ABC Language Reference
Identifiers are alphanumeric strings starting with a nonnumeric character and ending :
- With nothing for identifiers
- With '$' for string-identifiers
- With '#' for boolean-identifiers
The interpreter uses a lexical binding, i.e. free variables in functions are bound to the
functions' compilation environment.
DIM
DIM identifier
( numeric-expression ) = numeric-expression
DIM string-identifier
( numeric-expression ) = string-expression
DIM boolean-identifier
( numeric-expression ) = boolean-expression
Declares an array of the given size. The array type is determined by the expression type.
FOR ... TO ... STEP ... NEXT
FOR identifier =
numeric-expression TO
numeric-expression [STEP
numeric-expression] instructions
NEXT [identifier]
A standard for loop, using an index and optionally a step, which can be negative. If
no identifier is found after the NEXT statement, it refers
to the previous FOR loop.
GOTO
GOTO identifier
Jumps to the given LABEL.
IF ... THEN ... ELSE
IF boolean-expression
THEN instruction [ELSE
instruction]
Evaluates the boolean-expression and executes the instruction
following the THEN keyword if the result is TRUE.
Otherwise, it executes the instruction
following the ELSE keyword if any, or jumps to the next instruction.
LABEL
LABEL identifier
Declares a LABEL, which can be accessed with a
GOTO statement.
LET
LET identifier
= numeric-expression
LET string-identifier
= string-expression
LET boolean-identifier
= boolean-expression
LET identifier
( numeric-expression )
= numeric-expression
LET string-identifier
( numeric-expression )
= string-expression
LET boolean-identifier
( numeric-expression )
= boolean-expression
Stores the rightmost expression's value into the given variable or array cell.
SUB ... ENDSUB
SUB identifier
( arguments ) instructions
ENDSUB
SUB string-identifier
( arguments ) instructions
ENDSUB
SUB boolean-identifier
( arguments ) instructions
ENDSUB
Declares a subroutine. The return type is determined by the identifier type.
INPUT
INPUT string, identifier
INPUT string, string-identifier
INPUT string, boolean-identifier
Prompts the user for either a number, string or boolean, displaying a string.
The result is then stored into the right identifier.
PRINT
PRINT print-arguments
PRINT print-arguments;
Prints the concatenation of the print-arguments, where print-arguments is
a list of numeric-expressions, string-expressions, or
boolean-expressions separated with commas. The string-expressions and
boolean-expressions are converted to strings before they are displayed. If the PRINT instruction
line ends with a semicolon, then no new line is appended at the end of the printed string.
GRAPHICS
GRAPHICS numeric-expression,
numeric-expression
Initializes a graphic window of the given width (first parameter) and height (second parameter).
RESIZE
GRAPHICS numeric-expression,
numeric-expression
Resizes the graphic window to the given width (first parameter) and height (second parameter).
MOVE
MOVE numeric-expression,
numeric-expression
Moves the current coordinates to the given x (first parameter) and y (second parameter).
PLOT
PLOT
Draws a point at the current coordinates in the graphic window.
LINETO
LINETO numeric-expression,
numeric-expression
Draws a line from the current coordinates to the given (first parameter, second parameter) coordinates,
and sets the current coordinates to (first parameter, second parameter).
COLOR
COLOR numeric-expression,
numeric-expression, numeric-expression
COLOR string-expression
Sets the current drawing color, using three values between 0 and 255 which represent respectively
the values of RED, GREEN, BLUE, or using a string representing the color, which can be:
- "BLACK"
- "WHITE
- "RED"
- "GREEN"
- "BLUE
- "YELLOW"
- "GRAY"
RECTANGLE
RECTANGLE numeric-expression,
numeric-expression
Draws an empty rectangle with the given width (first parameter) and height (second parameter) at the
current coordinates.
FILLEDRECTANGLE
FILLEDRECTANGLE numeric-expression,
numeric-expression
Draws a filled rectangle with the given width (first parameter) and height (second parameter) at the
current coordinates.
ELLIPSE
ELLIPSE numeric-expression,
numeric-expression
Draws an empty ellipse with the given width (first parameter) and height (second parameter) at the
current coordinates.
FILLEDELLIPSE
FILLEDELLIPSE numeric-expression,
numeric-expression
Draws a filled ellipse with the given width (first parameter) and height (second parameter) at the
current coordinates.
RND
RND ( numeric-expression )
Returns a random decimal number between 0 and the given value (first parameter).
INT
INT ( numeric-expression )
INT ( string-expression )
Returns the integer value of the given expression.
EXP
EXP ( numeric-expression )
Returns the exponential of the given expression.
LOG
LOG ( numeric-expression )
Returns the logarithm of the given expression.
SIN
SIN ( numeric-expression )
Returns the sine of the given expression.
COS
COS ( numeric-expression )
Returns the cosine of the given expression.
ASIN
ASIN ( numeric-expression )
Returns the arc sine of the given expression.
ACOS
ACOS ( numeric-expression )
Returns the arc cosine of the given expression.
ABS
ABS ( numeric-expression )
Returns the absolute value of the given expression.
SQR
SQR ( numeric-expression )
Returns the squared value of the given expression.
MOD
MOD ( numeric-expression,
numeric-expression )
Returns the first expression modulo the second expression.
LEN
LEN ( string-expression )
Returns the length of the given string.
ASC
ASC ( string-expression )
Returns the ASCII value of the first character from the given string.
LEFT$
LEFT$ ( string-expression,
numeric-expression )
Returns a string containing the leftmost characters of the given string. The wanted length is the second parameter.
RIGHT$
LEFT$ ( string-expression,
numeric-expression )
Returns a string containing the rightmost characters of the given string. The wanted length is the second parameter.
STR$
STR$ ( numeric-expression )
STR$ ( numeric-expression,
numeric-expression )
Returns the string representation of the given number. If a second parameter is given and the return value
would be shorter than this value, the string is padded with spaces to be as long as this value.
MID$
MID$ ( string-expression,
numeric-expression, numeric-expression )
STR$ ( string-expression,
numeric-expression )
Returns a substring of the first parameter starting at the position given by the second parameter,
with a length of the optional parameter. If no third parameter is given, the substring ends at the end
of the initial string.
WAIT
WAIT ( string-expression )
Waits for the given amout of time (in seconds).
