Veecom uBASIC

A Simple Interactive BASIC Interpreter for Veecom.

Table of Contents

• Introduction
  
• Variables
  
• Mathematical Operators
  
• Logical Operators
  
• Control Flow
  
• PEEK-POKE
  
• Additional Commands
  
• Examples
  
• Configuring uBASIC
  
• Compiling and Building uBASIC
  

Introduction

Veecom uBASIC is a derivative of the uBASIC interpreter originally authored by Adam Dunkels. This version of uBASIC has been improved to be made fully interactive, with the incorporation of additional commands and performance optimizations.

The interpreter provides flexibility in input methods, allowing users to either write commands directly or use line numbers.

Direct Command Input:

PRINT "HELLO, WORLD!"

Line-Numbered Programming:

10 PRINT "HELLO, WORLD!"
20 END

Direct commands are executed right away, whereas Line-Numbered commands require the execution of the RUN command afterward.

Variables

There is only support for integer variables and the variables can only have single character names (A-Z).

Valid Assignment

10 LET A = 10
20 LET B = 2 * A
30 LET C = B - A

Invalid Assignment

10 LET CE = 9
20 LET A = 2.4

Mathematical Operators

Addition ( + ):

LET N = 10 + 6

Subtraction ( - ):

LET N = 10 - 6

Multiplication ( * ):

LET N = 10 * 6

Division ( / ):

LET N = 10 / 6

Modulus ( % ):

LET N = 10 % 6

Logical Operators

Logical And ( & ):

LET N = 10 & 6

Logical Or ( | ):

LET N = 10 | 6

Less Than ( < ):

IF A < B THEN ...

Greater Than ( > ):

IF A > B THEN ...

Equal ( = ):

IF A = B THEN ... 

Control Flow

IF-THEN Statement

IF A < B THEN PRINT "A IS LESS"

FOR-NEXT Statement

10 FOR I = 1 TO 3
20 PRINT I * I
30 NEXT I
40 END

1
4
9

GOTO Statement

10 PRINT "HELLO, WORLD!"
20 GOTO 10

HELLO, WORLD!
HELLO, WORLD!
HELLO, WORLD!
HELLO, WORLD!
HELLO, WORLD!
...

GOSUB-RETURN

10 GOSUB 100
20 PRINT "RETURNED FROM SUBROUTINE"
30 END
100 PRINT "SUBROUTINE"
110 RETURN

SUBROUTINE
RETURNED FROM SUBROUTINE

PEEK-POKE

PEEK

A is assigned to the value held at address 65535

PEEK 65535, A

Variables can be used to hold addresses

10 LET A = 65532
20 PEEK A, B

POKE

The memory address is assigned to the value held by A

10 LET A = 72
20 POKE 65534, A

Additional Commands

RUN

The RUN is used to start the execution of Line-Numbered programs

10 PRINT "HELLO, WORLD!"
20 GOTO 10

RUN
HELLO, WORLD!
HELLO, WORLD!
HELLO, WORLD!
...

LIST

The LIST command is used to view the lines of uBASIC code that you have entered into the computer.

10 PRINT "HELLO, WORLD!"
20 FOR I = 1 TO 10
30   PRINT I
40 NEXT I

LIST 20

20 FOR I = 1 TO 10

LIST -30

10 PRINT "HELLO, WORLD!"
20 FOR I = 1 TO 10
30   PRINT I

LIST 30-40

30   PRINT I
40 NEXT I

LIST 20-

20 FOR I = 1 TO 10
30   PRINT I
40 NEXT I

NEW

The NEW command erases the content of uBASIC program memory

LIST
10 PRINT "HELLO, WORLD!"
READY.

NEW
READY.

LIST

READY.

FRE

The FRE command displays the remaining bytes available for the uBASIC program

FRE
2100 uBASIC BYTES FREE

Examples

Printing the alphabet to the terminal

REM SET VARIABLE A TO THE ADDRESS OF PORT A OUTPUT (PAO)
10 LET A = 65528
20 FOR I = 65 TO 90
30 POKE A, I | 128
40 POKE A, 0
50 NEXT I
60 POKE A, 10
70 POKE A, 0
80 END

Reading the timer value

REM CONFIGURE AND START THE TIMER IN ONE-SHOT MODE
10 LET C = 1
20 POKE 65535, C
30 PEEK 65534, T
40 PRINT T
50 GOTO 30

Odd-Even

When A equal to 6

10 LET A = 6
20 IF A % 2 = 0 THEN GOTO 50
30 PRINT "A IS ODD"
40 END
50 PRINT "A IS EVEN"
60 END

When A equal to 9

10 LET A = 9
...

Configuring uBASIC

Veecom uBASIC can be customized from the ubasic_config.h file.

Compiling and Building uBASIC

You'll need a RISC-V C/C++ compiler, I personally use this one for my windows machine.
Download and install risc-v-gcc10.1.0.exe and leave things to defaults.
Open the terminal, navigate to Veecom-uBASIC folder and type make.

From logisim load the final.bin file into Veecoms' main memory module.