Now that I think of it, I do think of it as 1-to-1 substitution, but it is not completely trivial - when transforming to machine code, you do generally have to

Now that I think of it, I do think of it as 1-to-1 substitution, but it is not completely trivial - when transforming to machine code, you do generally have to keep track of where in the code you are to know whether to try to transform an assembly language token into a machine language opcode or into some other sort of machine language value.