Eremey Valetov
e7f35c21ff
Binary SAVE/LOAD: SAVE now writes tokenized binary by default (0xFF header format), matching original GW-BASIC behavior. SAVE "file",A for ASCII. LOAD auto-detects binary vs ASCII from the first byte. Command-line file loading also auto-detects, so binary .BAS files just work. INKEY$ extended keys: arrow keys, Home/End/PgUp/PgDn, Insert/Delete, and F1-F10 now return the correct CHR$(0) + scan_code two-byte sequences per the IBM PC convention. Refactored event trap key parsing to use tui_read_key() instead of duplicating escape sequence parsing. Golden-file regression tests: generated .expected output files for 55 of 58 test programs (3 timing-dependent tests excluded). The test runner now reports compat match status alongside pass/fail. Classic programs: added Hamurabi, Lunar Lander, Gunner, and Diamond from David Ahl's BASIC Computer Games (1978) in tests/classic/ for manual compatibility testing. Docs updated with compiler roadmap item and hardware I/O simulator plan.
229 lines
7.9 KiB
Markdown
229 lines
7.9 KiB
Markdown
# Language Reference
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## Data Types
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| Type | Suffix | Description |
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|------|--------|-------------|
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| INTEGER | `%` | 16-bit signed |
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| SINGLE | `!` | 32-bit float |
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| DOUBLE | `#` | 64-bit float |
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| STRING | `$` | Up to 255 bytes |
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## Operators
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`+`, `-`, `*`, `/`, `^`, `\` (integer div), `MOD`, `AND`, `OR`, `XOR`, `EQV`,
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`IMP`, `NOT`, `<`, `=`, `>`, `<=`, `>=`, `<>`
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## Numeric Functions
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`SGN`, `INT`, `ABS`, `SQR`, `SIN`, `COS`, `TAN`, `ATN`, `LOG`, `EXP`, `RND`,
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`FIX`, `CINT`, `CSNG`, `CDBL`
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`RND` can be called with or without parentheses: `RND` is equivalent to `RND(1)`.
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## String Functions
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`LEN`, `ASC`, `CHR$`, `VAL`, `STR$`, `LEFT$`, `RIGHT$`, `MID$`, `SPACE$`,
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`STRING$`, `HEX$`, `OCT$`, `INSTR`, `INPUT$`
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## File Functions
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`EOF`, `LOC`, `LOF`
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## Pseudo-variables
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`ERL`, `ERR`, `CSRLIN`, `INKEY$`, `DATE$`, `TIME$`, `TIMER`, `POS(0)`
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## Literals
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Decimal, `&H` hex, `&O` octal, `D` exponent (double), `E` exponent (single),
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type suffixes (`%`, `!`, `#`)
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## Statements
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| Category | Statements |
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|----------|------------|
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| Output | `PRINT`, `LPRINT`, `LLIST`, `PRINT USING`, `WRITE`, `CLS` |
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| Variables | `LET`, `DIM`, `ERASE`, `SWAP`, `DEFINT`, `DEFSNG`, `DEFDBL`, `DEFSTR` |
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| Control flow | `GOTO`, `GOSUB`/`RETURN`, `FOR`/`NEXT`, `IF`/`THEN`/`ELSE`, `WHILE`/`WEND`, `ON...GOTO`, `ON...GOSUB` |
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| Input | `INPUT`, `LINE INPUT`, `DATA`/`READ`/`RESTORE`, `INKEY$` |
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| Program control | `RUN`, `RUN "file"`, `CONT`, `STOP`, `END`, `NEW`, `LIST`, `CLEAR`, `AUTO`, `RENUM`, `DELETE`, `EDIT` |
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| Sequential I/O | `OPEN`, `CLOSE`, `PRINT#`, `WRITE#`, `INPUT#`, `LINE INPUT#` |
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| Random-access I/O | `FIELD`, `LSET`, `RSET`, `PUT`, `GET`, `CVI`/`CVS`/`CVD`, `MKI$`/`MKS$`/`MKD$` |
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| Program I/O | `SAVE` (binary/ASCII), `LOAD` (auto-detects), `MERGE`, `CHAIN`, `COMMON` |
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| Event trapping | `ON TIMER(n) GOSUB`, `TIMER ON`/`OFF`/`STOP`, `ON KEY(n) GOSUB`, `KEY(n) ON`/`OFF`/`STOP` |
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| Error handling | `ON ERROR GOTO`, `RESUME`, `RESUME NEXT`, `RESUME n`, `ERROR`, `ERR`, `ERL` |
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| User functions | `DEF FN`, `RANDOMIZE` |
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| File management | `KILL`, `NAME`, `FILES`, `MKDIR`, `RMDIR`, `CHDIR`, `SHELL` |
