READ into array elements: parse subscripts after variable name in READ
handler, call gwrt_array_elem + gwrt_data_read. Unlocks matrix_mult,
roman_numerals (partial).
PRINT USING colon-in-string: scan past quoted strings when finding
statement-end colon for token embedding. Fixes truncated format strings
like "Pi estimate: #.####".
Array element assignment: don't zero element before RHS evaluation.
Previous code did `*_elem = {.type=4}` which zeroed fval before
reading C(I,J) in `C(I,J) = C(I,J) + A(I,K)*B(K,J)`, making
self-referencing assignments always read 0.
DEF FN call fix: skip past TOK_FN byte before calling gw_eval_fn_call.
DEFINT pre-scan: analysis pass processes DEFINT/DEFSNG/DEFDBL/DEFSTR
before variable type resolution.
Integer assignment rounding: use gw_cint() (rint) instead of (int16_t)
C truncation.
41/72 tests pass. 0 compile errors.
New: hundred_doors, matrix_mult, pascal_triangle, stats_calc.
PRINT USING: embed token bytes in generated C and call gw_print_using()
at runtime. Variable values synced to interpreter table before the call
so gw_eval() can resolve them. Unlocks fibonacci, temp_table, calendar.
STRING$ (single-byte token 0xD4): handle in emit_str_expr and PRINT
string detection. Emits gw_fn_strings() call.
INSTR (single-byte token 0xD6): handle in emit_atom with start position
detection. Emits gw_fn_instr() call.
PRINT USING token skip fix: skip past TOK_USING before embedding bytes
(gw_print_using expects text_ptr after USING, not at it).
27 of 72 tests now pass. New: fibonacci, calendar, temp_table.
Array name emission: use emit_name_str() to avoid null bytes in C string
literals when variable name has only one significant character.
Combined relationals: handle <=, >=, <> token pairs (TOK_LT+TOK_EQ etc.)
in the precedence climber. Previously these emitted "unknown tok 0xe5"
which broke WHILE X <= 10 and similar conditions.
Expression type tracking: peek_expr_type() determines VT_INT/VT_SNG/VT_DBL
from the leading token in PRINT expressions. PRINT now emits the correct
gw_value_t type for proper number formatting (single vs double precision).
23 of 72 tests now pass (up from 19). New: arrays, hailstone, while_wend,
prime_sieve, leibniz.
Arrays: DIM creates arrays via gwrt_dim() runtime call. Array element
read/write uses gwrt_array_elem() with buffered subscript expressions
(open_memstream) to correctly determine dimension count. Auto-DIM with
default size 10 for undeclared arrays.
Number formatting: PRINT now uses gw_print_value() (same as interpreter)
instead of gwrt_print_sng(), producing correct type-specific output.
OPEN fix: analysis pass skips OPEN statement arguments to avoid
misidentifying OUTPUT/INPUT/APPEND as variable names.
OPEN/CLOSE/INPUT: emit skip stubs (file I/O compilation is Phase 3).
19 of 72 tests now pass (up from 17). New: hanoi, text_adventure.
Add WHILE/WEND, ON n GOTO/GOSUB, ON ERROR GOTO, DIM (stub), SWAP,
POKE, DEF SEG, RANDOMIZE, COLOR, LOCATE, SCREEN, WIDTH, KEY, WRITE,
OPTION BASE, DEFINT/DEFSNG/DEFDBL/DEFSTR, TRON/TROFF.
Fix MOD/IDIV/POW operators: buffer left operand via open_memstream so
both sides can be properly cast (MOD/IDIV → int16_t, POW → pow()).
Previously MOD on float operands was a C compile error.
Handle all extended statement tokens (0xFE prefix): graphics, sound,
file I/O, view/window, environ, timer — either with real codegen or
graceful skip.
17 of 72 tests now pass (up from 15). 26 compile errors (down from 30).
