Roadmap

The Big One (In Progress)

Ahead-of-Time Compiler (v0.15.0, Phase 1)

gwbasic-compile translates tokenized .bas programs to C source, then invokes GCC to produce native executables linked against libgwrt.a.

Pipeline: .bas → gw_crunch() → analysis pass → C codegen → gcc → native binary.

Phase 1: PRINT, LET, IF/THEN/ELSE, GOTO, GOSUB/RETURN, FOR/NEXT, END/STOP/SYSTEM, REM, DATA/READ/RESTORE, CLS, arithmetic, string functions, core math functions.

Phase 2 (current): WHILE/WEND, ON GOTO/GOSUB, ON ERROR GOTO, MOD/IDIV/POW operators (buffered left operand for proper casting), SWAP, POKE, DEF SEG, RANDOMIZE, LOCATE, COLOR, SCREEN, WIDTH, KEY, WRITE, OPTION BASE, DEF type statements, extended statement dispatch. DIM/array subscript access (gwrt_array_elem runtime), number formatting via gw_print_value() with expression type tracking, combined relational operators (<=, >=, <>), PRINT USING (token embedding with variable sync), STRING$/INSTR single-byte token support, PRINT USING (token embedding with variable sync), RESUME, ERROR, ON TIMER/KEY skip, MID$ assign skip, FOR scope fix (static limit/step), SWAP with array elements, ENVIRON$/ DATE$/TIME$/ENVIRON$ expression support, RESUME/ERROR statements, DEF FN (token embedding + variable sync), DEFINT/DEFSNG/DEFDBL/DEFSTR (pre-scan in analysis), gw_cint() rounding for integer assignment, STRING$(n,"c") string arg handling, READ into arrays, array assignment self-reference fix, PRINT USING colon-in-string. Zero compile errors — all 72 programs compile. 46 produce correct output (64%). String concatenation (A$+B$), READ into arrays, self-referencing array assignment fix, float division semantics, PRINT USING null-byte token fix, string comparison (strcmp), ON ERROR GOTO (setjmp), graphics/sound delegation to runtime via token embedding, CVI/MKI$/CVS/MKS$/CVD/MKD$, MID$ assignment delegation, ON ERROR GOTO with setjmp/gw_run_jmp, RESUME/RESUME NEXT, ERR/ERL, file I/O delegation (OPEN/CLOSE/PRINT#/ INPUT#/WRITE#/LINE INPUT via emit_delegate_stmt), PMAP/POINT/PSET graphics, BSAVE/BLOAD/SAVE/LOAD, MKDIR/CHDIR/RMDIR/KILL file ops. 64 produce correct output (89%). Division-by-zero detection, FIELD/GET variable read-back, CLS graphics flush, IOCTL$() handler. Only 5 failures remain: 3 structural (CHAIN/COMMON/RUN "file") and 2 RNG-dependent.

Phase 3: random-access files, PRINT USING, graphics, sound, event trapping, remaining statements.

Phase 4: optimizations (constant folding, integer fast paths, dead code).

Completed

Hardware I/O Simulator (v0.15.0)

Implemented in portio.c / portio.h following the virmem.c dispatch pattern. Emulates 8253 PIT channel 2 (speaker frequency), PPI port B (speaker on/off with continuous tone via PulseAudio), CGA mode/color registers, game port (joystick stub), and COM1 serial (transmitter-ready stub). Default: reads return 0xFF (floating bus), writes discarded.

Statements: OUT, WAIT, MOTOR. Functions: INP(), STICK(), STRIG().

Also in v0.15.0: filled remaining statement/function gaps — RESET, ENVIRON/ENVIRON$, ERDEV/ERDEV$, IOCTL/IOCTL$, LCOPY, DATE$/TIME$ assignment, CALL/CALLS, COM. All 144 defined tokens are now handled (100% token coverage).

String space pool with compacting garbage collector (strpool.c), replacing individual malloc/free. 32KB default pool, bump-pointer allocation, compaction at statement boundaries. FRE() returns actual free space; CLEAR n resizes the pool.

Jupyter Kernel (v0.15.0)

gwbasickernel/ — Jupyter notebook kernel using the persistent subprocess model. GW-BASIC reads BASIC from stdin in piped mode (no banner, no prompts, unbuffered stdout). Sentinel protocol (PRINT "<<<GWDONE>>>") delimits output per cell. State persists across cells.

Inline Sixel graphics — SCREEN 1/SCREEN 2 drawing commands render as inline PNG images in the notebook. Pure-Python Sixel decoder (no PIL or Ghostscript dependency).
INPUT statement support — when a program executes INPUT, the kernel requests input from the notebook front-end via the Jupyter stdin protocol.
Pygments syntax highlighting — GW-BASIC lexer registered as a Pygments entry point for code cell highlighting.
Tab completion for all GW-BASIC keywords.
Magic commands: %reset, %timeout, %new.

Install: pip install -e . && gwbasickernel-install --user

Next Up

IDE Integration

JetBrains plugin (IntelliJ/CLion) — full-featured language plugin with syntax highlighting, code completion, line number navigation, run configurations, debugger integration (breakpoints via STOP, variable inspection), structure view (line number outline), and error annotations.
VS Code extension — language extension providing syntax highlighting (TextMate grammar), snippets, run/debug tasks, integrated terminal runner, and Language Server Protocol support for diagnostics and hover info.

Known Limitations

Maximum 256 variables, 64 arrays, 16 FOR nesting, 24 GOSUB nesting, 16 WHILE nesting
CALL/CALLS (machine code execution) raises Illegal function call
DATE$/TIME$ assignment accepted but does not modify the system clock
Device stubs (ERDEV, IOCTL, COM, LCOPY) return defaults — no real device emulation

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