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| Date/time | `DATE$`, `TIME$`, `TIMER` |
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| Screen | `LOCATE`, `COLOR`, `WIDTH`, `SCREEN`, `KEY ON`/`OFF`/`LIST`, `KEY n,"string"` |
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| Graphics | `PSET`, `PRESET`, `LINE`, `CIRCLE`, `DRAW`, `PAINT` |
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| Sound | `SOUND`, `BEEP`, `PLAY` (MML parser, PulseAudio backend) |
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| Misc | `POKE`, `KEY`, `TRON`/`TROFF`, `OPTION BASE`, `MID$` assignment |
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| System | `SYSTEM` |
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## Program I/O (SAVE / LOAD)
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`SAVE` writes the current program to a file. The default format is tokenized
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binary (compact, fast to load), matching the original GW-BASIC behavior:
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```
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SAVE "myprog.bas" ' tokenized binary (default)
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SAVE "myprog.bas",A ' ASCII text (human-readable, editable)
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```
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`LOAD` reads a program file, auto-detecting the format from the first byte:
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```
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LOAD "myprog.bas" ' auto-detects binary or ASCII
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LOAD "myprog.bas",R ' load and run immediately
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```
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Binary files use the standard GW-BASIC 0xFF header format. Command-line
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loading (`./gwbasic file.bas`) also auto-detects format.
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`MERGE` loads an ASCII file without clearing the current program, overlaying
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lines by number. `CHAIN` loads and runs a new program, optionally preserving
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variables listed by `COMMON`.
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## INKEY$ Extended Keys
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`INKEY$` returns a zero-length string when no key is available, a one-byte
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string for regular ASCII keys, or a two-byte string for extended keys:
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```
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K$ = INKEY$
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IF LEN(K$) = 2 THEN scan = ASC(MID$(K$, 2, 1))
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```
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Extended keys return `CHR$(0)` as the first byte and the IBM PC scan code
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as the second. Common scan codes:
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| Key | Scan | Key | Scan |
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|-----|------|-----|------|
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| F1-F10 | 59-68 | Home | 71 |
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| Up | 72 | PgUp | 73 |
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| Left | 75 | Right | 77 |
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| End | 79 | Down | 80 |
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| PgDn | 81 | Ins | 82 |
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| Del | 83 | | |
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## Printer Output (LPRINT / LLIST)
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`LPRINT` works identically to `PRINT` but sends output to the printer:
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- **Default:** output is appended to `LPT1.TXT` in the current directory
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- **`--lpt /dev/lp0`** (Linux) or **`--lpt LPT1`** (FreeDOS): send to real hardware
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- **`--lpt report.txt`**: redirect to a custom file
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`LLIST` lists the program to the printer, with optional line number ranges
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(`LLIST`, `LLIST 10-50`, `LLIST -100`).
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Both support `PRINT USING`, semicolons, commas, `TAB()`, and `SPC()`.
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## Graphics
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Graphics mode is activated with `SCREEN 1` (320x200, 4 colors) or
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`SCREEN 2` (640x200, monochrome). Drawing commands render to an internal
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framebuffer and output via [Sixel graphics](https://en.wikipedia.org/wiki/Sixel),
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which works in terminals like xterm, mlterm, foot, and WezTerm.
