Boss 5 RS-232 wiring

I have an old Bridgeport Boss 5 with all the original electronics
(can't afford an upgrade) When I bought it the seller told me he
was running it on Bobcad by wiring from the printer port on a PC to
the 8-pin RS-232 port on the machine, but he didn't have a cable to
do this with, he used a piece of telephone wire with the ends stuck
in the right holes (he said you only need three pins anyway) I
can't get any more info from him, and I need the pinouts. I don't
know how to set the machine to send or recieve data either. Can
anybody help?

Thanks
Nathan