The HP-86 series was the same machines as the HP-87 but used a 9" or 13" external monochrome monitor.
The built-in BASIC language derived from the HP-85's but featured about 20 additional graphics commands. It also allowed to directly address the ports of external modules.
Two vdersions were successively released:
The 86-A had 64 KB of RAM and was fully compatible with the 87-A. It had built-in interfaces for a printer and dual floppy drives. Internally, these interfaces were seen as HP-IB devices.
The 86-B had 128 KB of RAM and an HP-IB port instead of the printer/fDD interfaces. It was the same machine as the HP-87XM, but with an external monitor.
There was no special operating system. The Basic interpreter provided all the necessary commands for I/O and peripherals management.
Notice that the HP-IB interface found on almost all HP computers - from micro to mini - is a special version of the well-known IEEE 488 interface.