Eremey Valetov
ad21350003
Authentic GW-BASIC screen editor with 25x80 buffer, free cursor movement, enter-on-any-line, F1-F10 function keys, Insert/Overwrite toggle, KEY ON/OFF/LIST statement, and Ctrl+Break handling. HAL pointer swap routes all PRINT/LIST/error output through the TUI automatically. Piped mode unchanged (50/50 tests pass). Adds automated compatibility testing infrastructure: DOSBox-X headless config, PRINT-to-file transform script, and run_compat.sh with --generate and --compare modes for verifying output against real GWBASIC.EXE. Project renamed from gwbasic-c to GW-BASIC 2026.
129 lines
4.3 KiB
Markdown
129 lines
4.3 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 | `$` | Up to 255 bytes |
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## Operators
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`+`, `-`, `*`, `/`, `^`, `\` (integer div), `MOD`, `AND`, `OR`, `XOR`, `EQV`,
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`IMP`, `NOT`, `<`, `=`, `>`, `<=`, `>=`, `<>`
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## Numeric Functions
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`SGN`, `INT`, `ABS`, `SQR`, `SIN`, `COS`, `TAN`, `ATN`, `LOG`, `EXP`, `RND`,
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`FIX`, `CINT`, `CSNG`, `CDBL`
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## String Functions
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`LEN`, `ASC`, `CHR$`, `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$`, `TIME$`
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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`, `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$` |
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| Program control | `RUN`, `RUN "file"`, `CONT`, `STOP`, `END`, `NEW`, `LIST`, `CLEAR` |
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| Sequential I/O | `OPEN`, `CLOSE`, `PRINT#`, `WRITE#`, `INPUT#`, `LINE INPUT#` |
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| Random-access I/O | `FIELD`, `LSET`, `RSET`, `PUT`, `GET`, `CVI`/`CVS`/`CVD`, `MKI$`/`MKS$`/`MKD$` |
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| Program I/O | `SAVE`, `LOAD`, `MERGE`, `CHAIN` |
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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` |
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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, `COMMON` |
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| System | `SYSTEM` |
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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 with free cursor movement (arrow keys)
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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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