- FOR/NEXT: use a FOR stack to match NEXT variables to their corresponding
FOR labels, fixing nested loops (e.g., FOR I...FOR J...NEXT J...NEXT I)
- Remove unused emit_int_expr function
- Build now zero warnings across all targets
- Compiler passes 15 of 72 test programs (Phase 1 target: ~30)
- codegen.c: refactor one-liner function cases to proper multi-line blocks,
eliminating all -Wmisleading-indentation warnings
- codegen.c: escape quotes and backslashes in DATA pool string literals
- codegen.c: guard NEXT against for_label_counter=0 (NEXT without FOR)
- codegen.c: remove unused functions (emit_expr, read_sng, read_dbl)
- analysis.c: add bounds check on data_line_map writes
- Build now produces zero warnings across all three targets
- FRE(): remove strpool_gc() call during expression evaluation — temporaries
on the C stack would become dangling pointers after compaction
- WAIT: reject mask=0 (would infinite-loop since AND 0 is always 0)
- ENVIRON: use setenv()+free() instead of putenv() to avoid memory leak
and dangling pointer if pool is compacted
- portio: add bounds check to com1_inp() (com1_out already had one)
- kernel: use CHR$(1) sentinel prefix to avoid collision with user output
- kernel: fix INPUT prompt rfind() edge case when no newline in buffer
- eval.c: enlarge DATE$ format buffer to silence -Wformat-truncation
Sixel graphics: pure-Python decoder extracts ESC P...ESC \ sequences from
the output stream, renders RGBA pixels, and encodes as PNG for inline
display in the notebook. No external dependencies (no PIL, no Ghostscript).
INPUT support: when gwbasic prints "? " (INPUT prompt), the kernel uses
the Jupyter stdin protocol (raw_input) to request input from the user and
feeds the response back to the subprocess.
Pygments lexer (basic_lexer.py): GW-BASIC syntax highlighting with line
numbers, keywords, builtins, string/number literals, and comments.
Registered as a Pygments entry point and referenced in kernel language_info.
Test suite expanded from 10 to 14 tests (Sixel decode, PNG encode, inline
graphics integration, lexer tokenization).
Persistent subprocess model: gwbasic reads BASIC from stdin and writes
output to stdout in piped mode (no banner, no prompts, unbuffered).
Sentinel protocol (PRINT "<<<GWDONE>>>") delimits output per cell.
Features: state persistence across cells, error detection and reporting,
tab completion for GW-BASIC keywords, %reset/%timeout/%new magic
commands, Ctrl+C forwarding, automatic process restart.
Includes setup.py for pip install, kernel.json spec, install script,
and 10-test smoke suite (all passing).
Replaces individual malloc/free string management with a contiguous pool
(default 32KB) and compacting GC, matching the original GW-BASIC's
GETSPA/GARBAG architecture. Allocation is a bump pointer; gw_str_free()
is a no-op (descriptors are nulled, data reclaimed by GC). Compaction
runs at statement boundaries when the pool drops below 4KB free, walking
the variable table and array storage to relocate live strings.
FRE() now returns actual free pool space. FRE("") triggers a GC pass
before reporting. CLEAR n sets the string space size.
Closes the last unimplemented extended statement tokens. ENVIRON uses
putenv/getenv for real environment variable access. DATE$/TIME$
assignment is accepted but silently ignored (no system clock modification).
ERDEV/ERDEV$/IOCTL$/PEN return stub values (no real device hardware).
CALL/CALLS raise Illegal function call. COM event trapping silently
accepted.
New portio.c module following the virmem.c dispatch-by-address pattern,
emulating 8253 PIT channel 2 (speaker frequency), PPI port B (speaker
on/off), CGA mode/color select registers, game port (joystick stub),
COM1 serial (transmitter-ready stub), and floating bus default (0xFF).
OUT/WAIT/MOTOR statements and INP()/STICK()/STRIG() functions now fully
functional. Continuous tone generation via PulseAudio pthread worker for
programs that drive the speaker through OUT &H43/&H42/&H61.
Rewrites gfx_draw() as a recursive draw_engine() to support all DRAW
mini-language features:
Bug fixes:
- M command parsing: skip generic arg parser so M100,50 correctly
parses both coordinates instead of consuming x as a generic arg
- S (scale) semantics: distance is now (arg ?: 1) * scale / 4, matching
original GW-BASIC where S4 means 1 pixel per unit, not 4
- A (rotation): implements 90-degree rotation state with direction
vector transform for all 8 direction commands
New features:
- TA n: arbitrary rotation angle (-360 to 360 degrees) via cos/sin
- =variable;: numeric variable substitution in DRAW strings
- X stringvar;: execute substring from string variable (recursive)
- Scale factor applied to relative M coordinates
Binary tokenized SAVE/LOAD now stores float constants in Microsoft Binary
Format (MBF) on disk, matching original GWBASIC.EXE. A token-walking function
(convert_floats) converts IEEE↔MBF at the save_binary()/load_binary() boundary.
