Four roadmap items:
- codegen: fix parenthesized string comparison. emit_atom didn't
consume the body of a string-literal token (`"`), so for
PRINT (A$+B$ < "ZZZ") it emitted a 0 placeholder, advanced one byte,
and left "ZZZ" to be reparsed as a variable + extra trailing tokens
-- the binary then failed to link with `var_ZZ_sng` undeclared.
emit_atom now skips to the closing quote. Separately, the
left_type tracking in emit_num_prec dropped VT_STR after a string +
string concat (becoming VT_SNG), so the string-comparison codepath
skipped when the relational operator arrived. Preserve VT_STR
through TOK_PLUS when both operands are strings. Verified: paren
string-cmp now compiles and produces the same -1 / 0 result as the
interpreter.
- compiler: --no-gc-check and --fast-math optimization flags.
--no-gc-check skips the per-line gwrt_check_line() (no string-pool
GC, no Ctrl+Break trap). --fast-math drops the divide-by-zero
guard on `/`; the divisor still goes through (double) so 10/0
produces inf rather than SIGFPE. Both threaded through
codegen_opts_t and exposed in --help. --inline-arrays from the
roadmap deferred -- larger refactor.
- interp: raise static caps on 32-bit / Linux builds. vars 256
-> 1024, arrays 64 -> 256, MAX_FOR_DEPTH 16 -> 64, MAX_GOSUB_DEPTH
24 -> 128, MAX_WHILE_DEPTH 16 -> 64. Codegen FOR_STACK_MAX 16
-> 64. Analysis-pass caps: MAX_LINES 4096 -> 8192, MAX_VARS 256
-> 1024, MAX_GOTOS 256 -> 1024, MAX_DATA 1024 -> 4096,
MAX_GOSUB_RET 256 -> 1024. 16-bit DOS keeps the original modest
caps via #ifdef _M_I86 -- the MEDIUM model has a single 64KB
DGROUP for all static data and the bumped sizes broke runtime
startup under DOSBox-X. 16-bit binary grew from 128KB to 132KB
from the offset_secs field plus DATE$/TIME$ shift code, well
within the FreeDOS budget.
- interp + codegen: DATE$ / TIME$ assignment via process-local
clock offset. Was a no-op accept-and-ignore. Now sets
gw.time_offset_secs (long), and DATE$ / TIME$ / TIMER readers
apply it to time(NULL) before formatting. The OS clock is
unaffected (would need root). Compiled-binary readers also
reference gw.time_offset_secs since libgwrt shares the gw
struct. Verified: PRINT DATE$; DATE$="12-31-1999"; PRINT DATE$
shows the expected before/after in both interpreter and AOT
paths.
After these changes: 72/72 interpreter tests, 68/68 compat, 63/63
compiler tests, DOS smoke under DOSBox-X all pass. Build clean on
both Linux (cmake) and 16-bit DOS (build_dos.sh 16).
QA findings from a multi-round review of the FreeDOS submission prep work:
- TUI rendering refactor: src/tui.c emitted ANSI escape sequences via
printf, which displays as raw text on bare FreeDOS (no ANSI.SYS).
Add four HAL ops (tui_enter, tui_leave, render_run, set_cursor_shape)
and route per-cell rendering through them. POSIX backend keeps the
ANSI path; DOS backend drives BIOS INT 10h via the existing
bios_set_cursor / bios_write_char helpers. The TUI's logical cursor
goes through the saved orig_locate to avoid recursing through the
swapped-in gw_hal->locate.
- DOS extended-key mapping: dos_getch returns 0x100 | scancode for
arrows / F-keys; tui_read_key wasn't translating those to its TK_*
constants, so the editor never saw arrow keys or F1-F10 on DOS.
Add a __MSDOS__-conditional translation table in tui_read_key.
- Version banner: GW_VERSION was still 0.16.0 even though the v0.17.0
release prep was already in CHANGES.TXT. Bump.
- Compiler PulseAudio link: gwbasic-compile -c hardcoded
'-lgwrt -lm -lpthread' on the gcc command line. When libgwrt was
built against libpulse-simple (the default on any host with the
PulseAudio dev headers installed), the compile workflow failed with
'undefined reference to pa_simple_drain'. CMake now passes
GWRT_HAS_PULSEAUDIO to gwbasic-compile when libpulse is present, and
the compiler appends -lpulse-simple to the link line.
- FRE("") garbage collection: the interpreter skipped strpool_gc with a
comment 'unsafe during expression eval', but that's exactly what real
GW-BASIC's FRE("") does (and the AOT compiler path already did). Add
the GC call; strpool_pin/unpin is the existing escape hatch if a
caller has live pool pointers on the C stack. Fixes the string_gc
compat test.
