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tt1542 edited this page Jun 8, 2026 · 17 revisions

BASCOMP 2.1 Supported Language Features

Notes:

  • Numeric values are 16-bit integer-style values.
  • Strings are counted runtime strings with a maximum payload length of 255 bytes.
  • File channels are 1 to 9.
  • Array indexes are 1-based.

Supported Statements

  • REM and apostrophe comments:
REM This is a comment
' This is also a comment
  • LET and implicit assignment without LET:
LET A = 10
A = A + 1
A$ = "HELLO"
  • INPUT ["prompt"], var
  • INPUT ["prompt"], var$
  • ! var as shorthand for INPUT var
INPUT "NAME", N$
INPUT "VALUE", A
! A
  • LINE INPUT #channel, var$
LINE INPUT #1, A$
  • PRINT
  • ? as shorthand for PRINT
  • PRINT #channel, ...
PRINT "HELLO"
? A
PRINT #2, "VALUE="; A
  • IF ... THEN ... ELSE ...
  • multi-line IF ... THEN, ELSEIF ... THEN, ELSE, END IF
  • GOTO
  • GOSUB + RETURN
  • ON expression GOTO ... — available since BASCOMP 2.1
  • ON expression GOSUB ... — available since BASCOMP 2.1 
ON A GOTO START, MIDDLE, FINISH
ON A GOSUB SUB1, SUB2, SUB3
  • FOR ... TO ... [STEP ...] / NEXT
  • END FOR
  • EXIT FOR — available since BASCOMP 2.1
  • WHILE ... / WEND
  • DIM for integer arrays
  • DIM name$ AS STRING * length — available since BASCOMP 2.1
  • DIM name$(count) AS STRING * maxLength — available since BASCOMP 2.1
  • OPEN ... FOR INPUT AS #channel
  • OPEN ... FOR OUTPUT AS #channel
  • CLOSE #channel
  • KILL
  • GET #channel, [position,] variable
  • PUT #channel, [position,] variable
  • CHDIR path$ — available since BASCOMP 2.1
  • MKDIR path$ — available since BASCOMP 2.1
  • RMDIR path$ — available since BASCOMP 2.1
  • FILES [filespec$] — available since BASCOMP 2.1
  • CLS
  • LOCATE row, column
  • COLOR foreground, background
  • SCREEN mode — available since BASCOMP 2.1
  • PSET x, y, color — available since BASCOMP 2.1
  • LINE (x1,y1)-(x2,y2), color [,B|BF] — available since BASCOMP 2.1
  • CIRCLE (x,y), radius [,color] — available since BASCOMP 2.1
  • BEEP — available since BASCOMP 2.1
  • DEF SEG
  • DEF SEG = expression
  • POKE offset, value
  • POKE segment, offset, value — available since BASCOMP 2.1
  • OUT port, value — available since BASCOMP 2.1
  • CALLINT interruptNumber, registerArray — available since BASCOMP 2.1
  • SELECT CASE, CASE, CASE ELSE, END SELECT
  • RANDOMIZE
  • RANDOMIZE TIMER / numeric-expression
  • RANDOMIZE TIMER() — available since BASCOMP 2.1
  • DATA — available since BASCOMP 2.1
  • READ — available since BASCOMP 2.1
  • RESTORE — available since BASCOMP 2.1
  • DATAB — available since BASCOMP 2.1
  • CALLDATA lineNumber — available since BASCOMP 2.1
  • XSET handle, index, string-expression
  • XFREE handle
  • END / STOP / . as shorthand

Supported Control Structures

IF / ELSE

BASCOMP supports single-line and multi-line IF forms in both traditional numbered BASIC mode and QB-style unnumbered mode.

Single-line form:

IF A > 10 THEN PRINT "HIGH" ELSE PRINT "LOW"

Multi-line form:

IF A > 10 THEN
  PRINT "HIGH"
ELSEIF A = 10 THEN
  PRINT "TEN"
ELSE
  PRINT "LOW"
END IF

Boolean IF expressions support AND, OR, and NOT in supported comparison contexts.

IF A > 0 AND B > 0 THEN PRINT "BOTH POSITIVE"
IF NOT A = 0 THEN PRINT "A IS NOT ZERO"

SELECT CASE

SELECT CASE supports numeric selection logic.

