pos.bin" The compiler will search the file in the same folder than the current basic source. *Storing data into ROM* In addition to the above, the cross compiler allows to specify that the data should be stored in ROM, instead of the default in RAM. This means that the data can't be modified in targets that use ROM (cartridges), but will lower RAM usage. To specify this, simply add the `ROM` word after the type: DATA img() ROM 1234,5678 DATA pos() BYTE ROM 1,2,3,4 **Decrements variable by 1** **DEC _var_ / DE.** Decrements the variable by 1; this is equivalent to "_var_ = _var_ - 1", but faster. _var_ can be any integer variable or integer array element. **Allocate an Array / Define Var** **DIM _arr_(_size_) [type], .../ DI.** **DIM _var_, _var$_, _var%_ ...** The `DIM` statement allows defining arrays of specified length, and declaring variables explicitly, without assigning a value. The type must be `BYTE` (abbreviated `B.`) to define a byte array, with numbers from 0 to 255, or `WORD` (can be left out) to define an array with integers from -32768 to 32767. If the name _arr_ ends with a `$` or a '%' symbol, this defines a string array or floating point array respectively, in this case you can't specify a type. The size of the array is the number of elements plus one, the elements are numerated from 0, so that an array dimensioned to 10 holds 11 values, from 0 to 10. The array is cleared after the `DIM`, so all elements are 0 or an empty string. In the second form, the variables given in the list are defined with the correct type, without giving a default value. The variables can be defined multiple times without an error if the types are always the same. You can `DIM` more than one array or variable by separating the names with commas. Example: DIM A(10), X, T$ ? A(5), X **Ends Program** **END : Ends program.** Terminates current program. END is only valid at end of input. **Increments Variable By 1** **INC _var_** Increments the variable by 1, this is equivalent to "_var_ = _var_ + 1", but faster. _var_ can be any integer variable or integer array element. **Pauses Execution** **PAUSE _num_ / PA.** **PAUSE** Stops the current execution for the specified amount of time. _num_ is the time to pause in "jiffies", this is the number of TV scans in the system; 60 per second in NTSC or 50 per second in PAL. Omitting _num_ is the same as giving a value of 0, and pauses until the vertical retrace. This is useful for synchronization to the TV refresh and for fluid animation. **Resets internal timer** **TIMER/ T.** Resets value returned by `TIME` function to 0. Floating Point Statements ------------------------- Those statements are only available in the floating point version. **Sets "degrees" mode** **DEG** Makes all trigonometric functions operate in degrees, so that 360 is the full circle. **Sets "radians" mode** **RAD** Makes all trigonometric functions operate in radians, so that 2pi is the full circle. This mode is the default on startup. Low Level Statements -------------------- These are statements that directly modify memory. Use with care! **Writes a 16bit number to memory** **DPOKE _address_, _value_ / D.** Writes the _value_ to the memory location at _address_ and _address+1_, using standard CPU order (low byte first). **Copies Bytes In Memory** **MOVE _from_, _to_, _length_ / M.** **-MOVE _from_, _to_, _length_ / -.** Copies _length_ bytes in memory at address _from_ to address _to_. The `MOVE` version copies from the lower address to the upper address; the `-MOVE` version copies from upper address to lower address. The difference between the two MOVE statements is in case the memory ranges overlap; if _from_ is lower in memory than _to_, you need to use `-MOVE`, else you need to use `MOVE`, otherwise the result will not be a copy. `MOVE a, b, c` is equivalent to: FOR I=0 to c-1 POKE b+I, PEEK(a+I) NEXT I but `-MOVE a, b, c` is instead: FOR I=c-1 to 0 STEP -1 POKE b+I, PEEK(a+I) NEXT I **Sets Memory To A Value** **MSET _address_, _length_, _value_ / MS.** Writes _length_ bytes in memory at given _address_ with _value_. This is useful to clear graphics or P/M data, or simply to set an string to a repeated value. `MSET a, b, c` is equivalent to: FOR I=0 to b-1 POKE a+I, c NEXT I **Writes A Byte To Memory** **POKE _address_, _value_ / P.** Writes the _value_ (modulo 256) to the memory location at _address_. Display List Interrupts ----------------------- *Note: This is an advanced topic.