Category : OS/2 Files
Archive   : P2C4OS2.ZIP
Filename : BASIC.DOC

Chipmunk BASIC 1.0
David Gillespie


--------------------------------------------------------------




COMMANDS


LIST line(s)

List the specified program lines. For example,

LIST 10, 100-200

lists line 10, and lines 100 through 200, inclusive.


RUN [line]

Begin execution of the program at the first line, or at the
specified line. All variables are cleared.


RUN file[,line]

Load and run a program. For example,

RUN "FOO", 30

loads a program from the file FOO.TEXT and begins execution at
line 30.


NEW

Erase the program in memory.


LOAD file

Load a program into memory. The program previously in memory is
erased. The file name should be in quotes; a .TEXT extension is
automatically added. Files contain ASCII listings of the programs.
All lines in the file must begin with a line number, but line
numbers do not need to be in increasing order.


MERGE file

Load a program into memory. The previous program remains in
memory; if a line exists in both programs, the newly loaded
line is kept.


SAVE file

Save the program in memory to a file.


BYE

Return to the operating system.


DEL line(s)

Delete the specified program lines. Line numbers may be
separated by commas and dashes as in LIST. If used inside
a program, DEL will terminate execution only if it deletes
the line on which it appears.


RENUM [start[,inc]]

Renumber program lines. By default, the new sequence is 10,20,30,...
The first argument is a new initial line number; the second argument
is the increment between line numbers.




STATEMENTS

REM comment

A remark; ignored. Comments may contain any characters except
that REM can not be immediately followed by an alphanumeric
character.


[LET] var = expr

Assign a value to a variable. Variable names contain up to 20
significant characters, consisting of upper- and lower-case
letters, digits, underscores, and dollar signs. Variable names
are case-sensitive. Variables hold real numbers normally, or
strings of up to 255 characters if their names end with $.

Examples:

LET X=20
X$="FOO"
X$=X$+"BAR"


DIM var(dimensions), ...

Allocate memory for arrays. Arrays may have up to 4 dimensions,
ranging from 0 to the value specified in the DIM statement.
The same name must not be used for both a simple variable and
an array.

If an array is used before it is dimensioned, each dimension
is set to 10.

Example:

INPUT "How many elements? "; x
DIM array(x,1)
FOR i=1 TO x : INPUT array(i,0), array(i,1) : NEXT


PRINT items

Print the items on the screen. Items may be either numeric
or string expressions, and may be separated by commas, semicolons,
or nothing.

Numbers are normally terminated by spaces. To avoid this space,
convert the number to a string with STR$.

The line is terminated by a CR/LF, unless the item list ends
with a comma or semicolon.

The word PRINT may be abbreviated as a question mark.

Examples:

PRINT "1+2=", 1+2
PRINT X$ "=" Z$;
? x; y+z


INPUT [prompt;] vars

If a prompt string is given, it is printed. Otherwise, a
question mark is printed. The computer then waits for values
for each variable to be entered. If several variables are
listed, their names must be separated by commas.

If the variables are numeric, their values may be entered
on separate lines, or combined with commas. Any numeric expression
is a valid response.

If the variables are strings, each string is typed on a separate
line. The characters typed are copied verbatim into the string.

String and numeric variables may be not mixed in a single
INPUT statement.

Examples:

INPUT X$
INPUT "Type 3 numbers: "; X, Y, Z


GOTO line

Begin executing statements at the specified line. The line
number may be any numeric expression.

The word GO TO may be used instead of GOTO if preferable.


IF condition THEN line/statements ELSE line/statements

If the condition is true (i.e., the numeric expression has a
non-zero value), the statements following the word THEN are
executed. Otherwise, the statements following ELSE are
executed. If there is no ELSE clause, execution proceeds
to the next line in the program.

A line number may be used after either THEN or ELSE, for an
implied GOTO statement.


END

Terminate the program. An END statement is not required.


STOP

Terminate the program with an identifying "Break" message.


FOR var = first TO last [STEP inc]
{statements}
NEXT [var]

Execute {statements} repeatedly while the variable counts from
"first" to "last," incrementing by 1, or by the STEP value if
given. If the STEP value is negative, the variable counts
downward.

If "first" is greater than "last" (or less than if STEP is
negative), execution proceeds directly to the NEXT statement,
without executing the body of the loop at all.

