Comment by ptspts

fasm is indeed great. It has many features, it can do all the code size optimizations, it even knows the sizes of variables (e.g. `mov myvar, 5` depends on `myvar db 0` vs `myvar dw 0`). NASM and fasm syntax are quite similar.

NASM supports more output file formats (i.e. .o files for many systems), and it can receive macro definitions from the command line (e.g. `nasm -DDEBUG`).