* Display list interrupts (normally called `DLI`) are a way to modify display registers at certain vertical positions on the screen. You can use them to: - Display more colors in the image, by changing color registers - registers from $D012 to $D01A. - Split one Player/Missile graphics to different horizontal positions - registers from $D000 to D007. - Change scrolling position, screen width, P/M width, etc. FastBasic allows you to specify one or more DLI routines, activate one or deactivate all DLI by using the `DLI` statement: **Define a new DLI** **DLI SET _name_ = _op1_, _op2_, ... / DLIS.** Setups a new DLI with the given name and performing the _op_ operations. Each operation is of the form: _data_ `INTO` _address_ or _data_ `WSYNC` `INTO` _address_. _data_ is one constant byte or the name of a `DATA BYTE` array, and _address_ is a memory location to modify. If _data_ is a DATA array, the first element (at index 0) will be used at the first line with DLI active in the screen, the second element at the second active line, etc. The `WSYNC` word advances one line in the display area (this is done by writing to the `WSYNC` ANTIC register), so the value is set in the next screen line. You can put the `WSYNC` word multiple times to advance more than one line. This allows one DLI to modify multiple lines at the screen. Multiple `INTO` words can be used to write more than one register with the same value. `INTO` can be abbreviated to `I.` and `WSYNC` to `W.`. You can specify any number of operations, but as each one takes some time you could see display artifacts if you use too many. Note that by defining a DLI you are simply giving it a name, you need to activate the DLI afterwards. You can split a DLI definition over multiple lines, just like DATA by ending a line with a comma and starting the next line with `DLI =` **Enable a DLI** **DLI _name_ / DL.** This statement enables the DLI with the given name, the DLI must be defined before in the program. This setups the OS DLI pointer to the named DLI and activates the interrupt bit in the display processor (the ANTIC chip), but does not activates on which lines the DLI must be called. To define on which lines the DLI is active you must modify the _Display List_, see the example at the end of the section. You can also pass the name of a DATA BYTE array with a custom machine language routine to the `DLI` statement, the routine must begin with a _PHA_ and end with _PLA_ and _RTI_. **Disable a DLI** **DLI / DL.** This statement simply disables the DLI, returning the display to the original **DLI Examples** This is the most basic example of a DLI that simply changes the background color at the middle of the screen: ' Define the DLI: set background ' color to $24 = dark red. DLI SET d1 = $24 INTO $D01A ' Setups screen GRAPHICS 0 ' Alter the Display List, adds ' a DLI at line 11 on the screen POKE DPEEK(560) + 16, 130 ' Activate DLI DLI d1 ' Wait for any keyu ? "Press a Key" : GET K ' Disable the DLI DLI The next example shows how you can use a DLI to change multiple values in the screen: ' An array with color values DATA Colors() BYTE = $24,$46,$68 ' Define the DLI: set background ' color from the Color() array ' and text back color with value ' $8A in the same line and then ' the black in to the next line. DLI SET d2 = Colors INTO $D01A, DLI = $8A INTO $D018, DLI = $00 WSYNC INTO $D018 ' Setups screen GRAPHICS 0 ' Adds DLI at three lines: POKE DPEEK(560) + 13, 130 POKE DPEEK(560) + 16, 130 POKE DPEEK(560) + 19, 130 ' Activate DLI DLI d2 ' Wait for any keyu ? "Press a Key" : GET K ' Disable the DLI DLI The final example shows how you can move multiple P/M using one DLI ' Player shapes, positions and colors DATA p1() BYTE = $E7,$81,$81,$E7 DATA p2() BYTE = $18,$3C,$3C,$18 DATA pos() BYTE = $40,$60,$80,$A0 DATA c1() BYTE = $28,$88,$C8,$08 DATA c2() BYTE = $2E,$80,$CE,$06 ' Our DLI writes the position and ' colors to Player 1 and Player 2 DLI SET d3 = pos INTO $D000 INTO $D001, DLI = c1 INTO $D012, c2 INTO $D013 GRAPHICS 0 : PMGRAPHICS 2 ' Setup our 4 DLI and Players FOR I = 8 TO 20 STEP 4 POKE DPEEK(560) + I, 130 MOVE ADR(p1), PMADR(0)+I*4+5,4 MOVE ADR(p2), PMADR(1)+I*4+5,4 NEXT ' Activate DLI DLI d3 ? "Press a Key" REPEAT PAUSE pos(0) = pos(0) + 2 pos(1) = pos(1) + 1 pos(2) = pos(2) - 1 pos(3) = pos(3) - 2 UNTIL