BT is a compact interpreted programming language implemented in Rust. Its JavaScript-like syntax compiles to register-based bytecode, while one shared runtime powers command-line programs, web services, desktop applications, native FFI, and installable extensions.
## Highlights
- **Familiar syntax** — JavaScript-like expressions, functions, classes, closures, destructuring, and chainable APIs.
- **Register-based VM** — source code is compiled to bytecode before execution.
- **One runtime, multiple targets** — build CLI tools, concurrent web services, and packaged desktop applications.
- **Explicit empty-value model** — `empty` means that no value exists; `null` remains an explicit value.
- **Extensible by design** — use native FFI, WASM/WASI extensions, pure BT extensions, and object bindings.
- **Long-running workloads** — bounded runtime resources and observable statistics support resident services.
## A first look
```bt
fn greet(name) {
'Hello, ' + name
}
// Output: Hello, BT
print greet('BT')
```
Every BT expression has a runtime result. Multiline blocks return their last statement by default, and `return` can still exit a function early.
BT also distinguishes two empty states:
- `empty` means that a value does not exist, such as a missing field, an out-of-range index, or a function without a result.
- `null` is an explicit value used for JSON nulls, database NULLs, or failed conversions.
## Quick start
Install the stable Rust toolchain, then run a checked-in BT example directly from the repository:
```text
cargo run --release --bin bt -- -c examples/compat/empty-null.bt
```
When the current directory contains `main.bt`, running `bt` without a source argument executes that file. Otherwise, it starts the interactive prompt.
Run the basic desktop example:
```text
cargo run --release --features desktop --bin bt-app -- run examples/desktop
```
### Install the interpreter for your user account
This feature is pending the next release. With a build containing it, run `./bt install` on Linux/macOS or `.\bt.exe install` in Windows PowerShell from the extracted directory. Use `bt update` to check the official website and update an existing user installation to the latest stable release. At the `bt>` interactive prompt, enter `install` or `update`. The former `--install` alias is removed. Use `bt update 
