Source: Manuel Bilderbeek
Z80ASM is a Z80 assembler written in Ansi C, released under GPL. The project has recently been added to the testing and unstable repositories of
Debian Linux. The assembler aims to be portable and complete and assembles all official mnemonics. Apart from that. it also aims to assemble the unofficial mnemonics.
Relevant link:
Z80ASM project summary
since many cool programs/demos use those ...