Please, stick to just one question per post - otherwise your replies will get very confused, as you can't tell from the Subject line which one is being addressed!

"Can you tell me what is the difference between motorola and infineon at the numbers representation?"

Are you asking about the Big/Little-endian question? If so, see here:
http://www.8052.com/forum/read.phtml?id=14223

"Motorola Format" is usually taken to mean big-endian; see here:
http://www.8052.com/forum/read.phtml?id=14250

As for Infineon, that might well depend on which particular Infineon processor and/or toolset you're thinking about!
Read the manuaus/datasheets.

Note that the 8051 itself doesn't support numbers >8 bits, so this depends entirely upon the particular implementation.
Similarly for floating-point.

Keil's C51 is generally big-endian, but you'll need to read the section in the manual on "Byte Ordering" for full details.


"Also, can you tell me what is the difference between an emulator and a simulator?"

this has already been discussed ad nauseam in this forum - use the 'Search' button!