- Test harness normalization: run_tests.sh stripped trailing whitespace
on the actual output but not the expected file, causing spurious
mismatches against golden files captured from real GWBASIC.EXE.
Normalize both sides identically. Fixes the peek_gfx mismatch.
- Print_using: snprintf into mantissa[32] with %.*f and an unbounded
dec triggered a -Wformat-truncation warning. Clamp dec to 20 (IEEE
double has at most ~17 significant decimal digits).
- Doc/version consistency: 16-bit binary size reported as 127KB in one
place and 128KB in three; standardize on 128KB. HAL backend count
said '1 file' but is now 2. CI test count said 'all 66 test
programs' but is 72. Add a v0.17.0 row to the development.md table.
Update getting-started.md DOS section to match the BIOS-rendering
reality and add a manual TUI verification checklist.
- dos_init now writes back BIOS-reported cols/rows to dos_hal struct
fields (forward-declared so dos_init can reference it).
After these changes: 72/72 interpreter tests pass, compat 68/68
matched, no warnings on the Linux build.
The 4KB screen buffer (80x25x2 bytes) was allocated from near heap via
calloc(), which exhausted the 64KB data segment on 16-bit DOS. Now uses
_fcalloc()/_ffree() from OpenWatcom's far heap on 16-bit, keeping the
buffer outside DGROUP.
The TUI now works fully on 16-bit FreeDOS: full-screen editor, F-key
bar, cursor positioning, and scroll -- all via BIOS INT 10h through the
DOS HAL, with the screen buffer in far memory.
Changes:
- tui.h: GW_FAR macro (expands to __far on 16-bit, nothing elsewhere),
tui.screen declared as tui_cell_t GW_FAR *
- tui.c: _fcalloc/_ffree for 16-bit, _fmemmove for scroll_up()
- TUI_CELL() macro works unchanged (far pointer dereference is
transparent)
platform/hal_dos.c: DOS HAL implementation using BIOS INT 10h for
screen/cursor, INT 16h for keyboard, direct character output via
BIOS write-char. Compile-time selection via __MSDOS__ define.
Linux HAL (hal_posix.c) unchanged -- full backward compatibility.
hal.h: add hal_dos_create() declaration under __MSDOS__ guard.
main.c, gwrt.c: select HAL at compile time via #ifdef __MSDOS__.
Makefile.dos: OpenWatcom wmake build file targeting DOS/4GW 32-bit.
Builds GWBASIC.EXE (interpreter), GWBASCOM.EXE (compiler),
GWRT.LIB (runtime library for compiled programs).
All 72 interpreter, 14 kernel, and 69 compiler tests continue to
pass on Linux (no regression).
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.
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.
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.
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.
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$(0) + scan_code two-byte sequences per
the IBM PC convention. Refactored event trap key parsing to use tui_read_key()
instead of duplicating escape sequence parsing.
Golden-file regression tests: generated .expected output files for 55 of 58
test programs (3 timing-dependent tests excluded). The test runner now
reports compat match status alongside pass/fail.
Classic programs: added Hamurabi, Lunar Lander, Gunner, and Diamond from
David Ahl's BASIC Computer Games (1978) in tests/classic/ for manual
compatibility testing.
Docs updated with compiler roadmap item and hardware I/O simulator plan.
Add event-driven programming: ON TIMER(n) GOSUB with TIMER ON/OFF/STOP,
ON KEY(n) GOSUB with KEY(n) ON/OFF/STOP for F1-F10. Fix F-key escape
sequence parser (F9/F10 detection, push back consumed bytes on unmatched
sequences). Add EDIT statement for TUI line editing. Guard key trap
polling so keystrokes aren't consumed when no traps are configured.
LPRINT and LLIST now output to a printer device or file instead of the
screen. By default, output is appended to LPT1.TXT in the current
directory. Use --lpt to redirect to a real printer device (/dev/lp0,
LPT1 on FreeDOS) or a custom file path.
Includes full PRINT format support (semicolons, commas, TAB, SPC,
PRINT USING) and LLIST with line number range parsing.
The TUI screen buffer is now dynamically allocated instead of using a
fixed 25x80 array. When launched with --full/-f, the editor queries the
terminal size via ioctl(TIOCGWINSZ) and adapts accordingly. The default
remains the authentic 25x80.
