da1e6cebf1
- .github/workflows/ci.yml: the dos-cross-compile job failed on the first push because build_dos.sh sources $HOME/openwatcom-v2/setvars.sh if WATCOM is unset, but that file isn't part of the OpenWatcom V2 snapshot — I'd been creating it locally by hand. Add a "Configure OpenWatcom env" step that generates setvars.sh after extraction (so build_dos.sh works) AND exports WATCOM/PATH/INCLUDE via $GITHUB_ENV (so subsequent steps work even if setvars.sh sourcing changes). Also stash both DOS binaries before the next-mode clean wipes them, so the artifact upload actually has both .exe files. - src/codegen.c: switch the four remaining emit_str_atom callers (CVI/CVS/CVD function args + string-comparison left/right) to emit_str_expr. Now `CVS(A$+B$)` and `A$+B$ < C$` accept concatenation in their string operands; previously the atom-level caller stopped at the first identifier and the trailing `+` confused downstream parsing. Verified: CVS(MKS$(3.14)+MKS$(0)) round-trips to 3.14 in both interpreter and compiled binary. All 72 interpreter + 63 compiler tests still pass. - docs/getting-started.md: document that gwbasic-compile auto-numbers unnumbered direct-mode lines (last_num + 10) so scratchpad-style programs compile without manual renumbering. - tests/run_freedos_qemu.sh: helper for going through the manual TUI checklist on bare FreeDOS. Modern qemu-kvm doesn't expose -fda on the default machine type and fat:rw: protocol is gone, so a fully automated FreeDOS smoke isn't tractable from userspace; this script builds a FAT data image (mtools), attaches it as -hdb to the FreeDOS qcow2, and points the user at the manual sequence in the script header. The DOSBox-X harness (run_dos_smoke.sh) remains the automated DOS smoke.
GW-BASIC 2026
A portable C reimplementation of Microsoft GW-BASIC, using the original 8088 assembly source (released by Microsoft in 2020) as the authoritative reference.
This is not a transpilation -- it reimplements the algorithms in clean C11 with modern data structures while targeting bug-compatible behavior.
Building
cmake -B build && cmake --build build
Requires a C11 compiler and CMake 3.10+. PulseAudio (libpulse-simple)
is optional -- detected at build time for SOUND/BEEP/PLAY support.
Builds three targets:
gwbasic-- the interpretergwbasic-compile-- the ahead-of-time compilerlibgwrt.a-- runtime library for compiled programs
Usage
Interactive mode launches the authentic GW-BASIC full-screen editor:
$ ./gwbasic
GW-BASIC 2026 0.17.0
(C) Eremey Valetov 2026. MIT License.
Based on Microsoft GW-BASIC assembly source.
Ok
PRINT 2+2
4
Ok
Run a program file (ASCII or binary tokenized):
./gwbasic tests/programs/prime_sieve.bas
Compile to a native executable:
./gwbasic-compile tests/programs/fibonacci.bas -c --runtime .
Ahead-of-Time Compiler
gwbasic-compile translates BASIC programs to C source, then invokes GCC
to produce native executables linked against libgwrt.a.
Pipeline: .bas → tokenizer → analysis → C codegen → gcc → native binary.
63 of 63 eligible test programs compile via gwbasic-compile and produce
output matching the interpreter's golden files. Run bash tests/run_compiler_tests.sh to verify.
# Generate C source
./gwbasic-compile myprog.bas -o myprog.c
# Compile to executable (automatic)
./gwbasic-compile myprog.bas -c --runtime /path/to/gw-basic-2026
Jupyter Kernel
A Jupyter notebook kernel for GW-BASIC with inline Sixel graphics rendering, INPUT support, and Pygments syntax highlighting.
pip install -e .
gwbasickernel-install --user
jupyter notebook # select "GW-BASIC 2026" kernel
What Works
100% token coverage -- all 144 GW-BASIC tokens are implemented.
Data types: INTEGER (%), SINGLE (!), DOUBLE (#), STRING ($)
Operators: + - * / ^ \ MOD AND OR XOR EQV IMP NOT < = > <= >= <>
Statements:
| Category | Statements |
|---|---|
| Output | PRINT, LPRINT, LLIST, PRINT USING, WRITE, CLS |
| Variables | LET, DIM, ERASE, SWAP, DEFINT/SNG/DBL/STR |
| Control flow | GOTO, GOSUB/RETURN, FOR/NEXT, IF/THEN/ELSE, WHILE/WEND, ON...GOTO/GOSUB |
| Input | INPUT, LINE INPUT, DATA/READ/RESTORE, INKEY$ |
| Program | RUN, CONT, STOP, END, NEW, LIST, CLEAR, AUTO, RENUM, DELETE, EDIT |
| Sequential I/O | OPEN, CLOSE, PRINT#, WRITE#, INPUT#, LINE INPUT# |
| Random-access I/O | FIELD, LSET, RSET, PUT, GET, CVI/CVS/CVD, MKI$/MKS$/MKD$ |
| Program I/O | SAVE (binary/ASCII), LOAD (auto-detects), MERGE, CHAIN, COMMON |
| Event trapping | ON TIMER(n) GOSUB, TIMER ON/OFF/STOP, ON KEY(n) GOSUB |
| Error handling | ON ERROR GOTO, RESUME, ERROR, ERR, ERL |
| User functions | DEF FN, RANDOMIZE |
| File management | KILL, NAME, FILES, MKDIR, RMDIR, CHDIR, SHELL, ENVIRON |
| Date/time | DATE$, TIME$, TIMER |
| Screen | LOCATE, COLOR, WIDTH, SCREEN, KEY ON/OFF/LIST |
| Graphics | PSET, PRESET, LINE, CIRCLE, DRAW, PAINT, GET/PUT (sprites), VIEW, WINDOW, PALETTE, PMAP |
| Sound | SOUND, BEEP, PLAY (MML) |
| Memory | DEF SEG, PEEK, POKE, BSAVE, BLOAD |
| Hardware I/O | OUT, INP, WAIT, MOTOR, STICK, STRIG |
Tests
72 interpreter tests, 14 kernel tests, 63 compiler tests -- all passing.
bash tests/run_tests.sh # interpreter
python -m gwbasickernel.test_kernel # Jupyter kernel
DOS / FreeDOS
Cross-compiles to DOS with OpenWatcom V2:
wmake -f Makefile.dos16 # 16-bit real-mode (128KB standalone, no extender)
wmake -f Makefile.dos # 32-bit DOS/4GW (175KB, requires DOS4GW.EXE)
The 16-bit build runs on FreeDOS, MS-DOS, and compatible systems without a DOS extender. See Getting Started for details.
Documentation
Full Sphinx documentation in docs/:
cd docs && pip install -r requirements.txt && make html
License
MIT License. See LICENSE.