Ok, I've found a description of the .rb format in manual 093-000081-02 for the Macro Assembler, and a description of the .ab format in manual 093-000003-06 for the Binary Loader. Now, off to dig into Toby's assembler some more to figure out how to make it emit absolute binary! -- Mark J. Blair, NF6X <nf6x at nf6x.net> http://www.nf6x.net/