APPC (Advanced Program-to-Program Communication, sometimes called LU 6.2) is a communication protocol and programming interface standard that operates in the presentation layer (the layer that ensures that messages are in the proper format for the recipient) and the session layer (the layer responsible for setting up and taking down the association of the two end points in a connection) of the Open Systems Interconnection (OSI) communications model. Originally developed by IBM as a remote transaction processing tool, APPC is now used to provide distributed services within a heterogeneous computing environment.
APPC software enables high-speed communication to take place between programs residing on different computers, and between workstations and midrange and mainframe computer servers. APPC is an open standard that is supported on most platforms.
APPC is based on IBM's Systems Network Architecture (SNA).