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--- sd-8516_stellar_basic_v1.0 [2026/01/09 03:08] – appledog
+++ sd-8516_stellar_basic_v1.0 [2026/01/28 16:08] (current) – appledog
@@ Line 3: / Line 3: @@
 Dennis Allison’s 1975 article in Dr. Dobb’s Journal was a key moment in the history of Computer Science. It contained a formal specification of Tiny BASIC, a BASIC that could be implemented in less than 4 KB.
-Stellar BASIC is very much in the same vein as Tiny BASIC, and is intended to evolve over time.
+Stellar BASIC is very much in the same vein as Tiny BASIC, and is intended to evolve over time. However, Tiny BASIC itself is only a specification. One way is to compile a list of IL (intermediate language) statements. Once you have the IL interpretation you compile it and interpret it from there. On a machine with limited ram this approach can require up to 50% of the memory of a standard BASIC program. This is problematic. So machines like the C64 tokenized the statements on entry and executed them that way. The other issue with IL is that you have this compiled version and you also have the text lying around. That's two copies of the program. Which one is the 'real' program? If you remove the original text you can't necessarily LIST your code. Therefore, tokenization was settled on as a standard.
-== Core features
+Therefore, when it came time to compile the IL into a program we instead chose a C64 style tokenization, and added $99 as PRINT as a subtle homage to the adventure, the love, and the magic of the C64 era.
+== Core features
 * Line-numbered programs
 * ''LET'' (often optional)
-* `PRINT`
+* ''PRINT''
-* `INPUT`
+* ''INPUT''
-* `IF … THEN`
+* ''IF-THEN''
-* `GOTO`
+* ''GOTO''
-* `GOSUB` / `RETURN`
+* ''GOSUB'' and ''RETURN''
-* `FOR` / `NEXT`
+* ''FOR-NEXT''
-* Integer arithmetic only (usually 16-bit)
+* Usually only access to integer variables and integer based math
-* Single-letter variables (`A`–`Z`)
+* Single letter variables (ex. ''A'', ''B'', ''Z'')
-### What’s usually removed
 * No floating-point math
-* No strings (or very limited strings)
+* Very limited strings
-* No arrays (or extremely small ones)
+* No arrays
 * No file I/O
 * Minimal error messages
 * Very limited editing commands
-Some versions didn’t even store source code text—only tokenized forms.
+Some versions stored programs as text, some as tokenized program code to save space.
----
+== Example BASIC program
-## Size
+<Code:Basic>
-Typical Tiny BASIC interpreters:
-* **1–4 KB total**
-* Some famous versions were under **2 KB**
-* A few extreme versions fit in **less than 1 KB**
-This was achieved through:
-* Hand-written assembly
-* Tokenization
-* Shared code paths
-* Aggressive simplification of syntax
----
-## Example: Tiny BASIC program
-```basic
 LET A = 1
 PRINT A
@@ Line 56: / Line 36: @@
 IF A <= 10 THEN GOTO 20
 END
-```
+</Code>
-Many Tiny BASICs would allow this even shorter form:
+Stellar BASIC will allow this even shorter form:
-```basic
+<Code:Basic>
 A=1
 ?A
 A=A+1
 IF A<=10 GOTO 20
-```
+</Code>
-(`?` was often shorthand for `PRINT`.)
+(''?'' is shorthand for ''PRINT''.)
----
+== More Information
+Notable Tiny BASIC implementations
-## Notable Tiny BASIC implementations
 * **Palo Alto Tiny BASIC** (Dennis Allison)
@@ Line 80: / Line 59: @@
 * **Micro-Soft 8080 BASIC** (larger, but influenced by Tiny BASIC work)
-Each one differed slightly, but all followed the “tiny, usable, interactive” idea.
+== Appendix I: Pao Alto Tiny Basic
+Stellar Basic is based on Pao Alto Tiny Basic, written by Dennis Allison in 1975.
+=== Implementation
+Please see: https://www.helloneo.ca/wiki/doku.php?id=vc-3_system_interrupt_table#int_05h_-_pao_alto_tiny_basic
+I implemented it in this order:
+* Phase 1: Variable management (3 functions: get, set, clear_all)
+* Expression stack (4 functions: push, pop, peek, clear)
+* I/O & String Helpers (ex. IO_GETNUM)
+* String comparison, number parsing (ex. STR_SKIP_SPACE)
+* Phase 2: Stack Operations
+* GOSUB/RETURN stack (3 functions)
+* FOR/NEXT stack (4 functions)
+* Phase 3: Program Line Management
+* Find line by number
+* Insert/delete lines
+* Navigate through program (first line, next line)
+* Program storage with line markers (opcode 251)
----
+* Phase 4: IL Interpreter Core;
+* Design IL bytecode table (~30-40 IL opcodes)
+* Command tokenizer (major hurdles to pass -- this was hard)
+* IL fetch/decode/execute loop
+* Expression evaluation using the stack
+* Control flow (GOTO, GOSUB, IF/THEN, FOR/NEXT)
-## Why Tiny BASIC matters
+* Phase 5: BASIC Commands
+* PRINT, INPUT, LET
+* RUN, LIST, NEW, CLEAR
+* Integrate with term.ts to highlight a "Boot-to-basic" experience.