AUTO generates line numbers during interactive editing, RENUM
renumbers program lines and patches all GOTO/GOSUB/ON references,
DELETE removes line ranges. COMMON declares variables preserved
across CHAIN. Also fixed LIST/DELETE range parsing (was broken by
expression evaluator consuming the dash as subtraction).
Bump to v0.7.0, 53 tests.
DATE$, TIME$, and TIMER now return real system date/time instead of
hardcoded values. Added directory and shell access statements with
proper GW-BASIC error codes (Path not found 76, File already exists 60).
Bump to v0.6.0, 52 tests.
Authentic GW-BASIC screen editor with 25x80 buffer, free cursor movement,
enter-on-any-line, F1-F10 function keys, Insert/Overwrite toggle, KEY
ON/OFF/LIST statement, and Ctrl+Break handling. HAL pointer swap routes
all PRINT/LIST/error output through the TUI automatically. Piped mode
unchanged (50/50 tests pass).
Adds automated compatibility testing infrastructure: DOSBox-X headless
config, PRINT-to-file transform script, and run_compat.sh with --generate
and --compare modes for verifying output against real GWBASIC.EXE.
Project renamed from gwbasic-c to GW-BASIC 2026.
Add GitHub Actions CI with automated build and test. Implement real
terminal I/O with raw mode (enable_raw/disable_raw, proper INKEY$
polling via VMIN=0/VTIME=0, INPUT$ function). Add Sixel graphics
engine with virtual framebuffer (SCREEN 1: 320x200, SCREEN 2:
640x200), Bresenham line drawing, midpoint circle, flood fill PAINT,
DRAW mini-language parser, and Sixel encoder with RLE. Replace all
graphics stubs with real implementations (PSET, LINE, CIRCLE, DRAW,
PAINT, COLOR, SCREEN, POINT). Fix AND/OR/XOR operator precedence
to be lower than relational operators. Add 13 classic test programs
(39 total). Bump version to 0.5.0.
Add CHAIN statement for loading and running chained programs with
optional ALL flag to preserve variables. Extend RUN to accept a
filename string argument. Implement random-access file I/O with
FIELD, LSET, RSET, PUT#, GET# and the MBF conversion functions
CVI/CVS/CVD/MKI$/MKS$/MKD$. Add COMMON statement (parse and skip).
Five new test programs covering all new features (27 total).
Add OPEN/CLOSE with both modern (OPEN "f" FOR OUTPUT AS #n) and compact
(OPEN "O",#n,"f") syntaxes. PRINT#, WRITE#, INPUT#, LINE INPUT# for
sequential file access. EOF() now returns real file status with peek-ahead.
LOC/LOF return approximate values.
PRINT USING with numeric (#, ., +, -, $$, **, ^^^^, comma grouping) and
string (!, &, \ \) format specifiers. Shared by PRINT USING and PRINT# USING.
SAVE (ASCII), LOAD (with ,R auto-run), and MERGE for program persistence.
MID$ assignment (MID$(var$, start [,len]) = expr) for in-place string
modification. Works with both scalar variables and array elements.
Graphics stubs for SCREEN, PSET, PRESET, LINE, CIRCLE, DRAW, PAINT,
VIEW, WINDOW, PALETTE - parse and discard arguments so graphics-heavy
programs don't crash.
SYSTEM and NEW/CLEAR now close all open files. Version bumped to 0.3.0.
22 tests pass (16 existing + 6 new).
Add variable storage (scalar and array), program line storage with
RUN/LIST/NEW, and full control flow: FOR/NEXT, GOTO, GOSUB/RETURN,
IF/THEN/ELSE, WHILE/WEND, ON GOTO/GOSUB, DATA/READ/RESTORE.
New modules: interp.c (1445 lines - execution loop and statement
dispatcher), vars.c, arrays.c, input.c. Version bumped to 0.2.0.
16 test programs pass including Leibniz pi and prime sieve.
GW-BASIC reimplementation in C11, using Microsoft's open-sourced 8088
assembly as the authoritative reference.
Tokenizer (CRUNCH/LIST), expression evaluator with operator precedence,
all math functions (SIN, COS, TAN, ATN, SQR, LOG, EXP, RND, etc.),
string functions (LEFT$, RIGHT$, MID$, CHR$, ASC, VAL, STR$, etc.),
PRINT statement with comma/semicolon zones, TAB(), SPC().
Handles integer/single/double types with correct promotion, D exponent
for double-precision literals, type suffixes (%, !, #), &H hex/&O octal
literals, MBF conversion routines, and GW-BASIC-compatible number
formatting.
Platform-independent via HAL vtable; POSIX backend included.
