com to bin?

Short answer: NO.

.com and .bin programs are loaded in different memory areas, and are built to operate in a (software-wise) very different environment.

If you have source code for a program, it may be possible to adapt one to the other. But that might be a lot of work, though.

You meant .com, or .rom? And what do you mean with "big size"?

Perhaps you could explain your problem a bit more detailed, what are you trying to achieve?