Here are some notes on the usage of the flash filesystem on the LegoMindstorms NXT controller.
File names can be up to 19 characters long, and are case-insensitive. There is no directory hierarchy; all files are kept in a single top-level directory. The on-board interface shows files grouped into various categories, like “Software files”, “Try Me” etc—these groupings are based purely on the filename extension.
| Category | File Contents | Extension |
| Datalog files | text files containing sensor data | .log |
| NXT files | ? | .rpg |
| Software files | executable bytecode programs | .rxe |
| Sound files | sound sample files; melody files | .rso |
| Try Me | executable bytecode programs | .rtm |
Filenames ending with other extensions are not visible to the user through the on-board interface, but they can still be accessed programmatically.
2 pages link to NXTFilesystemNotes:
