The DL_POLY_2 parameters file for version 2.10 (and earlier) contains all the parameters defining the arrays dimensions of DL_POLY_2 plus the fundamental constants and conversion factors. In the include file for version 2.11 (and after) the bulk of these parameters take the form of FORTRAN integer variables, which are stored in the COMMON block /params/. Apart from this difference, the meaning and function of the parameters is the same. The DL_PARAMS.INC file is included in all relevant subroutines at compile time.