https://github.com/dagrigorev/gw-basic-cpp
Rewritten version of GW-BASIC in C++20
https://github.com/dagrigorev/gw-basic-cpp
basic cmake cpp cpp20 easter gwbasic snake
Last synced: 3 days ago
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Rewritten version of GW-BASIC in C++20
- Host: GitHub
- URL: https://github.com/dagrigorev/gw-basic-cpp
- Owner: dagrigorev
- Created: 2026-04-21T20:46:25.000Z (about 1 month ago)
- Default Branch: main
- Last Pushed: 2026-05-16T17:19:51.000Z (16 days ago)
- Last Synced: 2026-05-16T19:14:59.491Z (16 days ago)
- Topics: basic, cmake, cpp, cpp20, easter, gwbasic, snake
- Language: C++
- Homepage:
- Size: 706 KB
- Stars: 3
- Watchers: 0
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
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README
# GW-BASIC (Modern Cross-Platform Rewrite)
A modern, cross-platform rewrite of the classic **GW-BASIC interpreter**, implemented in **C++20** with a real-time execution model and hardware-accelerated graphics.
This project aims to preserve the simplicity and spirit of GW-BASIC while providing a clean, extensible architecture suitable for modern systems.
---
## ✨ Features
### 🧠 Language Support
* Line-numbered BASIC programs
* Immediate mode (REPL) + file execution
* Control flow:
* `IF ... THEN ... ELSE`
* `GOTO`, `GOSUB`, `RETURN`
* `FOR/NEXT`
* `WHILE/WEND`
* Variables:
* Numeric + string
* Arrays (`DIM`, `ERASE`, `OPTION BASE`)
* Default typing (`DEFINT`, `DEFSTR`, etc.)
* Expressions:
* Arithmetic
* Exponentiation (`^`)
* Integer division (`\`) and `MOD`
* Logical (`AND`, `OR`, `NOT`)
* User-defined `DEF FN` functions
* Functions:
* `ABS`, `INT`, `LEN`, `VAL`
* `FIX`, `CINT`, `CLNG`, `CSNG`, `CDBL`, `SGN`, `SQR`, `SIN`, `COS`, `TAN`, `ATN`, `EXP`, `LOG`
* `RND`
* `DATE$`, `TIME$`, `TIMER`
* String functions (`LEFT$`, `RIGHT$`, `MID$`, `UCASE$`, `LCASE$`, etc.)
---
### 🎮 Real-Time Engine
* Frame-based execution model
* Non-blocking input (`INKEY$`)
* Engine tick integration
* Batch rendering for high-performance drawing
* Suitable for games and simulations
---
### 🖥 Graphics
#### Rendering Backends
* **Windows** → Direct3D 11
* **Linux** → OpenGL (X11)
* **Headless** mode for testing / CI
#### Graphics API
* `SCREEN`
* `CLS`
* `COLOR`
* `LOCATE`
* `PSET`, `LINE`, `CIRCLE`
* `PAINT`, `DRAW`
* `GET` / `PUT` (graphics blocks)
* `VIEW`, `WINDOW`, `PMAP`
* `PALETTE`, `PALETTE USING`
#### Features
* Pixel canvas abstraction
* Palette remapping
* Viewport and world-coordinate transforms
* Hardware-accelerated presentation
* Aspect-preserving window scaling
* Automatic batching for performance
#### Examples
Here is example of graphics
`tan(x^2 + y^2) = 1` graph example:
`snake game` example:
`easter card` example:
`y=sin(x), y=cos(x)` graphs:
`norton commaner` inspired example:
---
### 📁 File I/O
* `OPEN`, `CLOSE`
* `INPUT#`, `PRINT#`, `WRITE#`
* `LINE INPUT#`
* `EOF`, `LOF`, `LOC`
* `KILL`, `NAME`, `MKDIR`, `RMDIR`
---
### 🎹 Input
* `INKEY$` (non-blocking)
* Keyboard input from:
* Console
* Native graphics window (Win32 / X11)
---
## 🚀 Getting Started
### Build
#### Requirements
* C++20 compiler
* CMake ≥ 3.16
#### Linux
```bash
cmake --preset debug
cmake --build --preset debug
ctest --preset debug
```
#### Windows (MSVC)
```powershell
cmake --preset debug
cmake --build --preset debug --config Debug
ctest --preset debug -C Debug
```
---
## ▶️ Usage
### Run interpreter (REPL)
```bash
gwbasic
```
### Run BASIC file
```bash
gwbasic --file ./examples/snake.bas
```
### Console editor
```bash
gwbasic --edit ./examples/snake.bas
```
The editor accepts numbered BASIC lines directly and supports commands such as
`RUN`, `CHECK`, `LIST`, `OPEN `, `SAVE [file]`, `EDIT `,
`DEL `, `RENUM`, `NEW`, and `QUIT`.
### Headless mode (no graphics window)
```bash
gwbasic --headless --file ./examples/snake.bas
```
### Syntax check without running
```bash
gwbasic --check --file ./examples/snake.bas
```
Inside the REPL or a BASIC program, text source can be persisted with:
```basic
SAVE "program.bas"
LOAD "program.bas"
```
---
## 🧪 Example
### Snake Game
```bash
gwbasic --file ./examples/snake.bas
```
Features:
* real-time gameplay
* keyboard control via graphics window
* hardware-accelerated rendering
More examples are listed in [examples/README.md](./examples/README.md).
---
### Math Plot
```basic
10 SCREEN 2
20 CLS
30 COLOR 15,0
40 CX = 320: CY = 100
50 SX = 0.03: SY = 0.03
60 FOR PY = 0 TO 199
70 FOR PX = 0 TO 639
80 X = (PX - CX) * SX
90 Y = (PY - CY) * SY
100 IF ABS(TAN(X*X+Y*Y)-1) < 0.05 THEN PSET (PX,PY), 10
110 NEXT PX
120 NEXT PY
130 END
```
---
## 📚 Compatibility
See [docs/compatibility.md](./docs/compatibility.md) for the current supported
GW-BASIC statements/functions, known differences, and test coverage.
### API Documentation
If Doxygen is installed, generate developer API docs with:
```bash
cmake --preset docs
cmake --build --preset docs
```
---
## 🏗 Architecture
### Core Components
#### Interpreter
* Lexer → Parser → AST → Execution
* Line-numbered program storage
* Immediate + stored execution modes
#### Runtime
* Variable storage
* Array memory
* File handles
* Graphics state
* Engine tick integration
#### Graphics
* In-memory pixel canvas
* Platform-specific presenter:
* D3D11 (Windows)
* OpenGL (Linux)
* Batch rendering system
#### Engine Loop
* Cooperative execution
* Frame pacing (~60 FPS)
* Event pumping
* Input polling
---
## ⚡ Performance Notes
* Rendering is **batched**, not per-pixel immediate
* Large plots are now significantly faster than naive implementations
* Still an interpreter → heavy numeric loops can be slow
* Prefer:
* coarse stepping
* analytical drawing (e.g., circles instead of brute-force)
---
## ⚠️ Limitations
* Not a 100% GW-BASIC clone
* Graphics are **portable abstractions**, not exact hardware emulation
* Some legacy quirks are not implemented
* Floating-point math is modernized (not 8087-compatible)
* Performance depends on interpreter speed
---
## 🛠 Roadmap
* Fixed-timestep VM scheduler
* More BASIC compatibility edge cases
* Improved parser tolerance
* Sound subsystem (`PLAY`, `SOUND`) improvements
* Better console emulation
* Optional SDL backend
* Debug / trace mode
---
## 🤝 Contributing
Contributions are welcome.
Focus areas:
* language compatibility
* performance improvements
* platform backends
* test coverage
---
## 📜 License
Under MIT license
---
## 🎯 Vision
This project is not just a clone.
It’s a **modern BASIC runtime**:
* simple like the original
* powerful enough for real-time programs
* portable across platforms
* clean and extensible in design