What is the memory representation of *Array?

 
Hi,

I am trying to understand how the VM make the distinction between  
ByteArray WordArray ByteString and Array.
I look at #commonAt:Put:, #commonAt: and  
#commonVariable:at:put:cacheIndex: #commonVariable:at:cacheIndex:.

I see that ByteArray and ByteString a handle quite the same way except  
that there is a #asciiOfCharacter: and #characterForAscii:.
And Array use either  storePointer or storeLong32 (fetchPointer,  
fetchLong32 respectivily).

Then I don't see the case of the WordArray.
Could someone enlighten me?

Thanks
        Mth