DASM is a macro data assembler, meaning that it assembles binary data, not executable code. DASM supports macros, symbols, and expressions which can be used to extend the basic feature set enough that you can write human readable "code" then assemble it.
im using dasm for coding demos on the atari 2600/vcs. its a very great tool. big thanks to matt dillon for that tool. :-)
Works great and without problems.