compare with unknown value malware disassembly ?

[kb432]

1)

cmp dword_4298B8, eax
jnz short loc_xxxx

dword_4298B8 is initialized as "dd ? "

then how to compare with eax?
dword_4298B8 --->  dd ?

 

2)
Can you give me an example of array and accessing it and allocating it in ASM when i do reverse egnineering! 
Thanks
 

3) 

mov WORD PTR [ebx], 2

WHAT IS THIS ABOVE "WORD PTR"  ? 

[evlncrn8]

dword is initialized as dd ? which means its uninitialised memory, filled at runtime by something

cmp dword ptr [0x12345678], eax would be such a comparison

DWORD ptr points to a dword, so the comparison is dword

WORD ptr points to a word, so the comparison is word

BYTE ptr points to a byte, so the comparison is a byte

theres others like qword ptr, tbyte ptr and so on... this is pretty much asm 101 though, so i'd suggest you go read some asm books