KEY() DLI **Some useful registers** This is a table of some useful registers to change during a DLI: |Address| Register | | ----- | ------------------------- | | $D000 | Player 0 horizontal pos. | | $D001 | Player 1 horizontal pos. | | $D002 | Player 2 horizontal pos. | | $D003 | Player 3 horizontal pos. | | $D004 | Missile 0 horizontal pos. | | $D005 | Missile 1 horizontal pos. | | $D006 | Missile 2 horizontal pos. | | $D007 | Missile 3 horizontal pos. | | $D012 | Color of player/missile 0 | | $D013 | Color of player/missile 1 | | $D014 | Color of player/missile 2 | | $D015 | Color of player/missile 3 | | $D016 | Color register 0 | | $D017 | Color register 1 | | $D018 | Color register 2 | | $D019 | Color register 3 | | $D01A | Color of background | Atari SIO Statements -------------------- The Atari Serial Input Output interface is the low-level interface between the Atari 8-bit computers and the serial peripherals, like disk-drives and modems. **Send any command over SIO** **SIO _ddevic_, _dunit_, _dcomnd_, _dstats_, _dbuf_, _dtimlo_, _dbyt_, _daux1_, _daux2_** This function can be used to send any SIO command to any SIO device. For example, this command is used to read or write one sector in a floppy disk, or send special commands to a FujiNet network device. | Parameter | Description | | --------- | ---------------------- | | DDEVIC | Device # (e.g. $71) | | DUNIT | Unit # | | DCOMND | Command # ($00-$FF) | | DSTATS | Read($40) / Write($80) | | DBUF | Target buffer address | | DTIMLO | Timeout value | | DBYT | # of bytes in payload | | DAUX1 | First Aux parameter | | DAUX2 | Second Aux parameter | The meanings of each of these is highly dependent on the target device. **Get last SIO error function** **SERR() / SE.** This function returns the value in `DSTATS`, which contains the error of the last SIO operation from the device. In the context of the FujiNet device, can be used, along with `DVSTAT+4` to determine any error from a network operation. FujiNet Statements ------------------ These are statements that talk to the FujiNet network adapter, and can be used to open network connections, using any protocol supported. Each of these statements require a _unit_ number, of which 8 are available, numbered 1-8. The general flow of use is: * `NOPEN` a connection * In a loop * Check for any traffic with `NSTATUS` * `NGET` if needed * Send any traffic with `NPUT` * When done, `NCLOSE`. **Open a Network Connection** **NOPEN _unit_, _mode_, _trans_, _url_ / NO.** Uses `N:` _unit_ to open a connection to _url_ using the desired _mode_ and _trans_ settings. Example URLs might be: `N:HTTPS://www.gnu.org/licenses/gpl-3.0.txt` Common _modes_: - 4: READ, mapped e.g. to GET in HTTP - 6: DIRECTORY, e.g. PROPFIND in HTTP - 8: WRITE, mapped e.g. to PUT in HTTP - 12: READ/WRITE, e.g. for TCP - 13: Mapped to POST in HTTP Common _trans_: - 0: No translation of characters. - 1: Change CR to ATASCII EOL. - 2: Change LF to ATASCII EOL. - 3: Change CR and LF to EOL. **Close a Network Connection** **NCLOSE _unit_ / NC.** Closes a network connection _unit_ previously opened by `NOPEN`. **Get Network Connection Status** **NSTATUS _unit_ / NS.** Queries the status of specified network _unit_. The result is stored in `DVSTAT` starting at `$02EA`, and has the format: | Address | Description | | ------- | ----------------------- | | $02EA | # of bytes waiting (LO) | | $02EB | # of bytes waiting (HI) | | $02EC | Connected? (0 or 1) | | $02ED | Most recent error # | You can easily get the # of bytes waiting by doing the following: NSTATUS 1 BW = DPEEK($02EA) **Read Bytes from Network to _addr_** **NGET _unit_, _addr_, _len_ / NG.** **Write bytes to Network from _addr_** **NPUT _unit_, _addr_, _len_ / NG.** These two functions are complements of each other, reading and writing _len_ bytes to and from _addr_ as needed. When reading, _len_ must be less than, or equal to the number of bytes waiting to be received, or an SIO error will result. Therefore, it is a good idea to figure out how many bytes are waiting using the `NSTATUS` command. Conversely, when writing, _len_ must be less than, or equal to the number of bytes in the source buffer. For example all of the available SIO commands for FujiNet Network at this link: [SIO Commands for FujiNet Devices](https://github.com/FujiNetWIFI/fujinet-platformio/wiki/SIO-Commands-for-Device-IDs-%2471-to-%2478)