A very simple way is to use FCOPY with the compare option.
FCOPY FROM=A;TO=B;COMPARE=10
Not very sophisicated though. It does leave both files unchanged.
*-----------------------------------------------------------*
* Ronald Darling, Data Processing Supervisor *
* New Mexico Tumor Registry/Epidemiology and Cancer Control *
* Univeristy of New Mexico Health Sciences Center *
* 2325 Camino de Salud, NE *
* Albuquerque, NM 87131-5306 *
* [log in to unmask] *
* (505) 272-8580 *
*-----------------------------------------------------------*