One of the assemblers I saw mentioned above is one I particularly like: TASM. Multi-target, multiple host versions (DOS, Win32, Win64). It has been my go-to for over 20 years, although I've used a bunch of others, mostly because I don't want to re-write the original source to fix syntax, etc. Beyond that, I use NASM, MASM, various gcc compilers for different projects. Obviously some are more flexible than others and/or have different features needed for a specific purpose. For one project, I had to even dip into an original ASM from Seattle Computer because it had a unique encoding method that was needed for a specific recreation project.
Rich Cini