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### Drawing Commands
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- `PSET (x,y), color` / `PRESET (x,y)` — set/reset individual pixels
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- `LINE (x1,y1)-(x2,y2), color [,B|BF]` — lines, boxes, filled boxes
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- `CIRCLE (cx,cy), r [,color [,start, end [,aspect]]]` — circles and arcs
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- `PAINT (x,y), fill, border` — flood fill
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- `DRAW string` — turtle graphics mini-language (U/D/L/R/E/F/G/H, M, C, S, B, N)
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- `POINT (x,y)` — read pixel color
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- `COLOR fg, bg` — set foreground/background colors
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### Example
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```
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SCREEN 1
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LINE (0,0)-(319,199), 1
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CIRCLE (160,100), 80, 2
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PAINT (160,100), 3, 2
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```
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## Sound
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- `SOUND frequency, duration` — play a tone (frequency in Hz, duration in clock ticks)
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- `BEEP` — play the default beep
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- `PLAY string` — Music Macro Language (MML) string for melodies
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Sound output uses PulseAudio when available; commands are silently ignored otherwise.
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## Full-Screen Editor (TUI)
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When running interactively, GW-BASIC 2026 presents the authentic full-screen
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editor:
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- 25×80 screen buffer by default, or full terminal size with `--full`
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- Press Enter on any screen line to re-enter it as BASIC input
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- Insert/Overwrite toggle (Insert key)
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- Home/End/Delete/Backspace/Escape for line editing
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- Ctrl+C interrupts running programs
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- Uses the ANSI alternate screen buffer for clean terminal restore on exit
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### Function Keys
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Default F1-F10 bindings match the original GW-BASIC:
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| Key | Default | Key | Default |
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|-----|---------|-----|---------|
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| F1 | `LIST ` | F6 | `,"LPT1:"` + Enter |
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| F2 | `RUN` + Enter | F7 | `TRON` + Enter |
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| F3 | `LOAD"` | F8 | `TROFF` + Enter |
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| F4 | `SAVE"` | F9 | `KEY ` |
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| F5 | `CONT` + Enter | F10 | `SCREEN 0,0,0` + Enter |
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- `KEY ON` — show the function key bar on line 25
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- `KEY OFF` — hide the bar
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- `KEY LIST` — display all definitions
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- `KEY n, "string"` — redefine a function key
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### Piped Mode
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When stdin is not a terminal (piped input), the TUI is not activated.
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The interpreter reads lines from stdin and writes output directly to stdout,
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suitable for scripting and test harnesses.
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### Program Editing
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- `EDIT [linenum]` — display a program line for editing in the TUI; press Enter to re-store it
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- `AUTO [start][,increment]` — automatic line numbering mode
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- `RENUM [new][,[old][,increment]]` — renumber program lines (patches all GOTO/GOSUB references)
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- `DELETE range` — delete program lines (`DELETE 10-50`, `DELETE -100`, `DELETE 200-`)
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## Event Trapping
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GW-BASIC supports event-driven programming through trap handlers that fire
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between statements during program execution.
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### Timer Events
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```
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ON TIMER(n) GOSUB line ' register handler (fires every n seconds)
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TIMER ON ' enable timer trapping
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TIMER STOP ' suspend trapping (events are queued)
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TIMER OFF ' disable trapping (events are discarded)
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```
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### Function Key Events
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```
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ON KEY(n) GOSUB line ' register handler for F-key n (1-10)
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KEY(n) ON ' enable trapping for key n
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KEY(n) STOP ' suspend trapping (events are queued)
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KEY(n) OFF ' disable trapping
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```
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Event handlers execute as implicit GOSUBs. The `RETURN` statement returns
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to the interrupted code and clears the handler's in-progress flag. Events do
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not fire inside their own handler (re-entrant protection).
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`TIMER STOP` / `KEY(n) STOP` queue events while stopped; switching to
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`TIMER ON` / `KEY(n) ON` fires the pending event immediately.
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