SELECT CASE A
  CASE 1
    PRINT "ONE"
  CASE 2
    PRINT "TWO"
  CASE ELSE
    PRINT "OTHER"
END SELECT

Current CASE handling is based on individual numeric case values and CASE ELSE.

FOR / NEXT / END FOR / EXIT FOR

Counted loops are supported, including nested loops and optional STEP values.

FOR I = 1 TO 10 STEP 2
  PRINT I
NEXT I

END FOR is recognized as an explicit loop terminator form.

EXIT FOR leaves the innermost active FOR loop. EXIT FOR is available since BASCOMP 2.1.

FOR I = 1 TO 10
  IF I = 5 THEN EXIT FOR
  PRINT I
END FOR

WHILE / WEND

A = 0

WHILE A < 10
  A = A + 1
WEND

ON GOTO / ON GOSUB

ON expression GOTO and ON expression GOSUB are available since BASCOMP 2.1. They use a 1-based target index.

A = 2
ON A GOTO ONE, TWO, THREE

ONE:
PRINT "ONE"
END

TWO:
PRINT "TWO"
END

THREE:
PRINT "THREE"
END
A = 1
ON A GOSUB SUB1, SUB2
END

SUB1:
PRINT "SUB1"
RETURN

SUB2:
PRINT "SUB2"
RETURN

Subroutines

Subroutines are supported through GOSUB and RETURN.

GOSUB HELLO
END

HELLO:
PRINT "HELLO"
RETURN

Supported Data Types

Numeric Variables

Numeric variables store signed 16-bit integer-style values.

A = 123
B = -10
C = A + B

String Variables

String identifiers end with $ and use counted string representation in the runtime.

A$ = "HELLO"
B$ = A$ + " WORLD"

Fixed-length string storage is available since BASCOMP 2.1:

DIM NAME$ AS STRING * 40
NAME$ = "BASCOMP"

Indexed Numeric Arrays

DIM creates indexed numeric arrays using syntax such as A(I). Array indexes are 1-based in the runtime.

DIM A(10)

A(1) = 5
A(2) = A(1) + 10

PRINT A(2)

Small arrays are stored internally. Larger numeric arrays are backed by external DOS memory through the runtime array support.

External String Arrays

External string arrays are available through XALLOC and through the DIM syntax introduced in BASCOMP 2.1.

Be careful: The maximum size of any individual array is 65535 Bytes (one segment). In the case of strings, this means you need to calculate: (stringlen+1)*stringnums <= 65535.

DIM-style external string arrays — available since BASCOMP 2.1

DIM NAMES$(10) AS STRING * 40

NAMES$(1) = "ALICE"
NAMES$(2) = "BOB"

PRINT NAMES$(1)

Handle-style external string arrays

H = XALLOC(10, 40)

XSET H, 1, "ALICE"
XSET H, 2, "BOB"

PRINT XGET$(H, 1)

XFREE H

XALLOC(count) uses the default maximum string length. XALLOC(count, maxLength) specifies the per-entry maximum payload length.

Supported Expressions

Numeric Expressions

Numeric expressions support:

  • decimal constants
  • hexadecimal constants with &H...
  • numeric variables
  • numeric array elements such as A(I)
  • parentheses
  • unary +
  • unary -
  • unary NOT
  • "+"
  • "-"
  • "*"
  • "/"
  • "\"
  • MOD
  • XOR
  • AND
  • OR
  • exponentiation with ^
  • numeric function calls

Examples:

A = 10 + 20 * 3
B = (A - 5) \ 2
C = A MOD 7
D = &HFF
E = NOT 0
F = 2 ^ 8

String Expressions

String expressions support:

  • string variables
  • string literals
  • string concatenation with +
  • string function calls
  • indexed external string array access
  • DATE$
  • TIME$
  • INKEY$
  • INPUT$

Examples:

A$ = "HELLO"
B$ = A$ + " WORLD"

C$ = LEFT$(B$, 5)
D$ = STR$(123)
E$ = DATE$
F$ = TIME$

Nested string expressions and concatenations are supported through the internal string-expression parser and temporary string buffers.

Supported Comparisons

The following comparison operators are supported in IF expressions:

  • "="
  • "<>"
  • "<"
  • ">"
  • "<="
  • ">="

Comparisons work for both numeric values and supported string expressions, depending on context.

IF A = 10 THEN PRINT "TEN"
IF A$ = "OK" THEN PRINT "MATCH"
IF LEFT$(A$, 1) = "Y" THEN PRINT "YES"

Supported Functions

Numeric and Conversion Functions

LEN(string)

Returns the length of a string.

A$ = "HELLO"
PRINT LEN(A$)

VAL(string)

Converts a string to a numeric value.

A$ = "123"
A = VAL(A$)

ASC(string)

Returns the character code of the first character.

A = ASC("A")
PRINT A

EOF(channel)

Returns the end-of-file state for a file channel.

OPEN "TEST.TXT" FOR INPUT AS #1

WHILE EOF(1) = 0
  LINE INPUT #1, A$
  PRINT A$
WEND

CLOSE #1

EXIST(string)

Tests whether a file exists.

IF EXIST("TEST.TXT") THEN PRINT "FILE EXISTS"

INSTR(string, pattern)

Searches for a substring and returns its position.

P = INSTR("ABCDEF", "CD")
PRINT P

INSTR(start, string, pattern)

Searches for a substring starting at a specific position.

P = INSTR(3, "ABABAB", "AB")
PRINT P

ABS(number)

Returns the absolute value.

PRINT ABS(-10)

SGN(number)

Returns -1, 0, or 1 depending on the sign of the value.

PRINT SGN(-20)
PRINT SGN(0)
PRINT SGN(20)

RND(number)

Returns a pseudo-random number in the supported runtime range.

RANDOMIZE TIMER
A = RND(100)
PRINT A

INT(number)

Returns the integer value. Since BASCOMP numeric values are already integer-style values, this is mainly useful for compatibility.

A = INT(123)

SQR(number)

Returns the integer square root.

PRINT SQR(100)

MIN(a, b)

Returns the smaller value.

PRINT MIN(10, 20)

MAX(a, b)

Returns the larger value.

PRINT MAX(10, 20)

TIMER()

Returns the number of seconds since midnight modulo 65536.

T = TIMER()
PRINT T

EXEC(program$, args$)

Starts a DOS child program and returns 0 on success or a DOS error code.

R = EXEC("CHILD", "")
IF R <> 0 THEN PRINT "EXEC ERROR "; R

Example with arguments:

R = EXEC("TOOL", "INPUT.TXT OUTPUT.TXT")
PRINT R

CPUID()

Detects the CPU class and returns the runtime CPU identifier.

Typical return values include:

  • 86 for 8086/8088 class
  • 120 for NEC V20/V30 class
  • 186 for 80186/80188 class
  • 286
  • 386
  • 486
  • 586
  • 686
  • 1500 for CPUID family F
  • 999 for CPUID-present but otherwise unmapped family
C = CPUID()
PRINT "CPU="; C

PEEK(offset)

Reads a byte from the active DEF SEG segment.

DEF SEG = &HB800
A = PEEK(0)
DEF SEG

PEEK(segment, offset)

Reads a byte from an explicit segment and offset. This form is available since BASCOMP 2.1.

A = PEEK(&HB800, 0)
PRINT A

INP(port)

Reads a byte from an I/O port. INP() is available since BASCOMP 2.1.

A = INP(&H60)
PRINT A

XALLOC(count)

Allocates an external string array with default maximum string length and returns a handle.

H = XALLOC(10)

XALLOC(count, maxLength)

Allocates an external string array with a specific maximum string length.

H = XALLOC(10, 40)
XSET H, 1, "HELLO"
PRINT XGET$(H, 1)
XFREE H

String-Producing Functions

CHR$(number)

Builds a one-character string from a character code.

A$ = CHR$(65)
PRINT A$

LEFT$(string, count)

Returns the left part of a string.

PRINT LEFT$("HELLO", 2)

MID$(string, start, count)

Returns a substring.

PRINT MID$("HELLO", 2, 3)

RIGHT$(string, count)

Returns the right part of a string.

PRINT RIGHT$("HELLO", 2)

LTRIM$(string)

Removes leading spaces.

PRINT LTRIM$("   HELLO")

RTRIM$(string)

Removes trailing spaces.

PRINT RTRIM$("HELLO   ")

TRIM$(string)

Removes leading and trailing spaces.

PRINT TRIM$("   HELLO   ")

UCASE$(string)

Converts ASCII lowercase letters a to z to uppercase.

