**************************************************
* System Call: F$SUser
*
* Function: Set User ID number
*
* Input:  Y = Desired user ID number
*
* Output: None
*
* Error:  CC = C bit set; B = error code       
*
FSUser   ldx   <D.Proc      get current process dsc ptr
         ldd   R$Y,u        get requested user number
         std   P$User,x     save new user # in process descriptor
         clrb               no error
         rts                and return
