regarding function

Code:

  [B] PDEV[/B] *get_dfprt(register mydnum flx)
{
	u_short ctr;
	DUPNUM *dptr = &GDFNUM[0];
	for(ctr=0;ctr<DFNUM_EN;ctr++,dptr++)
	{
		if(dptr->num == flx)
			return(&dptr->pd);
	}
	return((PDEV *)0);
}

where PDEV is a structure & having some members

Iam not getting this function definition ,what does it means

PDEV *get_dfprt(register mydnum flx)

 

mydum is unsigned long