PRINT UCASE$("Hello")

STR$(number)

Converts a numeric value to a string.

A$ = STR$(123)
PRINT A$

XGET$(handle, index)

Reads a string from an external string array.

H = XALLOC(5, 20)
XSET H, 1, "ONE"
PRINT XGET$(H, 1)
XFREE H

DATE$

Returns the DOS date in mm-dd-yyyy format.

PRINT DATE$

TIME$

Returns the DOS time in hh:mm:ss format.

PRINT TIME$

INKEY$

Returns a non-blocking keyboard input string.

K$ = INKEY$
IF LEN(K$) <> 0 THEN PRINT "KEY PRESSED"

Special keys may return a two-character string where the first byte is zero and the second byte is the scan code, depending on BIOS behavior.

INPUT$

Reads a string from standard input.

A$ = INPUT$
PRINT A$

DATA, READ, RESTORE, DATAB, and CALLDATA

DATA, READ, RESTORE, DATAB, and CALLDATA are available since BASCOMP 2.1.

DATA

Defines numeric word data.

DATA 10,20,30

READ A
READ B
READ C

PRINT A; B; C

READ

Reads the next numeric word from DATA.

DATA 100,200

READ A
READ B

RESTORE

Resets the runtime data pointer to the first DATA record.

DATA 1,2,3

READ A
READ B

RESTORE

READ C
PRINT C

DATAB

Defines raw byte data in the generated assembly.

100 DATAB 65,66,67

CALLDATA lineNumber

Calls the byte block generated by DATAB at the given BASIC source line number.

This is an advanced low-level feature. The byte block is treated as machine code and must return correctly, typically with RET, decimal opcode 195, if it is called as a subroutine.

Minimal safe example:

100 DATAB 195
110 CALLDATA 100
120 PRINT "RETURNED"

File I/O

Text file I/O is supported through:

  • OPEN
  • CLOSE
  • PRINT #
  • LINE INPUT #
OPEN "OUT.TXT" FOR OUTPUT AS #1
PRINT #1, "HELLO"
CLOSE #1
OPEN "OUT.TXT" FOR INPUT AS #1
LINE INPUT #1, A$
PRINT A$
CLOSE #1

Binary file I/O is supported through:

  • GET
  • PUT
OPEN "DATA.BIN" FOR OUTPUT AS #1
A = 65
PUT #1, 1, A
CLOSE #1
OPEN "DATA.BIN" FOR INPUT AS #1
GET #1, 1, A
PRINT A
CLOSE #1

File channels 1 to 9 are supported.

OPEN supports:

  • FOR INPUT
  • FOR OUTPUT

KILL deletes a file:

KILL "OLD.TXT"

EXIST() checks whether a file is present:

IF EXIST("OLD.TXT") THEN KILL "OLD.TXT"

The runtime retains buffered byte output for PUT; buffered binary output is flushed when required by handle changes, seek operations, close operations, and mixed text/binary output paths.

Directory and File Listing Support

Directory and file listing statements are available since BASCOMP 2.1.

CHDIR

Changes the current directory.

CHDIR "C:\TEMP"

MKDIR

Creates a directory.

MKDIR "TESTDIR"

RMDIR

Removes a directory.

RMDIR "TESTDIR"

FILES

Lists matching files.

FILES
FILES "*.BAS"

Directory entries are printed in brackets by the runtime.

Screen Output and Text Mode Control

Standard text output is supported through PRINT.

Additional screen control is provided by:

  • CLS
  • LOCATE
  • COLOR
CLS
COLOR 14, 1
LOCATE 10, 20
PRINT "HELLO"

COLOR foreground, background sets the active text attribute used by BIOS-style console output when screen output support is active.

Graphics Support

Graphics statements are available since BASCOMP 2.1.

SCREEN mode

SCREEN selects a BIOS video mode through the runtime.

Known mappings:

  • SCREEN 0 maps to BIOS text mode 03h
  • SCREEN 1 maps to BIOS mode 04h
  • SCREEN 2 maps to BIOS mode 06h
  • Other values are passed as BIOS mode numbers in AL; for example, SCREEN 13 selects BIOS mode 13h on systems that support it.

Examples:

SCREEN 0
PRINT "TEXT MODE"
SCREEN 13
PSET 160, 100, 12

PSET x, y, color

Plots one pixel using BIOS graphics output.

