dvips xx converts to postscript and
prints filename xx on default lpr printer.
dvips -o xx creates a file called xx.ps, no printing.
Subsequently the xx.ps postscript file
can be printed with lpr.
dvips -o yy xx creates a file in postscript format called yy,
no printing.
For further information in this area you should refer to the CERN guide called 'TEX at CERN' by Michel Goossens, available on self-service in the UCO.