-Tiny BASIC is important because it:
+* Phase 6: Testing & Polish
+* End-to-end BASIC program tests
+* Error handling and status messages
+* Bug fixes
+* Performance tuning
-* Made programming accessible on the *cheapest possible hardware*
+=== Stack-based design
-* Helped bootstrap the early microcomputer software ecosystem
+Everything in PATB is stack-based. This is a core design principle. There are three stacks:
-* Demonstrated how interpreters could be **designed under extreme constraints**
-* Influenced later minimal languages and embedded scripting systems
-It’s often cited as an early example of **open, shared language design**, since many implementations were published openly in magazines.
+# **Expression Stack** - Arithmetic evaluation
+** "5 + 3 * 2" is "push 5", "push 3", "push 2", "multiply" (pop 2 values, push result), "add" (pop 2 values, push result).
+# **GOSUB Stack** - Subroutine calls
+** "GOSUB 1000" -- push current line number, jump to 1000
+** "RETURN" -- pop line number, jump back
+# **FOR Stack** - Loop context
+** "FOR I=1 TO 10" -- push (I, 10, 1)
+** "NEXT I" -- peek stack, increment I, check if done, pop if finished
----
+=== Immediate Modifications to PATB 1.0
+During the implementation phase I made several by-the-way changes to PATB in order to support a more advanced integration with the SD-8516. I added LINE_FIND_REVERSE and LINE_PREV as well as LINE_MAKE_SPACE and LINE_REMOVE_SPACE for line management. I am not sure how PATB does those things. I worked from example code and the specs but I did not really understand what I was doing. After the tests for the IL implementation passed I added string helpers. Some of these are in PATB (about 4 or 5 of them IIRC) but I added enough to support proper string handling, as it is the first thing I plan to add. After the basic port, of course.
-## In one sentence
+I'm really excited to start working on these because I feel I understand them and they will be easy. LINE_INSERT is not easy It is long and hard. I do not understand it... YET!
-> **Tiny BASIC is a deliberately minimal BASIC interpreter, typically fitting in a few kilobytes, designed to make interactive programming possible on the earliest and most constrained microcomputers.**
+* ;   AH=$70: STR_COMPARE    - Compare strings for keyword matching
+* ;   AH=$71: STR_TO_UPPER   - Convert string to uppercase
+* ;   AH=$72: STR_SKIP_SPACE - Skip whitespace in ELM string
+* ;   AH=$73: STR_IS_DIGIT   - Check if character is digit
+* ;   AH=$74: STR_IS_ALPHA   - Check if character is letter
+* ;   AH=$75: STR_LENGTH     - Get string length
+* ;   AH=$76: STR_COPY       - Copy string from src to dst
+* ;   AH=$77: STR_CONCAT     - Concatenate two strings
+* ;   AH=$78: STR_LEFT       - Extract left N characters (LEFT$)
+* ;   AH=$79: STR_RIGHT      - Extract right N characters (RIGHT$)
+* ;   AH=$7A: STR_MID        - Extract middle substring (MID$)
+* ;   AH=$7B: STR_CHR        - Convert byte to character (CHR$)
+* ;   AH=$7C: STR_ASC        - Convert character to byte (ASC)
+* ;   AH=$7D: STR_VAL        - Convert string to number (VAL)
+* ;   AH=$7E: STR_STR        - Convert number to string (STR$)
+* ;   AH=$7F: STR_FIND       - Find substring within string (INSTR)
+* ;   AH=$80: STR_LTRIM      - Trim leading whitespace
+* ;   AH=$81: STR_RTRIM      - Trim trailing whitespace
+* ;   AH=$82: STR_TRIM       - Trim both leading and trailing whitespace
+* ;   AH=$83: STR_REVERSE    - Reverse a string
+* ;   AH=$84: STR_REPEAT     - Repeat character N times (STRING$)
+* ;   AH=$85: STR_SPLIT      - Split string at delimiter
+* ;   AH=$86: STR_REPLACE    - Replace substring with another
-If you’d like, I can:
-* Show a **formal Tiny BASIC grammar**
-* Compare Tiny BASIC vs Microsoft BASIC
-* Explain how a Tiny BASIC interpreter works internally
-* Show how to write your own Tiny BASIC in C or assembly