SCREEN 13
PSET 160, 100, 15

LINE (x1,y1)-(x2,y2), color

Draws a line.

SCREEN 13
LINE (10,10)-(200,100), 15

LINE (x1,y1)-(x2,y2), color, B

Draws a rectangle outline.

SCREEN 13
LINE (20,20)-(120,80), 14, B

LINE (x1,y1)-(x2,y2), color, BF

Draws a filled rectangle.

SCREEN 13
LINE (30,30)-(100,70), 4, BF

CIRCLE (x,y), radius [,color]

Draws an outline circle.

SCREEN 13
CIRCLE (160,100), 50, 15

If the color is omitted, the compiler/runtime path uses the default color handling implemented by the graphics parser.

Sound

BEEP

BEEP is available since BASCOMP 2.1. It outputs the bell character.

BEEP

Memory Access

BASCOMP 2.1 supports a compact BASIC-style memory access subset.

DEF SEG = expression

Sets the active segment used by PEEK(offset) and POKE offset,value.

DEF SEG = &HB800
A = PEEK(0)
DEF SEG

DEF SEG

Resets the active segment to the program segment.

DEF SEG

PEEK(offset)

Reads a byte from the active DEF SEG segment.

DEF SEG = &HB800
A = PEEK(0)

PEEK(segment, offset)

Reads a byte from an explicit segment and offset. This form is available since BASCOMP 2.1.

A = PEEK(&HB800, 0)

POKE offset, value

Writes a byte to the active DEF SEG segment and offset.

DEF SEG = &HB800
POKE 0, 65
DEF SEG

POKE segment, offset, value

Writes a byte to an explicit segment and offset. This form is available since BASCOMP 2.1.

POKE &HB800, 0, 65

Values written by POKE must fit into a byte, 0..255; otherwise the runtime raises a byte value error.

Port I/O

Port I/O is available since BASCOMP 2.1.

INP(port)

Reads one byte from an I/O port.

A = INP(&H60)
PRINT A

OUT port, value

Writes one byte to an I/O port.

OUT &H61, 0

The output value must fit into a byte, 0..255.

Interrupt Calls

CALLINT interruptNumber, registerArray

CALLINT is available since BASCOMP 2.1. It calls a real-mode interrupt using a numeric register array.

The array layout is:

  • regs(1) = AX
  • regs(2) = BX
  • regs(3) = CX
  • regs(4) = DX
  • regs(5) = SI
  • regs(6) = DI
  • regs(7) = FLAGS output only

Segment registers are not user-settable in this minimal runtime interface.

Example: call BIOS keyboard interrupt 16h, function 00h, to wait for and read a key.

DIM R(7)

R(1) = &H0000
R(2) = 0
R(3) = 0
R(4) = 0
R(5) = 0
R(6) = 0

CALLINT &H16, R

PRINT "AX="; R(1)
PRINT "FLAGS="; R(7)

Example: BIOS keyboard status, interrupt 16h, function 01h.

DIM R(7)

R(1) = &H0100

CALLINT &H16, R

IF R(7) AND &H40 THEN
  PRINT "NO KEY AVAILABLE"
ELSE
  PRINT "KEY AVAILABLE"
END IF

&H40 checks the zero flag bit in the returned FLAGS word.

Date, Time, Keyboard, EXEC, and CPU Support

BASCOMP 2.1 includes runtime support for:

  • DATE$ using DOS date services
  • TIME$ using DOS time services
  • TIMER() using DOS time services
  • INKEY$ using BIOS keyboard calls
  • EXEC() for launching DOS child programs
  • CPUID() for CPU-class detection

Examples:

PRINT DATE$
PRINT TIME$
PRINT TIMER()
K$ = INKEY$
IF LEN(K$) <> 0 THEN PRINT "KEY"
R = EXEC("CHILD", "")
IF R <> 0 THEN PRINT "EXEC ERROR "; R
PRINT CPUID()

Compatibility Notes and Limits

  • BASCOMP supports both numbered BASIC source mode and QB-style unnumbered source mode.
  • Numeric values are 16-bit integer-style values.
  • File channels are 1..9.
  • Array indexes are 1-based.
  • FOR/WHILE nesting depth is limited.
  • Block IF nesting depth is limited.
  • String expression and context nesting depth is limited by the compiler's internal context stacks.

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