The HP 82938A HP-IL Interface was a short-range interconnection bus or network introduced by Hewlett-Packard in the early 1980s. It enabled many devices such as printers, plotters, displays, storage devices (floppy disk drives and tape drives), test equipment, etc. to be connected to programmable calculators such as the HP-41C, HP-71B and HP-75C/D, the 80-series and HP-110 computers, as well as generic ISA bus based PCs.

When the HP-IL (Interface Loop) connects the HP Series 80 Personal Computer to an interface loop, many devices can communicate with each other. Communication over the two-wire loop is asynchronous and serial, with digital messages travelling from one device to the next around the loop in one direction only. Each device in the loop had a pair of two-wire connections, one designated in, which received messages from the previous device in the loop, and one designated out, which delivered messages to the next device in the loop. 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.