NXC

Not eXactly C (NXC) is a high level language, similar to C, developed by John Hansen. The program can be written in this language and compiled in rxe file that can be executed directly in the NXT. You need a text editor, the compiler and a tool for upload the file on the NXT. These things can be done with a single software on Windows: Bricx Command Center (BricxCC).

See John Hansen's pages: BricxCC and NXC/NBC