The VC-3 is a system, running on the SD-8516.
I guess this interrupt system is part of the KERNAL, so should be more “VC-3” as it is system software. What follows is a simple list of the interrupt, what it does, it's calling parameters and it's return codes. I guess this should be called “Stellar BIOS V1” or “VC-3 KERNAL ROM” could be a nice name.
Each INT subsystem has it's own convention. However, the INT 05h system was done first so it represents a general convention you can expect going forward.
LDAL #'A'
LDB #1234
LDAH $11 ; VAR_SET
INT $05
LDELD @string
LDAH $62 ; IO_GETNUM
INT $05
; B has parsed number
; PATB System Memory ($01ED00-$01EDFF, 256 bytes available)
.equ PATB_VARIABLES $01ED00 ; 26 vars × 2 bytes = 52 bytes ($01ED00-$01ED33)
.equ PATB_EXPR_STACK $01ED40 ; Expression stack, 64 bytes ($01ED40-$01ED7F)
.equ PATB_EXPR_SP $01ED80 ; Expression stack pointer (2 bytes)
.equ PATB_GOSUB_STACK $01ED82 ; GOSUB stack, 32 bytes (16 levels × 2 bytes)
.equ PATB_GOSUB_SP $01EDA2 ; GOSUB stack pointer (2 bytes)
.equ PATB_FOR_STACK $01EDA4 ; FOR stack, 40 bytes (8 levels × 5 bytes)
.equ PATB_FOR_SP $01EDCC ; FOR stack pointer (2 bytes)
.equ PATB_PROGRAM_PTR $01EDCE ; Current program line pointer (3 bytes)
.equ PATB_IL_PTR $01EDD1 ; Current IL instruction pointer (3 bytes)
.equ PATB_INPUT_PTR $01EDD4 ; Current input pointer (3 bytes)
.equ PATB_RANDSEED $01EDD7 ; Random seed (2 bytes)
.equ PATB_STATUS $01EDD9 ; Status flags (1 byte)
; Bit 0: Running (1) / Stopped (0)
; Bit 1: Error flag
; Bit 2: Break flag
.equ PATB_PROGRAM_BASE $030100 ; Start of program storage (Bank 3, offset $100)
.equ PATB_PROGRAM_END $03FFFF ; End (almost 64KB for programs)
; === EXECUTION CONTROL (AH=$00-$0F) === ; AH=$00: RUN_PROGRAM - Start execution from line number or beginning ; AH=$01: STOP_PROGRAM - Stop execution ; AH=$02: CONTINUE - Continue from current position ; AH=$03: EXEC_IL_STEP - Execute one IL instruction ; AH=$04: EXEC_IL_CONT - Execute IL until completion ; AH=$05: GET_STATUS - Get interpreter status ; AH=$06: SET_STATUS - Set interpreter status flags ; AH=$07: RESET_INTERP - Reset interpreter state ; ; === VARIABLE MANAGEMENT (AH=$10-$1F) === ; AH=$10: VAR_GET - Get variable value by letter ; AH=$11: VAR_SET - Set variable value by letter ; AH=$12: VAR_CLEAR_ALL - Clear all variables to 0 ; AH=$13: VAR_GET_ADDR - Get address of variable storage ; ; === EXPRESSION STACK (AH=$20-$2F) === ; AH=$20: EXPR_PUSH - Push value to expression stack ; AH=$21: EXPR_POP - Pop value from expression stack ; AH=$22: EXPR_PEEK - Peek at top of stack ; AH=$23: EXPR_CLEAR - Clear expression stack ; AH=$24: EXPR_DEPTH - Get current stack depth ; ; === PROGRAM LINE MANAGEMENT (AH=$30-$3F) === ; $30-$37: Search/Navigate ; $30: LINE_FIND - Find line by number (forward) ; $31: LINE_NEXT - Get next line ; $32: LINE_FIND_REVERSE - Find line by number (backward) ; $33: LINE_PREV - Get previous line ; $36-$39: Modify ; $36: LINE_INSERT - Insert or replace line ; $37: LINE_DELETE - Delete line by number ; $38: LINE_REMOVE_SPACE - Add space for new program line ; $39: LINE_MAKE_SPACE - remove unused line space ; $3A-$3F: Utility ; $3A: LINE_FIRST - Get first line ; $3B: LINE_CLEAR_ALL - Clear entire program (NEW) ; $3C: LINE_COUNT - Count total lines ; $3F: PROGRAM_END - ELM points to end of program ; ; === GOSUB/RETURN STACK (AH=$40-$4F) === ; AH=$40: GOSUB_PUSH - Push return address for GOSUB ; AH=$41: GOSUB_POP - Pop return address for RETURN ; AH=$42: GOSUB_CLEAR - Clear GOSUB stack ; ; === FOR/NEXT STACK (AH=$50-$5F) === ; AH=$50: FOR_PUSH - Push FOR loop context ; AH=$51: FOR_POP - Pop FOR loop context ; AH=$52: FOR_PEEK - Peek at current FOR loop ; AH=$53: FOR_CLEAR - Clear FOR stack ; AH=$54: FOR_FIND_VAR - Find FOR loop by variable letter ; ; === INPUT/OUTPUT HELPERS (AH=$60-$6F) === ; AH=$60: IO_GETCHAR - Get next character from input buffer ; AH=$61: IO_PUTCHAR - Output character to screen ; AH=$62: IO_GETNUM - Parse number from input ; AH=$63: IO_PUTNUM - Output number to screen ; AH=$64: IO_NEWLINE - Output CR/LF ; AH=$65: IO_GETLINE - Get line of input from user ; AH=$66: IO_PRINT_STR - Print string at pointer ; ; === STRING/TOKEN HELPERS (AH=$70-$8F) === ; 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 ; AH=$87-$8F: (Reserved for future string operations) ; ; === ARITHMETIC/LOGIC HELPERS (AH=$90-$9F) === ; AH=$90: MATH_ADD - Pop two values, push sum ; AH=$91: MATH_SUB - Pop two values, push difference ; AH=$92: MATH_MUL - Pop two values, push product ; AH=$93: MATH_DIV - Pop two values, push quotient ; AH=$94: MATH_NEG - Negate top of stack ; AH=$95: MATH_RND - Generate random number ; AH=$96-$9F: (Reserved) ; ; === COMPARISON HELPERS (AH=$A0-$AF) === ; AH=$A0: CMP_EQ - Compare equal ; AH=$A1: CMP_NE - Compare not equal ; AH=$A2: CMP_LT - Compare less than ; AH=$A3: CMP_GT - Compare greater than ; AH=$A4: CMP_LE - Compare less than or equal ; AH=$A5: CMP_GE - Compare greater than or equal ; AH=$A6-$AF: (Reserved) ; ; === ERROR HANDLING (AH=$B0-$BF) === ; AH=$B0: ERROR_SET - Set error flag and message ; AH=$B1: ERROR_GET - Get current error code ; AH=$B2: ERROR_CLEAR - Clear error flag ; AH=$B3: ERROR_PRINT - Print error message ; AH=$B4-$BF: (Reserved) ; ; === IL INTERPRETER CORE (AH=$F0-$FF) === ; AH=$F0: IL_INIT - Initialize IL interpreter ; AH=$F1: IL_LOAD - Load IL code into memory ; AH=$F2: IL_FETCH - Fetch next IL instruction ; AH=$F3: IL_DISPATCH - Dispatch IL instruction ; ============================================================================
; ============================================================================ ; INT 10h - VIDEO SERVICES ; Stellar BIOS Video interrupt handler ; ============================================================================ ; Function dispatch via AH register: ; AH=00h: Set video mode ; AH=01h: Set cursor shape (reserved) ; AH=02h: Set cursor position ; AH=03h: Get cursor position ; AH=0Eh: Write character at cursor (teletype) ; AH=0Fh: Get current video mode ; AH=13h: Write string at cursor ; AH=14h: Scroll screen up ; AH=15h: Clear screen ; AH=16h: Get video parameters (rows, cols) ; ============================================================================
Available modes: