If you are using a more recent computer but somehow using an old DOS interface and not in an emulator, then you can use 32-bit instructions in Real Mode. An operand size instruction 66h is inserted before an instruction to command the processor to do a 32-bit operation instead of a 16-bit instruction. BUT this allows you to do 32-bit math. Memory addressing is done with a 67h but not applicable as in 16-bit mode when in Real mode.