The variable name is optional on the NEXT statement.


WHILE [condition]
{statements}
WEND [condition]

Execute {statements} repeatedly until the WHILE condition (if
given) becomes false, or until the WEND condition becomes true.
This structure can emulate Pascal's WHILE-DO and REPEAT-UNTIL,
or even both at once. If no conditions are given, the loop will
never terminate unless the Evil GOTO is used.


GOSUB line
RETURN

Execute the statements beginning at the specified line, then
when RETURN is reached, return to the statement following the
GOSUB.


READ vars
DATA values
RESTORE line

Read numeric or string values from the DATA statements. Reading
begins at the first DATA statement in the program and proceeds
to the last. Reading past the end the last DATA statement
generates an error.

The DATA values must be either numeric or string expressions,
according to the type of variable being read. Reading the wrong
kind of expression produces a Syntax Error.

The RESTORE statement causes the next READ to re-use the first
DATA statement in the program, or the first DATA statement on
or after a particular line.


GOTOXY across, down

Move the cursor to the specified screen position, between
0,0 and 79,23.


ON expr GOTO line, line, ...
ON expr GOSUB line, line, ...

If the expression's value, rounded to an integer, is N, go to
the Nth line number in the list. If N is less than one or is
too large, execution continues at the next statement after
the ON-GOTO or ON-GOSUB.


POKE addr, data

Store a byte at the specified address.




NUMERIC EXPRESSIONS

x AND y

Logical AND of two integers.


x OR y

Logical OR of two integers.


x XOR y

Logical XOR of two integers.


NOT x

Logical complement of an integer.


x+y, x-y, x*y, x/y, x^y, -x

Typical floating-point arithmetic operations.


x=y, xy, x<=y, x>=y, x<>y

Comparisons; result is 1 if true, 0 if false.


x MOD y

Modulo of two integers.


SQR x

Square of X. Note that parentheses are not required if a function's
argument is a single entitity; for example, SQR SIN X needs no
parentheses, but SQR(1+X) does.


SQRT x

Square root of X.


SIN x, COS x, TAN x, ARCTAN x

Typical trig functions, in radians.


LOG x, EXP x

Natural logarithm, and e the power X.


ABS x

Absolute value of X.


SGN x

Sign of X: 1 if X is positive, 0 if zero, -1 if negative.


VAL x$

Value of the expression contained in the string X$. For example,
VAL "1+2" yields 3. X$ may be a single string literal, variable,
or function, or a string expression in parentheses.


ASC x$

ASCII code of the first character in X$, or 0 if X$ is null.


LEN x$

Number of characters in X$.


Precedence: Parentheses
Functions (incl. NOT and unary minus)
^
*, /, MOD
+, -
=, <, >, <=, >=, <>
AND
OR, XOR



STRING EXPRESSIONS

"string" or 'string'

String literal. Single quotes are converted to double quotes
internally.


x$+y$

Concatenation. Result must be 255 characters or less.


x$=y$, x$y$, x$<=y$, x$>=y$, x$<>y$

String comparisons; result is 1 if true, 0 if false.


STR$(x)

The number X expressed as a string of digits. No leading or
trailing spaces are included; scientific notation is used
if the absolute values is greater than 1E12 or less than 1E-2.


CHR$(x)

The character whose ASCII code is X.


MID$(x$, y)
MID$(x$, y, z)

(Parentheses required.) The substring consisting of the first
Z characters starting at position Y of string X$. Position 1
is the first character of the string. If Z is omitted, 255
is used, i.e., the entire right part of the string.



CONVENTIONS

Multiple statements may be written on a line, separated by colons:

10 INPUT X : PRINT X : STOP


There is actually no difference between commands and statements;
both can be used in or out of programs at will. Certain commands,
such as NEW, will, of course, halt program execution.


Line numbers may be any integer from 1 to MAXINT.


To delete a line use DEL, or type its line number alone:

10


Press CLR I/O to halt program execution. [This is not supported
by p2c's translation!] To leave BASIC, use the BYE command.


Keywords must be written in all upper- or all lower-case; they are
always converted to upper-case internally. Spaces are ignored in
the input except between quotes. Square brackets are converted to
parentheses. Missing closing quotes at the end of the line are
added, as in the command:

SAVE "PROGRAM