The FT-818 ( and FT-817) use a serial port with an 8 pin mini-DIN connector at the radio end. The same cable can be used for programming and rig control.
The official Yaesu part number is CT-62. The CT-62 has an RS-232 serial connector on the computer end, and you will need a USB to serial adapter as well with that cable.
I use the valley enterprises cable. This cable includes the USB to serial adapter.
There are other cable options out there.
mike, kj6vcp