Is there any format for a .com that isn't just a headerless chunk of x86 code?? (Which also means it's extremely difficult to determine if a .com file really i

Is there any format for a .com that isn't just a headerless chunk of x86 code?? (Which also means it's extremely difficult to determine if a .com file really is an executable--there's no signature. It either decodes or it doesn't--and most bytes decode correctly because you want to pack the commands in as densely as possible. Things which will not decode are packing inefficiencies.) (And back from the Z80 days I remember very carefully crafting assembly code that could be embedded in a BASIC program without causing it to puke. Some commands were unavailable and some values were not permitted--amongst them, zero.)