Two different releases of mosflm for you to read about:

The MRC Cambridge version:

http://www.mrc-lmb.cam.ac.uk/harry/mosflm/mosflm_user_guide.html


The MacCHESS version with DPS in front:
 
http://staff.chess.cornell.edu/%7Eszebenyi/proc_gui/proc_gui_tutor.html