XA is a high-speed, two-pass portable cross-assembler. It understands mnemonics and generates code for NMOS 6502s such as 6502A, 6504, 6507, 6510, 7501, 8500, 8501, 8502. Key amongst it's features: C-like preprocessor, rich expression syntax supports o65 re-locatable objects with a full linker and relocation suite, as well as "bare" plain binary object files block structure for label scoping. This program is available for linux / unix users.