# BT constants

## Function

 reads the compile-time constants and lightweight cache constants of the current BT runtime.

## Syntax

```bt
BT.VERSION
BT.NAME
BT.OS
BT.THREADS
```

## Parameters

| Parameters | Type | Required | Default value | Description |
| ------ | ------ | ------ | ------ | ------ |
| None | - | No | None | Constant properties require no parameters. |

## Return Value

| Constant | Type | Description |
| ------ | ------ | ------ |
| BT.VERSION | String | The current BT version. |
| BT.NAME | String | Current binary logical name, usually `bt` or `bt_app`. |
| BT.OS | String | Operating system name, such as windows, linux, macos. |
| BT.ARCH | String | CPU architecture, such as x86_64, aarch64. |
| BT.FAMILY | String | Operating system family, such as windows, unix, wasm. |
| BT.DEBUG | Bool | Whether to build for debug. |
| BT.EXE_EXT | String | Current platform executable file extension, such as `.exe` or empty string. |
| BT.LIB_EXT | String | Current platform dynamic library extension, such as `.dll`, `.so`, `.dylib`. |
| BT.POINTER_WIDTH | Int | Pointer width, usually 32 or 64. |
| BT.THREADS | Int | Number of available parallel threads, cached after first read. |

## Examples

```bt
version = BT.VERSION

// Output: 1.1.0
print version
```

## Notes

- BT constants are read-only properties.
 - BT.THREADS uses runtime caching and does not query the system repeatedly on each read.