Information systems  Unit 2 direct files  Unit 3 indexed files 

 - London  Open University  1988 
 - 27p.  27cm 
<br/><br/><label>ISBN: </label>0335143369 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Data files and databases
<br/><br/><label>Dewey Class. No.: </label>005.74  / OPE