# XPT Version 8
This module is reserved for future XPT v8 implementation.
## Key Differences from V5
XPT v8 (also known as extended transport format) differs from v5 in several ways:
### Variable Names
- V5: Maximum 8 bytes
- V8: Maximum 32 bytes
### Labels
- V5: Maximum 40 bytes
- V8: Maximum 256 bytes
### Header Structure
- Different magic strings and header record layouts
- Extended NAMESTR format to accommodate longer names
### Character Set
- V8 typically uses UTF-8 encoding
- V5 traditionally uses ASCII/Latin-1
## Implementation Status
**Not Implemented**
The API is ready for V8 selection (`XptVersion::V8`), but attempting to
read or write V8 files will return `XportrsError::UnsupportedVersion`.
## When to Use V8
V8 is useful when:
- Variable names exceed 8 characters
- Labels exceed 40 characters
- UTF-8 support is required
However, note that many regulatory submissions still require V5 format
for compatibility with older SAS versions.
## Future Implementation
When implementing V8 support, the following modules will be needed:
```
v8/
mod.rs
constants.rs # V8 magic strings and markers
namestr.rs # Extended NAMESTR format
read/
mod.rs
reader.rs
parse.rs
write/
mod.rs
writer.rs
```
## References
- SAS documentation on extended transport format
- CDISC guidance on XPT versions