to be connected to programmable calculators such as the HP-41C, HP-71B and HP-75C/D, the Series 80 and HP-110 computers, as well as generic ISA bus based PCs.

HP-IL cables utilize a unique two-pin connector design with polarizing D-shaped shells, and can be connected together without further adapters to extend their length.

When the "Auto Address n" message finally returns to the controller, it can tell how many devices are on the loop (n-1).

There were also plans to make test equipment with IL interfaces, but apart from the somewhat popular 3468A multimeter, only a few devices were introduced before HP-IL itself became obsolete.

For ease of use, the calculators supported automatic I/O address assignment ("AUTOIO"), where printer or mass storage commands are directed to the first available device of the appropriate type.

Where multiple devices per type were present, a manual ("MANIO") assignment mode could be used.