[ECOS] A simple data type question

[HuangQiang]

Hi all:
   Could anyone give me some detail about the following statement:

	#define IOPDATA		((volatile unsigned *)(SYSCFG + 0x5008))

if I change the *IOPDATA = 0x0; then how many bit can I change . what data
width is the (volatile unsigned *)? if I want to use a 32-bit width pointer
how can I do it?

Thanks all.