Also fixes a latent bug where load_binary() scanned for 0x00 to find the end
of each token line — this fails when float bytes contain null (e.g. MBF for
100.5 is 00 00 49 87). The loader now uses the next-line pointer to compute
token data length, matching the original's approach.
Expand roadmap with detailed implementation plans for the next three
features: MBF binary file compatibility (token-stream conversion at
load/save boundary), hardware I/O simulator (portio.c with PIT/speaker/
CGA/joystick port emulation), and DRAW command fixes (M parsing bug,
scale semantics, A rotation, TA/variable substitution). Remove hardware
I/O from known limitations (moving to planned). Fix stale test counts
(64 -> 66) and version string (0.11.0 -> 0.13.0) across docs.
Apply coordinate mapping (VIEW/WINDOW) to POINT(x,y) function so it
returns correct pixel values when WINDOW is active. Remove unused
palette[] array from graphics.c (Sixel encoder uses palette_map[]
directly). Expand view_window.bas test to cover WINDOW SCREEN mode,
VIEW+WINDOW combination, and PMAP inverse mapping. Fix CI test count
in docs.
BSAVE/BLOAD: save and load virtual memory blocks with 0xFD-header
binary format, operating on the current DEF SEG segment.
TUI color: tui_refresh emits ANSI SGR codes from cell attributes;
COLOR statement sets tui.current_attr when TUI is active.
Extended PEEK/POKE: CGA graphics framebuffer (interlaced layout) via
gfx_cga_peek/poke routed through virmem when gfx_active(); BIOS
keyboard shift flags (offset 0x17 bit 7 = insert mode).
Add bibliography to language reference. 64 tests, all passing.
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$(0) + scan_code two-byte sequences per
the IBM PC convention. Refactored event trap key parsing to use tui_read_key()
instead of duplicating escape sequence parsing.
Golden-file regression tests: generated .expected output files for 55 of 58
test programs (3 timing-dependent tests excluded). The test runner now
reports compat match status alongside pass/fail.
Classic programs: added Hamurabi, Lunar Lander, Gunner, and Diamond from
David Ahl's BASIC Computer Games (1978) in tests/classic/ for manual
compatibility testing.
Docs updated with compiler roadmap item and hardware I/O simulator plan.
Add event-driven programming: ON TIMER(n) GOSUB with TIMER ON/OFF/STOP,
ON KEY(n) GOSUB with KEY(n) ON/OFF/STOP for F1-F10. Fix F-key escape
sequence parser (F9/F10 detection, push back consumed bytes on unmatched
sequences). Add EDIT statement for TUI line editing. Guard key trap
polling so keystrokes aren't consumed when no traps are configured.
RND can now be called without parentheses (equivalent to RND(1)),
matching real GW-BASIC behavior for legacy code compatibility.
Update all Sphinx documentation pages to reflect features added in
v0.6.0-0.8.0: DATE$/TIME$/TIMER, FILES/SHELL/CHDIR/MKDIR/RMDIR,
AUTO/RENUM/DELETE, COMMON, LPRINT/LLIST with --lpt, --full TUI flag,
dynamic screen buffer, 54 tests.
LPRINT and LLIST now output to a printer device or file instead of the
screen. By default, output is appended to LPT1.TXT in the current
directory. Use --lpt to redirect to a real printer device (/dev/lp0,
LPT1 on FreeDOS) or a custom file path.
Includes full PRINT format support (semicolons, commas, TAB, SPC,
PRINT USING) and LLIST with line number range parsing.
The Ubuntu package index on GitHub runners was stale, causing 404s for
libglib2.0 (a transitive dependency of libpulse-dev). Also make the
install non-fatal since PulseAudio is optional.
The TUI screen buffer is now dynamically allocated instead of using a
fixed 25x80 array. When launched with --full/-f, the editor queries the
terminal size via ioctl(TIOCGWINSZ) and adapts accordingly. The default
remains the authentic 25x80.
AUTO generates line numbers during interactive editing, RENUM
renumbers program lines and patches all GOTO/GOSUB/ON references,
DELETE removes line ranges. COMMON declares variables preserved
across CHAIN. Also fixed LIST/DELETE range parsing (was broken by
expression evaluator consuming the dash as subtraction).
Bump to v0.7.0, 53 tests.
DATE$, TIME$, and TIMER now return real system date/time instead of
hardcoded values. Added directory and shell access statements with
proper GW-BASIC error codes (Path not found 76, File already exists 60).
Bump to v0.6.0, 52 tests.
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.
Eremey Valetov