Operand Size ?

hi, I am new to Asm.
EAX value is contain pointer to memory

cmp [EAX], 65h

how do I know if it's compare byte, word or dword operand size ?

how to make sure that the compare is in byte size not in dword ?

Note : using MASM (VS .Net)

I think the following syntax is working with Masm:

Code:

---

cmp byte ptr [EAX], 65h

or

cmp word ptr [EAX], 65h

or

cmp dword ptr [EAX], 65h

---